Search Results (35)

In this study, a sustainable advanced manufacturing technology was developed using a holistic approach for finishing heat-treated 42CrMo4 steel cylindrical parts. The proposed technology is based on a hybrid combined process (HCP) involving cool-assisted dry hard turning and subsequent cool-assisted dry diamond burnishing (DB). A cold-air cooling (without lubrication) condition was achieved using a special device with a cold-air nozzle based on the principle of vortex tubes. The study was conducted in two stages. In the first stage, only the hard turning process was investigated using variance analysis to determine the significant governing factors (feed rate and cutting insert radius). The second stage involved studying and optimising the HCP. This approach incorporated the two significant turning process factors, along with three additional DB process factors: the radius of the diamond insert, burnishing force and feed rate. The selected objective functions were the average roughness, skewness, kurtosis, surface microhardness, residual surface axial stress and fatigue limit. The fatigue limit was determined using the accelerated Locati method. Mathematical models of the objective functions were obtained using experiments and regression analyses. Using multi-objective optimisation, the HCP was optimised based on two criteria: (1) maximum wear resistance under boundary lubrication conditions and (2) maximum fatigue limit. The optimisation tasks were solved by searching for the Pareto optimal solution approach using QStatLab and the NSGA II algorithm. The compromise optimal values of the governing factors, maximising the fatigue limit (690 MPa), are as follows: feed rate in turning and DB of 0.05 mm/rev, radius of the cutting insert of 0.8 mm, diamond insert radius of 2 mm, and burnishing force of 50 N. Experimental verification showed a good agreement with the optimised solutions for surface integrity and fatigue limit characteristics. Full article

CuZn39Pb3 leaded brass is one of the most widely used alloys in machining. Despite its good machinability, there is a lack of information in the literature on the effects of surface cold working on the surface microhardness, microhardness profile, introduced residual stresses, microstructure, and the operating behaviour of machined components. This article reveals the capabilities of conventional diamond burnishing (DB) (implemented under flood-lubrication conditions) to improve the surface integrity and high- and mega-cycle fatigue strength of CuZn39Pb3 cylindrical components such as axles and shafts. The results show that both the smoothing and hardening DB processes achieve mirror-like surfaces, introduce significant residual compressive stresses at depths greater than 0.5 mm, and significantly increase the fatigue strength in the high- and mega-cycle regions compared to the reference condition (turned and polished specimens). However, the surface microhardness is weakly affected by the degree of surface cold working. Given the almost identical microhardness profiles and the equivalent distribution in depth of the introduced residual stresses by the two DB processes, the possible reason for the more pronounced effect of the hardening process on the fatigue strength lies in the thicker affected layer and the reduced negative skewness introduced by this process. Full article

This article presents a new combined post-processing concept to improve the quality of laser powder bed fusion (LPBF) of 17-4PH stainless steel (SS) cylindrical parts fabricated from N₂-atomised LaserForm 17-4PH (B) powder. The concept is based on consecutive heat treatment procedures and diamond burnishing (DB) processes. A two-stage study was conducted. The first stage was an LPBF process experiment. The following combination of LPBF parameter values was selected after optimisation: a laser power of $\mathrm{P}=150 \mathrm{W}$, laser scanning speed of v = 1200 mm/s, and layer thickness of $\mathrm{t}=40 \mathsf{\mu }\mathrm{m}$. In the second stage, this combination was used to evaluate the effects of two heat treatment procedures (HT1 and HT2) and two DB processes (using burnishing forces of 100 N and 300 N) on the tensile properties and surface integrity of LPBF 17-4PH SS cylindrical samples. The HT2 procedure, including annealing $({1200}^{\circ }$, $4 \mathrm{h})$, solution treatment (${1060}^{\circ }$, $1 \mathrm{h})$, cooling (${-70 }^{\circ }\mathrm{C},2 \mathrm{h}$), and ageing (${482}^{\circ }$, $4 \mathrm{h}$) led to yield limit, tensile strength, and Vickers hardness values of $\mathrm{Y}\mathrm{L}=1071 \mathrm{M}\mathrm{P}\mathrm{a}$, $\mathrm{T}\mathrm{S}=1410 \mathrm{M}\mathrm{P}\mathrm{a}$, and $523 \mathrm{H}\mathrm{V},$ respectively. The concept presented takes advantage of the combination of the transformation, precipitation and strain-hardening effects. The combined effect was most pronounced in the samples subjected to the HT2 procedure and subsequent DB (300 N), for which a retained austenite fraction of 6.93%, surface microhardness of ${563 \mathrm{H}\mathrm{V}}_{0.05}$ and the maximum values of the compressive axial and hoop RSs of $-1426.3 \mathrm{M}\mathrm{P}\mathrm{a}$ and $-1095.9 \mathrm{M}\mathrm{P}\mathrm{a}$, respectively, were measured. Full article

