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Article

Preparation and Tribology of Textured Ti-6Al-4V with Thermal Oxide Coating

by
Xiaoyi Wang
1,2,
Zhibiao Xu
1,2,*,
Haowen Lu
2,
Yue Tan
3,
Xing Xu
1 and
Hao Wu
4,*
1
College of Intelligent Manufacturing, Guangzhou Maritime University, Guangzhou 510725, China
2
School of Rail Transportation, Wuyi University, Jiangmen 529020, China
3
Guangdong Institute of Special Equipment Inspection and Research, Foshan 510655, China
4
Guangdong Key Laboratory of Materials and Equipment in Harsh Marine Environment, School of Ocean Engineering, Guangzhou Maritime University, Guangzhou 510725, China
*
Authors to whom correspondence should be addressed.
Coatings 2025, 15(3), 258; https://doi.org/10.3390/coatings15030258
Submission received: 3 February 2025 / Revised: 15 February 2025 / Accepted: 20 February 2025 / Published: 21 February 2025
(This article belongs to the Special Issue Advances in Surface Coatings for Wear and Corrosion Protection)
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Versions Notes

Abstract

:
This study investigates the tribological properties of Ti-6Al-4V alloy treated with single laser texturing, single thermal oxidation, and laser texturing combined with thermal oxidation in a PAO6 oil environment. The surface morphology, cross-sectional morphology, surface chemical composition, microhardness, wettability, and wear surface morphology were analyzed using a three-dimensional profiler, scanning electron microscope, electron spectrometer, X-ray diffractometer, micro-Vickers hardness tester, and optical contact angle measuring instrument. The results indicate that combining laser texturing with thermal oxidation treatment enhances groove edge hardness to approximately 1932 HV0.2, due to the synergistic effects of laser-induced heat-affected zones and the formation of high-hardness rutile phase TiO2. Simultaneously, the treatment effectively enhances the wettability of PAO6 oil on the surface. Furthermore, the composite-treated surface combines the oil reservoir and debris-trapping capabilities of a single laser-textured surface with the excellent load-bearing capacity of a single thermally oxidized surface. This enhancement improves the durability and reliability of the groove-type texture, leading to reduced material loss and a diminished wear rate, and significantly improving the surface wear resistance of Ti-6Al-4V alloy.

