Influence of Process Parameters on Geometry and Thermal Behavior in Wire Laser Cladding of Bronze on Stainless Steel Substrates

Abstract

Wire laser cladding (WLC) of bronze on stainless steel offers a promising approach for combining the structural strength of steel with the superior tribological and corrosion properties of copper alloys. In this study, the influence of key process parameters, including wire preheating current, deposition speed, laser power, and wire feed speed on melt pool temperature and clad geometry was investigated using response surface methodology (RSM). Experiments were performed using a robot-assisted coaxial wire feeding laser cladding system, and real-time thermal monitoring was conducted using an infrared camera. The results showed that defect-free bronze clads with good metallurgical bonding and limited dilution were achieved across the investigated parameter range. Statistical analysis revealed that melt pool temperature is primarily governed by laser power and deposition speed, with a significant interaction between these parameters. Clad height was mainly influenced by wire feed speed and deposition speed, whereas clad width was controlled by laser power and deposition speed. The side angle was affected by deposition speed, laser power, and wire feed speed, reflecting the balance between vertical buildup and lateral spreading. Overall, the study demonstrates that stable and high-quality clads can be achieved by properly balancing energy input and material supply. The developed models provide valuable insight for optimizing process parameters in wire laser cladding of bronze on stainless steel.

1. Introduction

Surface modification technologies play a fundamental role in improving the functional performance and service life of engineering components operating under severe mechanical, thermal, and corrosive conditions [1,2,3]. In many industrial applications, the bulk material of a component is selected primarily for its structural strength and load-bearing capacity, whereas the surface must provide specific properties such as wear resistance, corrosion resistance, or improved tribological behavior [4,5]. Consequently, the development of reliable surface engineering techniques has become essential for extending component lifetime and improving operational efficiency.

Copper and copper-based alloys, particularly bronze alloys, are widely employed as surface materials because of their excellent thermal conductivity, corrosion resistance, and favorable tribological properties [6,7,8]. Bronze coatings are commonly used in components subjected to sliding contact and frictional loading, including bearings, bushings, marine components, and electrical contact systems [9,10]. Depositing bronze or Cu-based alloys onto steel substrates enables the combination of the high mechanical strength of steel with the desirable surface properties of copper alloys, making such material combinations attractive for many industrial applications [11,12].

Among various surface modification techniques such as thermal spraying [13], welding overlays [14], and electroplating [15], laser cladding [16,17,18] has attracted considerable attention due to its ability to produce high-quality coatings with strong metallurgical bonding to the substrate. The process involves localized melting of both the feed material and a thin layer of the substrate using a high-energy laser beam, allowing for the formation of dense coatings with controlled dilution and limited heat input. In addition, the rapid heating and cooling conditions associated with laser processing often lead to refined microstructures, which can further enhance the mechanical and tribological performance of the deposited layer [19,20].

Different studies have investigated the deposition of bronze and copper-based alloys by laser cladding in order to enhance surface properties. González et al. [21] demonstrated the feasibility of producing phosphor bronze coatings on alloy steel through laser cladding as an alternative to conventional shrink-fitted bronze bushings. Their results showed that dense coatings with strong metallurgical bonding and negligible dilution could be obtained, with a microstructure composed mainly of α-dendrites and (α + δ) eutectoid phases. The deposited layer exhibited a hardness approximately 56% higher than that of cast bronze, indicating the capability of laser cladding to improve the mechanical performance of bronze coatings. The influence of process parameters on coating quality has also been investigated in some studies. Yin et al. [22] examined the effect of laser energy density on modified aluminum bronze coatings deposited on stainless steel substrates. Their results demonstrated that energy density significantly affects coating morphology, microstructure evolution, and wear behavior, and an optimal energy density of approximately 42.4 J/mm² produced coatings with improved hardness and reduced wear rate. Laser cladding of bronze alloys has also been studied for specialized applications such as marine component repair. Feng et al. [23] investigated underwater laser cladding of nickel–aluminum bronze coatings using a protective covering system to enable deposition in a full-wet environment. Their study showed that stable coatings with acceptable morphology could be produced underwater, and the resulting microstructures contributed to improved electrochemical behavior compared with coatings fabricated in air.