Burnishing technologies are a cheap and effective means of improving the surface integrity (SI) and performance of metal components. However, there is practically no information about the integral influence of the preceding turning process on the initial (pre-burnishing) SI. This study answers the question of how the white layer resulting from flank wear on the cutting insert in pre-turning affects the SI and fatigue limit, and determines the extent to which subsequent diamond burnishing (DB) is able to improve the SI and rotating bending fatigue limit of normalised, quenched and high-temperature-tempered C45 steel. The (DB)–SI–fatigue limit correlation was investigated using a holistic approach that took into account the effects of the dynamic pattern of flank wear on the initial SI. An explicit relationship was established between the flank wear, the affected surface layer structure and the fatigue limit. Increasing flank wear to the 60th minute intensified the formation of a gradient layer with finer and thinner grains that formed a texture. As a result, a synergistic effect was observed from turning with an insert operating for 60 min and subsequent DB, which maximised the fatigue limit (741 MPa). After 60 min, the structure of the affected layer changed qualitatively towards the formation of a nanostructured (white) layer, which reversed the trend, worsening the fatigue behaviour. As the thickness of the white layer increased, the fatigue limit was sharply reduced to below 560 MPa after the 90th minute. Regardless of the degree of flank wear, DB significantly improved the SI characteristics and increased the fatigue limit after turning with a worn insert, although the absolute dimensions of the positive DB effect depend on the initial SI and fatigue limit due to pre-turning. To achieve a synergistic effect, the cutting insert should be replaced with a new one after every 60 min of operation. Full article

This paper numerically and experimentally establishes a connection between shear deformation of the AISI 304 steel surface layer and the sliding velocity of a diamond indenter in multi-pass nanostructuring burnishing. Results of finite-element simulation of the process fully correspond to the experimental data obtained when changing the sliding velocity from 40 to 280 m/min after one and five tool passes. The experiment’s burnishing force was assumed to be 150 and 175 N, and feed was 0.025 mm/min. After surface machining, the maximum microhardness reached 400 HV_0.05 at the depth of 30 µm from the surface after five indenter passes with the sliding velocity values of 40 and 200 m/min and burnishing force of 175 N. Full article

CuZn39Pb3 leaded brass is one of the most widely used alloys in machining, with a 100% machinability index. However, there has been a lack of research on the effects of coldworking on surface integrity (SI) and operating behaviour of CuZn39Pb3 components. This study addresses this knowledge gap by examining the effects of three optimised combined processes on surface roughness, a key SI characteristic. Specifically, samples were subjected to a turning process followed by diamond burnishing (DB); this combined process was performed under three conditions: conventional flood lubrication (F), dry (D), and dry and cool-assisted (D+C) conditions. Cool-assisted conditions were achieved using a special device with a cold air nozzle operating on the vortex tube principle. The D and D+C conditions represent environmentally sustainable alternatives because they eliminate the use of cutting fluids, thereby reducing their adverse effects on both the environment and human health. The resulting surfaces obtained after each of the three optimised combined processes (F, D, and D+C) exhibited mirror-like finishes with minimum average roughness Ra values of 0.054, 0.079, and 0.082 μm, respectively. In addition, the F- and D+C-processes resulted in surface profiles with negative skewness and kurtosis values greater than three. Since roughness shape parameters are known to influence the operating behaviour of machined components, these processes are suitable for improving wear resistance in boundary lubrication regimes. Full article