1. Introduction

Titanium alloys demonstrate exceptional properties including low density, high specific strength, excellent high-temperature resistance, and corrosion resistance [1,2,3,4], positioning them as an ideal choice for applications in marine vessels [5], aerospace [6], biomedical [7], and other fields. However, their broad industrial application is impeded by challenges such as low load-bearing capacity and inadequate wear resistance [8,9,10].
Currently, surface treatment techniques aimed at enhancing the wear resistance of titanium alloys include laser texturing [11,12], thermal oxidation [13,14], ion implantation [15], and micro-arc oxidation [16]. Laser texturing (LT) technology is a surface ‘reshaping’ method that utilizes the thermal effect of a high-energy laser beam to produce tiny grooves, pits, and other specific texture shapes on the surface of the material. This approach is commonly used across various fields due to its economic efficiency, simplicity, and environmental friendliness. Ozan et al. [17] tested various LT parameters (scan speed, frequency, hatch spacing, pulse width, direction) on Ti-6Al-7Nb, revealing significant effects on surface roughness and wettability. Shivakoti et al. [18] applied textures with different shapes using laser on Ti-6Al-4V, also observing notable wettability changes. Li et al. [19], through optimized parameters, designed three bionic textures on Ti-6Al-4V using femtosecond laser processing, effectively reducing and trapping wear particles, thereby enhancing wear resistance. Although LT enhances the wear resistance of titanium alloy surfaces, excessive damage to the textured morphology can severely diminish its anti-wear capabilities. Consequently, enhancing the durability and reliability of the surface texture morphology in titanium alloys is crucial.
Wu et al. [20] combined the advantages of LT technology and micro-arc oxidation technology on Ti-6AL-4V alloy to prepare a gradient anti-wear coating, significantly enhancing the wear resistance of the titanium alloy. Xue et al. [21], aiming to improve the tribological properties and suppress friction noise of Ti-6AL-4V alloy, fabricated a composite self-lubricating surface by combining groove-type LT with Sn-Ag-Cu coating. They found that the synergistic effect of groove-type LT and Sn-Ag-Cu coating reduced the high contact stress at the groove edges, inhibiting adhesive wear and friction noise. Zhang et al. [22] deposited a 50 nm thick MXene nanocoating on the groove-textured pure Ti surface, reducing its friction coefficient from 0.57 to 0.17, thereby greatly mitigating wear on the Ti substrate. Lei et al. [2], on the other hand, employed a combination of LT and double-glow plasma chromium infiltration to similarly enhance the wear resistance of Ti-6AL-4V alloy. The aforementioned research demonstrates that the integration of coatings with LT can achieve synergistic benefits, positively impacting the tribological and wear properties of titanium alloys.
Thermal oxidation (TO) is a surface ‘modification’ technique that utilizes high-temperature oxygen diffusion to form an oxide layer on metal surfaces. The resulting oxide exhibits high hardness and wear resistance, significantly enhancing the wear resistance of titanium alloys [23]. Additionally, TO is a straightforward, environmentally friendly, and cost-effective surface modification technique [24]. Furthermore, because TO can effectively improve the wettability of titanium alloy surfaces [25] and does not impose specific requirements on LT shapes, combining these methods may be more advantageous for forming lubricant films during sliding friction processes, thereby reducing frictional wear.
Presently, there is limited research on the combination of LT and TO treatment for the surface of Ti-6Al-4V alloy. Therefore, this investigation employs laser texturing for surface reshaping in conjunction with thermal oxidation for surface modification (LT + TO) technology, fully exploiting the advantages of both methods to achieve synergistic control over the formability of Ti-6Al-4V alloy surfaces, thereby effectively enhancing the durability and reliability of the textured morphology. Initially, LT technology was employed to create grooved textures on the surface of Ti-6Al-4V alloy. Subsequently, high-quality oxide films were produced using TO based on this foundation. Finally, the characteristics of the Ti-6Al-4V alloy subjected to LT and TO were examined, along with its friction and wear behavior in a PAO6 oil environment. This was followed by a detailed analysis of the wear mechanisms associated with the surface treated through this combined approach.