In addition to parameter optimization, improvements in laser technology have also been explored to enhance copper alloy deposition. Rippa et al. [24] compared blue-light high-speed laser cladding with conventional infrared laser cladding for bronze deposition on steel substrates. Their results demonstrated that the blue-laser process significantly increased deposition efficiency, achieving a substantially higher deposition rate while requiring lower laser power and producing a smaller heat-affected zone.

Most of the studies mentioned above have employed powder feedstock in the laser cladding process. Powder-based laser cladding offers flexibility in material selection and has been widely used in industrial applications. However, powder delivery systems present several limitations, including relatively low material utilization efficiency, potential oxidation of metallic powders, safety concerns associated with powder handling, and instability in powder feeding during deposition [25].

Wire-based laser cladding has emerged as a promising alternative to powder-fed processes. In this approach, the feedstock is supplied in the form of a solid wire that is melted by the laser beam and deposited onto the substrate surface. Compared with powder-based methods, wire laser cladding offers several advantages, including nearly complete material utilization, improved process stability, reduced oxidation and contamination, and lower feedstock cost. Furthermore, wire feeding allows for more precise control of material deposition rate, which improves process repeatability and facilitates industrial implementation [26].

Recent research has begun to explore the deposition of copper-based alloys using wire-feed laser cladding. Guo et al. [27] investigated underwater wire-feed laser cladding of nickel–aluminum bronze coatings and compared the resulting microstructures with those produced in air. Their results showed that the higher cooling rate in the underwater environment produced finer grain structures and increased microhardness due to the formation of β′ phases and a higher fraction of low-angle grain boundaries, while the corrosion behavior remained largely governed by the copper matrix.

Despite these advances, depositing copper-based alloys using wire laser cladding remains challenging due to the high thermal conductivity and reflectivity of copper alloys, which influence laser energy absorption and melt pool stability. Consequently, careful control of process parameters is required to achieve stable deposition and desirable clad geometry. Key parameters include laser power, wire feed speed, deposition speed, and thermal conditions such as wire preheating, which directly affect melt pool temperature and the geometric characteristics of the deposited layer, including clad height, clad width, and side wall angle.

Accordingly, the use of a robot-assisted wire laser cladding system in the present study is consistent with recent developments in automated manufacturing, where optimized robotic tool paths and energy-efficient process planning have been emphasized as important factors for improving sustainability and process reliability [28].

In the present study, wire-based laser cladding of bronze on AISI 304 stainless steel substrates is experimentally investigated. The effects of wire preheating current (WP), wire feed speed (WFS), deposition speed (DS), and laser power (P) on melt pool temperature and clad geometry, including clad height, clad width, and side angle, are analyzed using response surface methodology. The objective of this work is to establish relationships between process parameters and deposition characteristics in order to identify suitable conditions for producing high-quality bronze coatings using wire laser cladding.

This study therefore contributes by investigating the effects of key process parameters in wire laser cladding of CuAl9Ni5Fe3Mn2 bronze on AISI 304 stainless steel and by using real-time infrared thermal monitoring to correlate melt pool temperature with clad geometry and process stability.

2. Materials and Methods

2.1. Materials

The substrate material used in this study was AISI 304 stainless steel, selected due to its widespread industrial application and good corrosion resistance. Prior to deposition, the substrate surfaces were prepared to ensure proper bonding during the cladding process. The feedstock material was a commercially available bronze wire supplied by Meltio, with a nominal composition of CuAl9Ni5Fe3Mn2. The wire had a diameter of 1 mm, an ultimate tensile strength of approximately 565 MPa, and a hardness of about 152 HV. This alloy was selected due to its favorable combination of mechanical strength, corrosion resistance, and tribological performance, making it suitable for surface enhancement applications.