Slide burnishing (SB) is a cheap and effective method for improving the surface integrity (SI) and operational behaviour (wear, fatigue, corrosion) of metal components. As its name suggests, SB is implemented through tangential sliding friction and is based on severe plastic deformation of the surface. The review presented here is dedicated to SB implemented using a non-diamond-based deforming element and aims to systematise the achievements from recent decades regarding SB’s effects on the SI, fatigue, wear and corrosion behaviour of metal components. Depending on the burnishing conditions (lubrication, cooling, assisting and their main effects on the treated surface), and based on the difference between the concepts of method and process, a classification of the types of SB processes was made based on the SB method—that is, conventional, sustainable, minimum quantity lubrication-assisted, special, hybrid and combined processes involving SB. Based on this classification, a critical analysis was conducted, viewed through the prism of correlations between the SB, SI and operating behaviour. With sustainability issues becoming increasingly relevant across all industries, more attention is being paid to sustainable SB processes. Because the finite-element method is a powerful and inexpensive tool that can be applied to the analysis of burnishing processes, we used it to build adequate finite-element models of SB processes. At the end of the paper, we outline avenues for future research on SB. Full article

Even though the foundations of diamond burnishing as a research topic were laid long ago, numerous scientific papers still deal with examining various aspects of the burnishing process today. One such aspect is the investigation of the 3D roughness parameters related to the tribological characteristics of the machined surface, which is detailed in the present study. In this study, the positive properties of slide friction diamond burnishing are presented through the examination of surface quality, which plays a key role in tribological assessment. This study analyzed the surface layer condition of X5CrNi18-10 stainless austenitic chromium–nickel steel test pieces after burnishing. Among the finishing operations, burnishing is an economical and low-environmental impact process. The study includes a description of the technological characteristics of turning and diamond burnishing processes. The main characteristics of the Abbott–Firestone curve are described, and parameter improvement factors are introduced. The experimental results and their evaluations are presented by analyzing the values of the Abbott–Firestone surface curves. The study concludes that the best improvement ratios of S_a (arithmetical mean height), S_q (root mean square height), S_z (maximum height) IS_a, IS_q, and IS_z roughness improvements were achieved when using the parameter combination v₂ = 55.578 m/min, f₂ = 0.050 mm/rev and F₄ = 50 N. Full article

There is a lack of information in the literature on the influence of technological heredity on surface integrity characteristics after diamond burnishing (DB). The present study fills this gap. Here, we present the effects of DB on the roughness parameters and surface microhardness of heat-treated C45 steel under conditions of changing initial roughness (Ra^init) due to wear on the cutting insert in the previous turning. The aim was to quantitatively assess the ability of DB to maintain sustainable surface integrity characteristics. We found that the service life of the cutting insert up to complete wear or fracture when operating at an optimal feed rate and cutting velocity was 163 min, at which point the roughness changed unevenly from an average roughness (Ra) value of 0.38 to 1.31 μm and an average height of the profile microroughness (Rz) value of 2.21 to 6.13 μm. Under conditions of an artificially created Ra^init (through different combinations of feed rate and cutting velocity) of 0.308 to 10.688 μm, DB provided Ra values in the range of 0.042 to 0.316 μm, with the surface microhardness varying from 461 to 568 HV. Stable Ra values were maintained from 0.042 μm to 0.089 μm, after which the Ra^init increased to 3.379 μm. Under production conditions, where the previous turning was performed at an optimal feed rate of 0.05 mm/rev and a cutting velocity of 180 m/min, DB provided a stable Ra of ≤0.059 μm of a resulting mirror-like surface during the first 90 min of operation of a new (unused) cutting insert, after which the Ra values increased linearly from 0.059 to 0.133 μm in the 150th minute. After 30 min of operation, until the cutting insert was completely worn, the microhardness after DB varied from 676 to 795 HV, the high surface microhardness resulting from a complex process of surface thermo-mechanical strengthening (including strain and transformation hardening) in the previous turning due to wear on the cutting insert. Full article