2. Materials and Methods

This investigation employed Ti-6Al-4V alloy samples measuring 40 × 20 × 5 mm³ as substrates, with their chemical composition and content detailed in Table 1. Prior to LT, the alloy surfaces were sequentially polished using sandpapers with grit sizes of 400, 800, 1000, 1200, 1500, and 2000, followed by fine polishing with 1.5 µm and 0.5 µm diamond polishing pastes, and 0.04 µm silica suspension to achieve a smooth, scratch-free finish. Subsequently, the samples were placed in ethanol solution and cleaned via ultrasonication for 20 min to remove residual contaminants, air-dried at room temperature, and stored in a constant temperature chamber.
Initially, a nanosecond laser marking system (LSF20DH, Wuhan Huagong Laser Engineering Co., Ltd., Wuhan, China) was employed to create groove-type microstructures on Ti-6Al-4V alloy surfaces. Optimal laser parameters were determined via an orthogonal experiment: wavelength of 1064 nm, laser power of 10 W, pulse frequency of 150 kHz, scanning speed of 1000 mm/s, 40 scanning passes, laser spot diameter of 50 µm, and line spacing of 100 µm. The machining principle is depicted in Figure 1a. Subsequently, the samples were transferred to a box resistance furnace (BF1200-30, Kunshan Aikexun Machinery Co., Ltd., Kunshan, China), heated at a rate of 10 °C/min to 700 °C, held for 5 h, and then allowed to cool naturally to ambient temperature within the furnace to obtain thermally oxidized samples. Figure 1b presents a schematic diagram illustrating the principles of TO processing, which generally comprises five stages [26]: (1) oxygen absorption, (2) oxygen dissolution, (3) formation of oxide film, (4) growth of oxide layer, (5) development of thick oxide layer.
Utilizing a three-dimensional optical profiler (ContourX-200, Bruker, Ettlingen, Germany), the three-dimensional profiles of various sample surfaces were examined. The surface and cross-sectional structures of the samples were analyzed using scanning electron microscopy (SEM, ZEISS SIGMA 300, Jena, Germany), while energy-dispersive spectroscopy (EDS) was employed to evaluate the elemental composition of the surface. Phase analysis of the samples was conducted using Rigaku SmartLab XRD (Tokyo, Japan) with a scan rate set at 5°/min, a step size of 0.02°, and a scan range from 20 to 80° (in 2θ). Surface hardness was measured with a micro-Vickers hardness tester (HVT-100A, Jinan Huayin Test Instrument Co., Ltd., Jinan, China), applying a load of 1.96 N (HV0.2) for 15 s. The wettability of PAO6 oil on different sample surfaces at room temperature was assessed using an optical contact angle measurement instrument (CA100, Guangdong Beidou Precision Instrument Co., Ltd., Dongguan, China). Each measurement involved a droplet volume of 3 µL, and the data were automatically recorded by the device. To ensure the consistency and reliability of the data, each sample surface underwent microscopic hardness and contact angle testing more than three times.
A reciprocating motion friction test with a ball-on-flat contact configuration was conducted using the friction and wear tester (UMT-TriboLab, Bruker). The friction pair consisted of a 6 mm diameter Si3N4 friction ball and specimens prepared from Ti-6Al-4V alloy subjected to various surface treatment techniques as the counter-specimen. The friction coefficients and their corresponding curves were automatically recorded by the testing equipment, and the friction and wear test parameters are presented in Table 2. To ensure the reliability and consistency of friction test data, at least three parallel tests are conducted for each wear condition. The three-dimensional morphology of surface wear on different specimens was analyzed using a three-dimensional measurement microscope (Micro 1000, Suzhou Ruifei Optoelectronics Technology Co., Ltd., Suzhou, China). Six two-dimensional profile lines perpendicular to the wear region were extracted to determine the cross-sectional area by integrating the enclosed area within the boundaries of the wear region’s two-dimensional cross-section. To ensure consistency and reliability in measurements, each cross-section was measured three times. The wear volume and wear rate were calculated according to the formulas V = AL [27] and W = V/(F × S) [20], respectively. Herein, V represents the wear volume, A denotes the average cross-sectional area of surface wear marks, L signifies the sliding distance (for a single reciprocation in the context of this test), W indicates the wear rate, F stands for the normal load, and S signifies the total sliding distance.

3. Results and Discussion

3.1. Surface Morphology

From Figure 2(a1–a3), the LT sample surface exhibits parallel and uniformly distributed grooves and stripes upon laser irradiation, with depths of approximately 124 µm and widths of approximately 35 µm. The grooves exhibit an inverted cone shape, surrounded by particulate protrusions of the recast layer formed by substrate melting and splashing due to laser heating. Accumulation of most splashed molten material on both groove sides results in a height buildup of approximately 17 µm, thereby increasing surface roughness [28]. Figure 2(b1–b3) reveal that the TO sample surface uniformly grows a layer of scales and granular protrusions, completely covered by an oxide layer and diffusion layer, with a surface oxide film thickness of approximately 8 µm. Figure 2(c1–c3) demonstrates that the surface of the LT + TO sample is covered by composite particulate protrusions consisting of splashes from LT and a layer of TO-derived scale-like granular protrusions. Compared to the LT sample, the groove width is slightly reduced, with groove depths of about 66 µm, and the inverted cone-shaped bottoms are partially filled with oxides.