2.2. Wire Laser Cladding Process

Wire laser cladding was performed using a robot-assisted deposition system equipped with a coaxial wire-feeding head from Meltio, Linares, Spain, and a high-power laser with a maximum output power of 1.2 kW and a wavelength of 976 nm, as shown in Figure 1. The laser head was mounted on a multi-axis ABB robotic arm (ABB Group, Zurich, Switzerland), enabling precise control of the deposition path and maintaining a constant standoff distance throughout the process. Cladding experiments were conducted by varying key process parameters, including laser power, deposition speed, and wire feed speed. In addition, wire preheating conditions were adjusted to evaluate their influence on process stability and clad formation. An argon shielding gas with a flow rate of 10 L/min was used to minimize oxidation during deposition. The selected parameter ranges were determined based on preliminary trials to ensure stable melt pool formation and continuous deposition. For all experimental conditions, single-track clads were deposited with a constant track length of 70 mm in a single pass. The laser cladding head was mounted on a six-axis ABB IRB 4600-45/2.05 industrial robot (ABB Group, Zurich, Switzerland) equipped with an ABB IRBP A-500 positioner (ABB Group, Zurich, Switzerland), enabling precise control of the deposition path and workpiece orientation during the process. The ABB IRB 4600-45/2.05 robot used in this study has a positioning repeatability of approximately ±0.05 mm, ensuring accurate and repeatable control of the laser cladding path. A thermal imaging camera was integrated into the experimental setup, as illustrated in Figure 1, to monitor the melt pool and surrounding heat-affected zone in real time. For this purpose, an Optris PI 08M (Optris GmbH & Co. KG, Berlin, Germany) short-wavelength infrared camera was used, featuring a spectral range of 780–820 nm, an optical resolution of 764 × 480 pixels, and a temperature range of 575–1900 °C. Before the cladding experiments, the measured temperatures were checked against an external thermometer using heated metal under comparable conditions, and the observed agreement served as a practical validation of the thermal monitoring setup.

Following data acquisition, the thermal recordings were post-processed to extract the temporal evolution of the melt pool temperature. A representative region of interest (ROI) was selected within the melt pool, and the temperature signal was tracked throughout the deposition process. As illustrated in Figure 2, the recorded temperature data were plotted as a function of time to obtain a temperature–time diagram. To minimize the influence of initial transient effects, only the stable operational region of the process was considered for analysis. A linear trend line was fitted to this region to evaluate temperature stability during deposition. The average temperature within the steady-state interval was then calculated and taken as the representative melt pool temperature for each experimental condition.

2.3. Experimental Design

The experimental design was developed using Response Surface Methodology (RSM) to investigate the influence of key process parameters on the thermal behavior and geometric characteristics of the deposited tracks. Four independent variables were considered: wire preheating current, deposition speed, laser power, and wire feed speed. The wire preheating parameter refers to the electrical current supplied to the wire heating system, expressed in amperes (A). The process parameters were varied within the following ranges: wire preheating current from 5 to 65 A, deposition speed from 3 to 15 mm/s, laser power from 625 to 1125 W, and wire feed speed from 4.5 to 18.5 mm/s. These ranges were selected based on preliminary experiments to ensure stable deposition conditions and to avoid defects such as lack of fusion or excessive melt pool spreading. The experimental matrix consisted of 30 runs, including factorial points, axial points, and repeated center points. The center point condition (35 A, 9 mm/s, 875 W, and 11.5 mm/s) was repeated multiple times in order to evaluate process repeatability and improve the reliability of the experimental results. The response variables considered in this study were melt pool temperature, clad height, clad width, and side wall angle. The complete experimental design matrix, including the combinations of process parameters used in each run, is presented in

Table 1. Experimental runs and corresponding process parameters used in the wire laser cladding study.

Number	Wire Preheating Current [A]	Deposition Speed [mm/s]	Laser Power [W]	Wire Feed Speed [mm/s]
1	50	6	750	8
2	20	12	750	8
3	20	6	1000	8
4	50	12	1000	8
5	20	6	750	15
6	50	12	750	15
7	50	6	1000	15
8	20	12	1000	15
9	35	9	875	11.5
10	35	9	875	11.5
11	20	6	750	8
12	50	12	750	8
13	50	6	1000	8
14	20	12	1000	8
15	50	6	750	15
16	20	12	750	15
17	20	6	1000	15
18	50	12	1000	15
19	35	9	875	11.5
20	35	9	875	11.5
21	5	9	875	11.5
22	65	9	875	11.5
23	35	3	875	11.5
24	35	15	875	11.5
25	35	9	625	11.5
26	35	9	1125	11.5
27	35	9	875	4.5
28	35	9	875	18.5
29	35	9	875	11.5
30	35	9	875	11.5

.