This study analyzed the surface layer condition of X5CRNI18-10 stainless austenitic chromium–nickel steel test pieces after burnishing. Among the finishing operations, burnishing is an economical and low-environmental-impact process. In special cases, grinding can be replaced by burnishing, so the same roughness can be achieved with much lower environmental impact. The aim of this study is to analyze the roughness of a surface machined by diamond burnishing using Kraljic matrices. The technological parameters used during the burnishing tests were burnishing speed, feed rate, and burnishing force. The full factorial experimental design method was used to carry out the experiments. Using Kraljic matrices, the optimum burnishing force was determined to select the best value of the surface roughness, and the change in surface roughness was investigated using full factorial experimental design for different technological parameter combinations. A special improvement ratio formula was developed to evaluate the effectiveness of the burnishing process with respect to 2D and 3D roughness parameters. Full article

The main goal of this study is to develop an optimized sustainable combined process, including sequential dry hard turning and dry smoothing diamond burnishing (DB), to improve the surface integrity (SI) and fatigue limit of heat-treated 42CrMo4 steel shafts and axles. A holistic approach was used based on a two-stage study: (1) optimization of dry hard turning under an average roughness Ra criterion and (2) selection of a suitable dry DB from three alternative DB processes, implemented with burnishing forces of 50, 100, and 150 N. With increasing burnishing force, the average roughness of Ra decreases, the microhardness increases, and the surface axial residual stresses increase in absolute value. However, the fatigue limit decreases, and at burnishing forces of 100 and 150 N, the fatigue limit is smaller than that obtained via the previous turning. The sustainable combined process achieves greater SI than consecutively applied conventional turning and DB under flood lubrication conditions. Dry DB at a force of 50 N increases the rotating bending fatigue limit by 20 MPa and the fatigue life by a factor of more than 70 compared to the previous dry turning. Full article

Chromium–nickel austenitic stainless steels are widely used in various industries after their initial hardness and strength are increased. Apart from low-temperature thermal–chemical diffusion, the mechanical properties can be improved by surface cold working (SCW). A cheap and reliable form of static SCW is diamond burnishing (DB), which drastically improves the surface integrity (SI) and hence the operational behavior of the processed component. To be maximally effective, the DB parameters must be optimized according to a relevant criterion, depending on the desired effect. For high fatigue strength and/or high wear resistance, complex experimental tests are necessary, which require significant time and financial resources. This study presents a cost-effective optimization approach based on the DB process–SI–operating behavior correlations. Using these correlations, in addition to the correlations between appropriately selected SI characteristics, the proposed approach relies on the control of only three easy-to-measure roughness parameters, namely the arithmetic average roughness, skewness, and kurtosis, which, in turn, depend on the governing factors of the DB process. Full article