3.2. Surface Chemical Composition

Figure 3 depicts EDS analysis of different sample surfaces, while XRD analysis results are shown in Figure 4. Compared to the original sample (Ti-6Al-4V alloy sample with surface polishing only) surface, the LT sample shows a significant decrease in Ti elemental content and a marked increase in O elemental content. Combined with XRD analysis, it is evident that the LT sample is predominantly composed of α-Ti as the primary phase, with β-Ti and Ti2O3 as secondary phases. During the LT process of Ti-6Al-4V alloy surfaces, interaction with oxygen in the surrounding environment results in the formation of a small amount of Ti2O3, thereby causing a reduction in surface Ti elemental content and an increase in O elemental content. In comparison to the LT sample, both the TO and LT + TO samples show a notable decrease in Ti elemental content on their surfaces, along with significant increases in Al and O elemental content. According to XRD analysis, the primary phase on the surfaces of TO and LT + TO samples is rutile TiO2, with anatase TiO2, Al2O3, and Ti3O as secondary phases. Due to the higher hardness of rutile TiO2 [29], the surfaces of TO and LT + TO samples exhibit increased hardness (Figure 5). Additionally, it is noteworthy that, compared to the TO sample, the LT and LT + TO samples show a significant increase in C elemental content on their surfaces. This is attributed to organic reactions occurring due to temperature variations and the influence of micro-nanostructures during laser surface texturing in atmospheric environments, leading to the adsorption of carbon elements and the formation of a small amount of carbon-containing compounds [30].

3.3. Surface Microhardness

Figure 5 depicts the microhardness of Ti-6Al-4V alloy samples in their original state and after treatment with different surface technologies. For the original and TO samples, four hardness test points were randomly selected on the surface. In contrast, for the LT and LT + TO samples, hardness testing commenced at the groove edge, with four hardness test points taken at intervals of 25 µm along the direction away from the grooves. Noticeable differences in surface hardness were observed after different surface treatments. The original and TO sample surfaces exhibited uniform hardness, with a distinct increase in hardness evident after single TO treatment. Conversely, the hardness of LT and LT + TO samples decreased gradually away from the groove edge, with the LT sample hardness reverting to the original surface hardness more rapidly than the LT + TO sample reverted to the hardness after single TO treatment. This suggests that the hardness near the groove edge is significantly influenced by the laser thermal affected zone and TO technology.

3.4. Surface Wettability

Surface wettability describes a liquid’s ability to either spread or bond with a solid surface, which is affected by factors including surface chemistry, free energy, and morphological characteristics. Typically, the contact angle (CA) is used to characterize this property, defined as the angle formed by the solid-liquid interface and the tangent at the edge of the liquid droplet [31]. Figure 6a depicts the dynamic variation in the contact angle of PAO6 oil on different samples over 5 s. Within the initial second, compared to the original sample, the contact angle of PAO6 oil decreases more rapidly on the surfaces of the other three samples, indicating enhanced adsorption and spreading tendencies on the surfaces of the samples after surface treatment. Subsequently, over the next 4 s, the contact angle of all samples showed a tendency to decrease slowly and become stable. The average contact angle of PAO6 oil on the surfaces of different samples after 5 s is depicted in Figure 6b. It is evident that PAO6 oil droplets exhibit varying degrees of wetting on different sample surfaces. Compared to the original sample, surfaces treated with either single or combined methods show a significant reduction in the contact angle of PAO6 oil, thereby improving their surface wettability. This phenomenon arises from the LT process, which induces deformation on the surface of the Ti-6Al-4V alloy, resulting in increased surface roughness due to molten material accumulation. Concurrently, the contact area between the surface and the droplet is diminished, modifying the contact angle. TO treatment results in the formation of metal oxides with oleophilic properties and high surface energy on the surface. The unique structure resulting from the combination of LT and TO treatment enables the samples to possess both stable oil retention capabilities from LT and excellent spreading properties from TO, facilitating the formation of a lubricating oil film during sliding friction.