2.4. Material Characterization and Analytical Methods

All samples were characterized to evaluate clad geometry and metallurgical bonding. A 3D optical profilometer (VR-6200, Keyence Corporation, Osaka, Japan) at 180× magnification was used for non-contact analysis of surface morphology, including continuity, uniformity, and possible defects such as waviness or cracks. For microstructural assessment, selected samples were sectioned perpendicular to the cladding direction and prepared using standard metallographic procedures (mounting, grinding, polishing). Cross-sections were analyzed using a digital optical microscope (VHX-7000, Keyence Corporation, Osaka, Japan) at 100× magnification to examine interface features and extract quantitative data. Measurements included bead height, bead width, and contact side angle, which are defined in Figure 3, providing a detailed evaluation of how process parameters influenced clad morphology and bonding quality.

3. Results and Discussion

3.1. Clad Layer Quality

The surface morphology and geometric consistency of the deposited clads were evaluated using 3D profilometry, as presented in Figure 4. Based on the observations, all experimental conditions resulted in successful material deposition, with continuous tracks formed along the substrate surface. This indicates that the selected parameter ranges ensured sufficient energy input to sustain the cladding process. Despite the overall successful deposition, significant variations in clad quality can be observed across the experimental runs. Several samples exhibit highly uniform and continuous tracks with stable geometry along the entire deposition length. In particular, runs 3, 5, 7, 8, 9,10, 13, 15, 17, 18, 19, 20, 21, 23, 26, 28, 29 and 30 demonstrate consistent bead width and height, as well as smooth surface morphology. These characteristics suggest stable melt pool behavior and a proper balance between energy input, material supply, and thermal conditions influenced by wire preheating current and deposition speed. In contrast, some experimental conditions show reduced clad quality, characterized by irregular geometry, fluctuations in bead height, and localized inconsistencies along the track. A clear example is run 27, where the clad appears discontinuous and less uniform compared to other cases. This behavior can be attributed to insufficient material supply relative to the thermal input, as indicated by the low WFS = 4.5 mm/s, which likely led to unstable melt pool conditions. Similar, although less pronounced, irregularities are observed in other runs where the mismatch between deposition speed and wire feed speed affects the continuity of the clad. From a broader perspective, the visual results indicate that clad quality is governed by the interaction between process parameters rather than by any single factor. A balanced combination of deposition speed and wire feed speed is essential to maintain a stable melt pool and ensure continuous material deposition. In addition, adequate laser power is required to sustain proper melting, while wire preheating contributes to improved process stability by reducing thermal gradients and facilitating smoother material transfer.

The cross-sectional micrographs presented in Figure 5 provide detailed insight into the internal geometry and metallurgical characteristics of the deposited clads for all experimental conditions. The images correspond to the cross-section of mid-length of each track and allow for direct comparison of clad morphology under different combinations of process parameters (wire preheating current, deposition speed, laser power, and wire feed speed). From a metallurgical perspective, all samples exhibit sound bonding between the bronze clad and the AISI 304 steel substrate, with no visible signs of cracking, delamination, or major defects. This indicates that the selected process window was sufficient to ensure proper fusion and structural integrity of the deposited material. In addition, the interface between the clad and substrate appears relatively well-defined, suggesting that dilution is limited and that excessive mixing between bronze and steel did not occur. Despite the overall good bonding quality, noticeable variations in clad geometry are observed across the different experimental runs. Significant differences in clad height, width, and side wall angle can be clearly identified, confirming the strong influence of process parameters on the final bead shape. In several cases, the clads exhibit a well-defined and smooth semi-circular profile, indicating stable melt pool behavior and uniform material distribution.