This article presents results on the evolution of surface integrity, microstructure, mechanical characteristics, fatigue strength, and wear behavior of AISI 304 steel specimens after prolonged exposure (up to 746 days) to a natural seawater environment, specifically near the port of Varna, Bulgaria. The samples, having different shapes and sizes according to the respective tests, were divided into two main groups based on the finishing process: fine turning (FT) and diamond burnishing (DB). Additionally, fatigue FT specimens were polished to meet the standard requirements. Some of the cylindrical samples from both groups were heat-treated to dissolve the car-bides. No significant improvement in the corrosion resistance of the heat-treated samples (FT and DB) was observed compared with untreated samples after 746 days of immersion in seawater. Overall, all types of DB specimens showed less mass loss (indicating a higher corrosion resistance), higher static and fatigue strength, greater plasticity, and greater wear resistance than the corresponding FT specimens. Notably, pitting corrosion was observed on all specimens, as well as trac-es of intergranular corrosion in some FT specimens. The hardening DB effects have a complex impact on corrosion activity. The increases in dislocation density and the surface and internal energy of the subsurface layers intensify the nucleation of corrosion centers in the surface layers; however, the refined fibrous structure and significant reduction in the roughness slow down the development of corrosion. Therefore, the implementation of DB as a smoothing process will re-duce the surface energy, and hence will lead to further increases in corrosion resistance. Full article

Owing to their high producibility and resistance to corrosion, austenitic chromium–nickel steels are widely used in the chemical, petroleum, and food industries. However, their significant disadvantage lies in their poor structural performance, which cannot be improved by heat treatment. This significantly limits the usability of these steels in parts of machines that operate under friction loads. Hardening can be achieved by decreasing the size of grains and applying deformation-induced martensitic transformation. Nanostructuring burnishing (NSB) may be one of the technologies suited for producing parts of tribological assemblies with enhanced operating characteristics. Nanostructuring burnishing using a sliding indenter is being developed as a method of industrial surface nanocrystallization through severe plastic deformation used in the mechanical machining of various types of parts. This article investigates the possibility of enhancing the mechanical and tribological properties of nanocrystallized surfaces of austenitic steels, which are formed through nanostructuring burnishing using a tool with a natural diamond spherical indenter and a change in sliding speed from 40 to 280 m/min with one, three, and five passes. Increasing the tool sliding speed makes surface nanostructuring machining of big parts highly effective. This paper aims to establish the influence exerted by the sliding speed and number of indenter passes on the formation of a nanocrystalline structure, as well as on the modification of microhardness and residual stresses, texture, and tribological properties of the surface layer in the nanostructuring burnishing of AISI 304 steel. Transmission microscopy and microdurometry, 3D-profilometry, and tribological tests of surfaces nanocrystallized with the “ball-on-disk” scheme with dry and lubricated friction established the optimal values of speed and number of passes for a spherical indenter in nanostructuring burnishing. Full article

Additive manufacturing (AM)’s ability to produce customized products with reduced material wastage and other advantages helped the technology to gain popularity in many industries. However, its poor surface integrity is its weak side, and to overcome this, additional post-processes are essential. Slide diamond burnishing, known for its enhancement of surface roughness, residual stress, microhardness, and other properties, was combined with grinding in this research after 3D printing of MetcoAdd 17-4PH-A to mitigate the mentioned shortcomings. This study aimed to analyze the effects of each process on surface roughness, residual stress (both on the surface and in-depth), and microhardness. Workpieces were ground with the same parameters and burnished with four levels of force, feed, and number of passes. The L16 Taguchi experimental design was used to optimize the process parameters and to study their effects. For surface roughness, the optimum parameters were found to be 60 N force, 0.02 m/min feed rate, and three passes. The longitudinal surface residual stress has optimal values at 80 N force, 0.02 m/min feed rate, and four passes. In the case of transverse surface residual stress, the optimal values were 60 N force, 0.17 m/min feed rate, and three passes. Microhardness was maximized with 60 N force, 0.02 m/min feed rate, and one pass. Additionally, the in-depth residual stress for selected surfaces was investigated, and 100 N force showed a deep burnishing effect. Further multi-objective optimization using desirability function analysis found that the optimal parameters for all responses were achieved at the fourth burnishing force level (100 N), the first tool feed level (0.02 m/min), and the fourth number of passes level (four passes). Ultimately, both grinding and burnishing processes exhibited significant enhancements in the measured parameters. Full article