3.5. Friction and Wear

3.5.1. Tribological Properties

Figure 7a,b illustrate the friction coefficient variation curves and average friction coefficients of different samples under varying normal loads in PAO6 oil environment. From Figure 7a, it is evident that the friction coefficient curve exhibits two distinct stages: the running-in phase and the steady state. The running-in phase is more pronounced for the LT sample compared to the TO and LT + TO samples. As friction time increases, the friction coefficients of LT and TO samples stabilize, whereas the LT + TO sample initially shows a gradual increase followed by a slight decrease, converging towards the friction coefficient of the LT sample. Combining this with the average friction coefficient in Figure 7b, it is observed that the TO sample exhibits a lower average friction coefficient compared to the LT sample, potentially due to factors such as higher surface roughness of the LT sample and lower surface hardness (Figure 5). Additionally, it is noteworthy that the friction coefficient of the LT + TO sample is lower than that of the LT sample, attributed to the macroscopic texturing reducing the actual contact area between the counter-sphere and the sample, thereby decreasing friction resistance [20]. The oxide film enhances surface hardness at the microscopic level, thereby improving load-bearing capacity [27]. The combined effect of these factors contributes positively to reducing the friction coefficient to some extent.
Figure 7c,d display the wear volumes and rates for three distinct samples subjected to different loads. As the normal load gradually increases, the wear volume of all samples exhibits an increasing trend. However, in terms of wear rate, there is a differentiated variation trend with the increase in normal load. Specifically, the wear rate of LT samples and LT + TO samples increases with the increase in load, while the wear rate of TO samples decreases with the increase in load. This phenomenon is attributed to the oxide film formed on the surface of TO samples under higher loads, which can effectively disperse the stress concentration in the contact area, making the compressive strength and hardness characteristics of the oxide film more prominent, and thus enhancing its ability to withstand greater friction without breaking. This change reduces the frequency of direct contact between the matrix metal surface and the counterpart, thereby further strengthening the protective effect of the oxide film. Therefore, under higher loads, the wear rate of TO samples exhibits a decreasing trend compared to that under lower loads. Furthermore, it is noteworthy that the LT + TO sample exhibits the lowest wear volume and wear rate compared to other samples. At a normal load of 15 N, compared to the LT and TO samples, the LT + TO sample shows reductions in wear volume by 8.33% and 26.19%, and decreases in wear rate by 8.24% and 26.27%, respectively. At a normal load of 20 N, relative to the LT and TO samples, the LT + TO sample demonstrates reductions in wear volume by 13.76% and 16.58% and decreases in wear rate by 13.67% and 16.63%. The reduction in wear volume and reduction in wear rate indicate that the LT and TO composite treatment of Ti-6Al-4V alloy enhances the durability and reliability of its textured morphology.