However, some samples display asymmetric clad shapes, where one side of the bead is steeper or more extended than the other. This asymmetry can be attributed to non-uniform melt pool dynamics, which may arise from imbalances between heat input and material supply, as well as local variations in heat dissipation during deposition. Such effects are more pronounced under conditions where the relationship between deposition speed and wire feed speed is not well balanced. Furthermore, variations in laser power and wire preheating current also influence the extent of spreading and penetration. Higher energy input generally leads to wider clads with reduced height, while lower material supply or insufficient thermal input may result in narrower and more pronounced bead profiles. These trends are consistent with the visual observations of clad morphology across the different runs.

Overall, the cross-sectional analysis confirms that all process conditions produced defect-free clads with acceptable metallurgical bonding and controlled dilution. However, the observed variations in geometric features and symmetry show the importance of parameter optimization in achieving consistent and high-quality clad layers. These geometric differences are further analyzed quantitatively in the following sections.

3.2. Statistical Investigation of Temperature Changes

Table 2. Statistical significance of main effects and two-way interactions for melt pool temperature.

Term	Coefficient	p-Value	Significance
Wire preheating current (WP)	8.46	0.180	Not significant
Deposition speed (DS)	−64.04	0.000	Significant
Power (P)	68.21	0.000	Significant
Wire feed speed (WFS)	−10.96	0.089	Not significant
WP × DS	−11.44	0.142	Not significant
WP × P	−2.31	0.757	Not significant
WP × WFS	−8.56	0.263	Not significant
DS × P	−24.19	0.006	Significant
DS × WFS	13.31	0.092	Not significant
P × WFS	−8.31	0.276	Not significant

presents the statistical significance of the main process parameters and their two-way interactions on melt pool temperature. Based on a significance level of p < 0.05, deposition speed and laser power are identified as the most influential factors affecting the temperature response. Deposition speed exhibits a negative coefficient, indicating that increasing this speed reduces the melt pool temperature. In contrast, laser power shows a positive effect, confirming that higher energy input leads to an increase in temperature. Wire preheating current and wire feed speed are not statistically significant within the investigated range, although the effect of wire feed speed is relatively close to the significance threshold. This suggests that their direct influence on temperature is less pronounced compared with deposition speed and laser power. Among the interaction terms, only the interaction between deposition speed and laser power is statistically significant. The negative coefficient of this term indicates that the combined effect of these two parameters is not purely additive, and that the influence of laser power on temperature depends on the selected deposition speed. The remaining interaction terms (WP × DS, WP × P, WP × WFS, DS × WFS, and P × WFS) are not statistically significant, indicating that their combined effects on temperature are limited within the studied parameter space.

The term “coefficient” in the table refers to the estimated regression coefficient of the RSM model, indicating the direction and relative magnitude of each main effect or interaction term on the response variable.

Overall, the statistical results demonstrate that melt pool temperature is primarily governed by the balance between energy input and process speed, while other parameters play a secondary role under the selected experimental conditions. The developed model shows strong agreement with the experimental data, with a coefficient of determination of R² = 95.69% and an adjusted R² = 90.39%, indicating that the selected parameters effectively explain the variability in melt pool temperature.

The main effects plots presented in Figure 6 illustrate the individual influence of the process parameters on the mean melt pool temperature. Among the investigated parameters, laser power exhibits the strongest influence on temperature. A clear increasing trend is observed, where the melt pool temperature rises significantly with increasing laser power. This behavior is expected, as higher power directly increases the energy input into the system, resulting in higher thermal accumulation within the melt pool. In contrast, deposition speed shows a strong negative effect on temperature. As the deposition speed increases, the melt pool temperature decreases noticeably. This is attributed to the reduced interaction time between the laser beam and the substrate, which limits heat accumulation and leads to lower thermal input per unit length. The curvature observed in the plot suggests a non-linear relationship, with temperature decreasing more rapidly at lower speeds and stabilizing at higher speeds. The effect of wire preheating current is relatively weak compared with deposition speed and power. A slight variation in temperature is observed across the investigated range, with a mild non-linear trend. The temperature initially decreases slightly and then increases at higher preheating levels, indicating that wire preheating has a secondary influence on the thermal behavior of the process. This observation is consistent with the statistical results, where wire preheating current was not identified as a significant factor. Similarly, wire feed speed shows a limited influence on temperature. A slight decreasing trend is observed with increasing wire feed speed, which may be attributed to the increased material input absorbing part of the available thermal energy. However, the variation is relatively small, confirming that wire feed speed has a minor effect on melt pool temperature compared with laser power and deposition speed.