3.5.2. Wear Surface Morphology

Figure 8 presents SEM images showcasing the worn surfaces of three samples alongside Si3N4 balls under different normal loads in a PAO6 oil environment. The EDS results from selected points on these worn surfaces are detailed in Table 3. Figure 8(a1,a2) illustrates the wear morphology of the LT sample’s surface. It reveals that the molten deposits on the groove flanks of the LT sample have been abraded flat, with the grooves completely filled with abrasive debris. Additionally, the worn surface exhibits numerous furrows, a small number of spalling pits, and microcracks, which become more pronounced with increasing applied normal loads. EDS analysis (points A, B, C, and D in Table 3) identified trace amounts of Si elements, indicating material transfer from the Si3N4 balls and implying an adhesive wear mechanism. This analysis suggests that the wear mechanisms affecting the LT sample encompass abrasive wear, adhesive wear, and fatigue wear.
The wear morphology of the TO sample’s surface is presented in Figure 8(b1,b2). Due to the presence of a high-hardness oxide film coating, abrasive wear phenomena are absent on the TO sample surface. The worn edges exhibit a stepped division from the unworn area, resembling cohesive spalling, with the worn surface displaying plastic deformation. As the applied load increases, plastic deformation becomes more pronounced. EDS analysis (points E, F, G, and H in Table 3) also detected trace amounts of Si elements on the worn surface, confirming material transfer. Analysis reveals that the primary wear mechanisms on the TO sample surface are adhesive wear and fatigue wear.
Figure 8(c1,c2) illustrates the wear morphology of the LT + TO sample’s surface. Under cyclic frictional loading, the width of the wear track widens with increasing applied load. The primary wear regions on the sample surface are the accumulation of molten material and the hard oxide film covering it. In areas without accumulation of molten material, the surface oxide film experiences only minor wear. Furthermore, the worn surface exhibits microcracking and spalling phenomena. EDS analysis (points I, J, K, and L in Table 3) similarly identified a significant presence of O elements and trace amounts of Si elements on the worn surface, confirming the presence of the oxide film coating and material transfer. Analysis indicates that the primary wear mechanisms on the LT + TO sample surface are adhesive wear and fatigue wear. Compared to the LT sample, the LT + TO sample exhibits reduced capture of wear debris within its grooves, potentially facilitating prolonged and continuous lubricant release. This reduced debris capture in the LT + TO sample is attributed to two primary factors: firstly, the larger, block-like wear debris formed by the detachment of oxide films on the LT + TO sample’s surface is less easily trapped; secondly, as friction continues, some of the captured block-like debris can be released due to the fluid dynamic effects of the lubricant. Furthermore, a clear comparison between the two samples reveals that the groove texture of the LT + TO sample remains intact under both load conditions. The integration of LT and TO thus significantly enhances the durability and reliability of the Ti-6Al-4V alloy’s surface texture.
Figure 9 illustrates the three-dimensional surface wear morphology and cross section profile curves of different samples under 20 N normal load. It is evident that, compared to the LT and TO samples, the LT + TO sample exhibits the narrowest and shallowest wear track width on its surface. The wear track of the LT sample appears as a circular-bottom ‘U’ shape, while those of the TO and LT + TO samples appear as flat-bottom ‘凵’ shapes. During the friction process, the initial area to experience wear on the LT and LT + TO samples is the splashed molten material on the groove sides, followed by the exposed surface. The molten material on the sides of the grooves in the LT sample wears more rapidly due to a smaller contact area with the counterpart sphere and higher stress. In contrast, the LT + TO sample, which develops a hard oxide film following TO treatment, increases surface load capacity, thereby decreasing the wear rate of the molten material at the groove edges. Additionally, the contact area of the TO sample with the counterpart sphere is relatively large, and stress is relatively dispersed. Compared to the TO sample, the grooves on the surface of the LT + TO sample can store lubricating oil and capture wear debris, effectively reducing wear. Furthermore, the combination of LT with TO treatment results in a unique structure that combines LT’s ability to store lubricating oil and capture wear debris with TO’s exceptional load-bearing capacity.

3.5.3. Wear Mechanisms

Figure 10 illustrates the schematic diagram depicting the friction and wear mechanisms of different samples in PAO6 oil environment. Following LT, the Ti-6Al-4V alloy surface undergoes effects from the heat-affected zone, leading to the formation of partially hardened regions. Concurrently, the grooved texture structure on the surface reduces the contact area during frictional processes, inducing a scenario of alternating stress distribution in the contact zone with varying positions of stress concentration points as friction progresses. Additionally, the grooves effectively capture abrasive debris, thereby mitigating abrasive wear [32]. Furthermore, the grooved texture enhances fluid dynamic effects, thereby generating additional load-bearing capacity. Over time, these grooves serve as micro-oil channels during continuous friction, ensuring a sustained release of lubricating oil for secondary lubrication [28,33]. Following TO processing, a hard oxide film forms on the Ti-6Al-4V alloy surface, significantly improving surface hardness and enhancing load-bearing capacity. Moreover, it enhances surface wettability, facilitating rapid spreading and formation of a lubricating oil film [34]. The integration of LT for ‘reshaping’ and composite TO for ‘modification’ leverages the benefits of both techniques. Consequently, the Ti-6Al-4V alloy surface features grooves for lubricant storage and abrasive debris capture, alongside laser-hardened regions in specific areas. This approach also forms a high-quality oxide film coating to enhance the durability and reliability of surface texture morphology. Compared to single LT or TO treatments, the combined LT and TO treatment establish multiple protective mechanisms on the substrate, thereby further enhancing the tribological properties of Ti-6Al-4V alloy surfaces in PAO6 oil environment.