Overall, the main effects plots confirm that melt pool temperature is primarily governed by the balance between energy input (laser power) and deposition speed, while wire preheating current and wire feed speed play a secondary role. These observations are in strong agreement with the statistical analysis presented in Table 2.

3.3. Statistical Investigation of Clad Height

Table 3. Statistical significance of main effects and two-way interactions for clad height.

Term	Coefficient	p-Value	Significance
Wire preheating current (WP)	−3.7	0.747	Not significant
Deposition speed (DS)	−166.6	<0.001	Significant
Power (P)	−25.9	0.040	Significant
Wire feed speed (WFS)	134.3	<0.001	significant
WP × DS	−2.6	0.853	Not significant
WP × P	0.1	0.993	Not significant
WP × WFS	5.1	0.719	Not significant
DS × P	6.4	0.655	Not Significant
DS × WFS	−40.1	0.013	significant
P × WFS	2.6	0.853	Not significant

presents the statistical significance of the main process parameters and their two-way interactions on clad height. Based on a significance level of p < 0.05, deposition speed, laser power, and wire feed speed were found to significantly affect the clad height. Among these factors, deposition speed showed the strongest negative effect, indicating that increasing this speed leads to a reduction in clad height. This behavior can be attributed to the lower energy input per unit length and reduced material accumulation at higher travel speeds. Wire feed speed exhibited a strong positive effect on clad height, confirming that increasing the material feed rate promotes the formation of taller deposits. In contrast, power showed a statistically significant but smaller negative effect, suggesting that higher power levels may increase melt pool spreading and reduce the final bead height under the investigated conditions. Wire preheating current did not have a statistically significant effect on clad height within the selected parameter range. Among the two-way interaction terms, only the interaction between deposition speed and wire feed speed was statistically significant. The negative coefficient of this interaction indicates that the effect of wire feed speed on clad height depends on the selected deposition speed, and that the height increase associated with higher wire feed speed becomes less pronounced at higher deposition speed. The remaining interaction terms were not statistically significant, showing a limited combined effect on clad height within the studied process window. The developed model showed strong agreement with the experimental data, with R² = 96.86% and adjusted R² = 93.00%, showing that the selected parameters explain most of the variability in clad height.

The main effects plots presented in Figure 7 illustrate the individual influence of process parameters on the mean clad height. Among the investigated parameters, wire feed speed exhibits the strongest positive influence on clad height. A clear increasing trend is observed, where higher wire feed speed results in significantly taller clads. This behavior is expected, as increasing the material supply rate leads to greater material accumulation within the melt pool, thereby increasing the deposited layer height. In contrast, deposition speed shows a pronounced negative effect on clad height. As the deposition speed increases, the clad height decreases significantly. This is attributed to the reduced energy input per unit length and shorter interaction time between the laser and substrate, which limits both melting and material deposition. The non-linear curvature observed in the plot suggests that the reduction in height is more significant at lower speeds and tends to stabilize at higher speeds. The effect of laser power on clad height is relatively moderate compared with deposition speed and wire feed speed. A slight decreasing trend is observed with increasing power, indicating that higher energy input promotes melt pool spreading rather than vertical buildup. As a result, the deposited material tends to form wider and flatter clads, leading to a reduction in height. Wire preheating current shows a minimal effect on clad height within the investigated range. The plot indicates only a slight variation, with a mild increase followed by a decrease at higher preheating levels. This confirms that preheating does not significantly influence the clad height compared with the dominant effects of deposition speed and wire feed speed.

3.4. Statistical Investigation of Clad Width

Table 4. Statistical significance of main effects and two-way interactions for clad width.