4. Conclusions

This study integrates LT with TO techniques to fabricate groove-type textures with high-quality oxide film coatings. Comparative analysis of surface morphology, chemical composition, microhardness, wettability, and frictional performance yields the following conclusions:
(1)
The LT + TO samples, affected by the combined influences of laser-induced heat affected zone and TO resulting in the formation of high-hardness rutile phase TiO2, exhibited significantly higher groove edge hardness (1932 HV0.2) compared to the LT samples (720 HV0.2). Relative to the original samples, all three surface treatment techniques effectively reduced the contact angle of PAO6 oil, enhancing wettability for the formation of lubricating oil films during sliding friction.
(2)
Compared to LT and TO samples, the LT + TO samples demonstrate reduced wear volume and wear rate. At a normal load of 15 N, the wear volume decreased by 8.33% and 26.19%, with corresponding decreases in wear rate by 8.24% and 26.27%. Under a normal load of 20 N, the wear volume decreased by 13.76% and 16.58%, and the wear rate decreased by 13.67% and 16.63%. The wear mechanisms observed were abrasive wear, adhesive wear, and fatigue wear for LT samples; adhesive wear and fatigue wear for TO samples; and adhesive wear and fatigue wear for LT + TO samples.
(3)
The surface of the LT + TO samples after processing combines the oil storage capability and debris capturing ability of the LT samples with the excellent load-bearing capacity of the TO samples. Furthermore, the composite treatment also effectively enhances the durability and reliability of the groove-type texture morphology, thereby significantly improving the tribological properties of Ti-6Al-4V alloy.

Author Contributions

Conceptualization: X.W., Z.X., H.L., Y.T. and X.X.; data curation: X.W. and Z.X.; formal analysis: X.W., Z.X. and H.W.; funding acquisition: Z.X. and Y.T.; investigation: X.W. and H.W.; methodology: X.W., H.L., Y.T. and X.X.; project administration: Z.X.; supervision: Z.X.; validation: Z.X. and H.L.; visualization: X.W. and H.L.; writing—original draft: X.W.; writing—review and editing: Z.X., H.W. and X.X. All authors have read and agreed to the published version of the manuscript.

Funding

The work was supported by National Natural Science Foundation of China (No. 52105202); Industry-Academia Collaboration for Talent Cultivation Project of the Ministry of Education (No. 231106429201145); Guangdong Provincial Administration for Market Regulation Funds of Science and Technology (No. 2022ZT01).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Schematic diagram of principle (a) laser processing, (b) thermal oxidation processing.
Figure 1. Schematic diagram of principle (a) laser processing, (b) thermal oxidation processing.
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Figure 2. Surface 3D profiles and SEM of different samples, as well as SEM of cross sections: (a) LT sample, (b) TO sample, (c) LT + TO sample.
Figure 2. Surface 3D profiles and SEM of different samples, as well as SEM of cross sections: (a) LT sample, (b) TO sample, (c) LT + TO sample.
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Figure 3. Surface EDS of different samples: (a) LT sample, (b) TO sample, (c) LT + TO sample.
Figure 3. Surface EDS of different samples: (a) LT sample, (b) TO sample, (c) LT + TO sample.
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Figure 4. XRD analysis of different sample surfaces.
Figure 4. XRD analysis of different sample surfaces.
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Figure 5. Surface microhardness of different samples.
Figure 5. Surface microhardness of different samples.
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Figure 6. Contact angle of PAO6 oil on different sample surfaces: (a) dynamic contact angle variation curve within 5 s, (b) average contact angle after 5 s.
Figure 6. Contact angle of PAO6 oil on different sample surfaces: (a) dynamic contact angle variation curve within 5 s, (b) average contact angle after 5 s.
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Figure 7. Friction coefficient variation curves (a), average friction coefficients (b), wear volumes (c), and wear rates (d) of different samples under varying normal loads in PAO6 oil environment.
Figure 7. Friction coefficient variation curves (a), average friction coefficients (b), wear volumes (c), and wear rates (d) of different samples under varying normal loads in PAO6 oil environment.
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Figure 8. SEM of wear surfaces of different samples under varying normal loads in PAO6 oil environment: (a) LT sample, (b) TO sample, (c) LT + TO sample.
Figure 8. SEM of wear surfaces of different samples under varying normal loads in PAO6 oil environment: (a) LT sample, (b) TO sample, (c) LT + TO sample.
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Figure 9. Wear 3D profiles and section profile curves of different samples under 20 N normal load: (a–c) wear 3D profiles, (d) section profile curves.
Figure 9. Wear 3D profiles and section profile curves of different samples under 20 N normal load: (a–c) wear 3D profiles, (d) section profile curves.
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Figure 10. Schematic diagram of friction and wear mechanisms of different samples under PAO6 oil environment.
Figure 10. Schematic diagram of friction and wear mechanisms of different samples under PAO6 oil environment.
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Table 1. Chemical composition of the Ti-6Al-4V alloy (wt%).
Table 1. Chemical composition of the Ti-6Al-4V alloy (wt%).
ElementAlVFeCNHOTi
%6.053.900.150.020.0060.0040.12Bal
Table 2. Friction and wear test parameters.
Table 2. Friction and wear test parameters.
Lubrication ConditionNormal
Constant Load (Fn)		Constant
Traverse Speed (v)		Sliding
Distance (d)		Friction Test Time (t)Test
Temperature (T)
PAO6 oil
lubrication		15 N, 20 N10 mm/s2.5 mm900 s20~25 °C
Table 3. Elemental contents of Ti, Al, V, O, and Si at the corresponding regional points in Figure 8.
Table 3. Elemental contents of Ti, Al, V, O, and Si at the corresponding regional points in Figure 8.
Elment
(wt%)		Corresponding Area Points in Figure 8
ABCDEFGHIJKL
Ti84.4984.0483.8485.8957.9864.2669.8353.7458.9761.5057.6765.07
Al4.555.004.634.792.523.333.692.113.373.213.243.29
V3.693.875.042.612.230.650.885.301.731.243.900.67
O7.226.876.436.5737.2331.6925.4938.5035.8234.0435.0930.89
Si0.060.230.060.140.030.070.110.360.120.010.090.07
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MDPI and ACS Style

Wang, X.; Xu, Z.; Lu, H.; Tan, Y.; Xu, X.; Wu, H. Preparation and Tribology of Textured Ti-6Al-4V with Thermal Oxide Coating. Coatings 2025, 15, 258. https://doi.org/10.3390/coatings15030258

AMA Style

Wang X, Xu Z, Lu H, Tan Y, Xu X, Wu H. Preparation and Tribology of Textured Ti-6Al-4V with Thermal Oxide Coating. Coatings. 2025; 15(3):258. https://doi.org/10.3390/coatings15030258

Chicago/Turabian Style

Wang, Xiaoyi, Zhibiao Xu, Haowen Lu, Yue Tan, Xing Xu, and Hao Wu. 2025. "Preparation and Tribology of Textured Ti-6Al-4V with Thermal Oxide Coating" Coatings 15, no. 3: 258. https://doi.org/10.3390/coatings15030258

APA Style

Wang, X., Xu, Z., Lu, H., Tan, Y., Xu, X., & Wu, H. (2025). Preparation and Tribology of Textured Ti-6Al-4V with Thermal Oxide Coating. Coatings, 15(3), 258. https://doi.org/10.3390/coatings15030258

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