Term	Coefficient	p-Value	Significance
Wire preheating current (WP)	2	0.892	Not significant
Deposition speed (DS)	−193.3	<0.001	Significant
Power (P)	166.1	<0.001	Significant
Wire feed speed (WFS)	−0.1	0.995	Not significant
WP × DS	−2.9	0.873	Not significant
WP × P	−5.8	0.750	Not significant
WP × WFS	5.9	0.745	Not significant
DS × P	35.2	0.067	Not Significant
DS × WFS	12.6	0.487	Not significant
P × WFS	−18	0.326	Not significant

presents the statistical significance of the main process parameters and their two-way interactions on clad width. Based on a significance level of p < 0.05, deposition speed and power were identified as the only statistically significant main factors affecting clad width. Deposition speed exhibited a strong negative coefficient, indicating that increasing the deposition speed leads to a reduction in clad width. This behavior is associated with the lower energy input per unit length and the shorter interaction time available for melt pool spreading. In contrast, laser power showed a strong positive effect on clad width, confirming that increasing the power promotes greater melting and lateral spreading of the deposited material, which results in wider clads. Wire preheating current and wire feed speed were not statistically significant within the investigated range, indicating that their direct effects on clad width were limited under the selected experimental conditions. None of the two-way interaction terms were statistically significant at the selected confidence level, although the interaction between deposition speed and laser power approached significance with a p-value of 0.067. This suggests that the combined effect of these two parameters may have some influence on clad width, but it was not strong enough to be considered statistically significant within the present experimental domain. The developed model showed strong agreement with the experimental data, with R² = 96.47% and adjusted R² = 92.13%, indicating that the selected factors explain most of the variability in clad width.

The main effects plots presented in Figure 8 illustrate the individual influence of the process parameters on the mean clad width. Among the investigated parameters, deposition speed shows a strong negative influence on clad width. As the deposition speed increases, the clad width decreases markedly. This trend indicates that higher deposition speed reduces the heat input per unit length and shortens the interaction time between the laser beam and the deposited material, thereby limiting lateral melt pool spreading. The curvature of the plot further suggests that the effect is non-linear, with a more pronounced reduction in width at lower deposition speeds. In contrast, laser power exhibits a strong positive effect on clad width. Increasing the power leads to a significant increase in clad width, particularly from the lower to intermediate range of the investigated values. This behavior is expected because higher power enhances melting and promotes broader spreading of the molten material over the substrate surface. At the highest power levels, the trend begins to level off, indicating that the widening effect becomes less pronounced beyond a certain energy input. The effects of wire preheating current and wire feed speed are comparatively small. Wire preheating current shows only a slight variation in clad width, with a weak non-linear trend, confirming that its influence on width is limited within the studied range. Similarly, wire feed speed has a nearly flat effect, indicating that changes in material supply do not substantially alter the lateral dimension of the clad under the selected processing conditions.

Overall, the main effects plots confirm that clad width is primarily governed by the balance between laser power and deposition speed, while wire preheating current and wire feed speed have negligible direct influence.

3.5. Statistical Investigation of Side Angle

Table 5. Statistical significance of main effects and two-way interactions for side angle.

Term	Coefficient	p-Value	Significance
Wire preheating current (WP)	−0.563	0.466	Not significant
Deposition speed (DS)	7.854	<0.001	Significant
Power (P)	3.062	0.001	Significant
Wire feed speed (WFS)	−8.771	<0.001	significant
WP × DS	0.031	0.973	Not significant
WP × P	0.969	0.311	Not significant
WP × WFS	−0.281	0.764	Not significant
DS × P	−0.406	0.665	Not Significant
DS × WFS	1.344	0.167	Not significant
P × WFS	2.406	0.021	significant

presents the statistical significance of the main process parameters and their two-way interactions on side angle. Based on a significance level of p < 0.05, deposition speed, laser power, and wire feed speed were identified as statistically significant main factors. Among these, deposition speed and power exhibited positive coefficients, indicating that increasing either parameter tends to increase the side angle. In contrast, wire feed speed showed a negative coefficient, meaning that increasing the material feed rate reduces the side angle. Wire preheating current did not have a statistically significant effect on side angle within the investigated range. Among the two-way interaction terms, only the interaction between power and wire feed speed was statistically significant. The positive coefficient of this interaction indicates that the combined effect of power and wire feed speed on side angle is not purely additive, and that the influence of power depends on the selected wire feed speed. The remaining interaction terms were not statistically significant, indicating that their combined effects on side angle were limited under the selected experimental conditions. The developed model showed good agreement with the experimental data, with R² = 95.88% and adjusted R² = 90.82%, indicating that the selected parameters explain most of the observed variability in side angle.

The main effects plots presented in Figure 9 illustrate the individual influence of the process parameters on the mean side angle of the clad. Among the investigated parameters, wire feed speed shows the strongest influence on side angle, with a clear negative trend. As the wire feed speed increases, the side angle decreases markedly. This behavior indicates that higher material supply promotes a broader and less steep bead profile, thereby reducing the side wall angle. The effect is pronounced over the entire investigated range, confirming the strong role of wire feed speed in determining the final clad geometry. In contrast, deposition speed exhibits a strong positive effect on side angle. Increasing the deposition speed leads to a noticeable increase in side angle, indicating the formation of steeper clad flanks. This can be attributed to the reduced heat input per unit length at higher travel speeds, which limits lateral spreading and promotes a more compact bead profile. The trend also shows a non-linear behavior, with the side angle increasing rapidly at lower deposition speeds and approaching a plateau at higher values. Laser power also has a statistically significant positive effect on side angle, although its influence is weaker than that of deposition speed and wire feed speed. The plot shows that increasing power initially increases the side angle, followed by a slight reduction at the highest power levels. This trend suggests that moderate increases in power enhance clad buildup, while excessive power promotes melt pool spreading and slightly reduces the steepness of the side walls. The effect of wire preheating is relatively small and statistically insignificant. The plot shows only a mild curved trend, with limited variation in side angle across the investigated range. This confirms that wire preheating has a secondary influence on this response compared with the dominant effects of deposition speed, laser power, and wire feed speed.

Overall, the results clarify the respective roles of the main process variables in wire laser cladding of bronze on AISI 304 stainless steel. Laser power and deposition speed primarily determined the thermal response and strongly influenced clad width, whereas wire feed speed mainly affected clad height. The side angle reflected the combined balance between thermal input and material supply. Within the investigated range, wire preheating did not show a statistically significant effect. These findings provide the basis for the main conclusions summarized in the following section.

It is important to mention that the dilution ratio calculated from the cross-sectional images was below 2% for all investigated conditions, with only minor variation between samples; therefore, it was not considered as a separate response variable.

4. Conclusions

In this study, wire laser cladding of CuAl9Ni5Fe3Mn2 bronze on AISI 304 stainless steel was investigated within a process window of 5–65 A wire preheating current, 3–15 mm/s deposition speed, 625–1125 W laser power, and 4.5–18.5 mm/s wire feed speed. The effects of these parameters on melt pool temperature and clad geometry were analyzed using response surface methodology. The main conclusions are as follows:

• Continuous and defect-free bronze clads with good metallurgical bonding and limited dilution below 2% were obtained within the investigated parameter range. However, the clad geometry varied significantly depending on the balance between heat input and material supply.
• Melt pool temperature was primarily controlled by laser power and deposition speed, with a significant interaction between these parameters. Based on the RSM model, laser power increased temperature significantly (regression coefficient = +68.21, p < 0.001), while deposition speed reduced it (regression coefficient = −64.04, p < 0.001). The model showed high accuracy with R² = 95.69%.
• Clad height increased with wire feed speed and decreased with deposition speed, indicating strong dependence on material supply and energy input per unit length. Based on the model, wire feed speed increased height (regression coefficient = +134.3, p < 0.001), whereas deposition speed decreased it (regression coefficient = −166.6, p < 0.001).
• Clad width increased with laser power and decreased with deposition speed, confirming that lateral spreading is mainly governed by thermal conditions.
• Side angle increased with deposition speed and laser power, while it decreased with increasing wire feed speed, reflecting the balance between vertical buildup and melt pool spreading.
• Wire preheating showed no statistically significant influence on temperature or clad geometry within the investigated range.
• High-quality and uniform clads were mainly obtained when laser power, deposition speed, and wire feed speed were properly balanced, particularly within 750–1125 W, 3–12 mm/s, and 8–18.5 mm/s, respectively.