Surface Roughness Of Coatings Research Articles

ANALYZING THE EFFECTS OF MANUFACTURING PARAMETERS MODIFICATION ON FINAL SURFACE ROUGHNESS IN SELECTIVE LASER MELTING PARTS

Selective Laser Melting (SLM) is an additive manufacturing technique widely used today for producing metal components. This method enables the fabrication of geometrically complex parts while reducing costs and production time compared to traditional manufacturing techniques. However, a notable drawback of SLM is its tendency to produce high surface roughness and superficial defects such as balling, porosity, debris, and waviness. This study evaluates the effects of modifying two manufacturing parameters—scanning speed and laser power—on the final surface roughness. To achieve this, cylindrical specimens were fabricated using various combinations of these parameters, and the resulting surface roughness metrics (Sa, Sq, Ssk, Sku, Sdr, among others) were measured using an optical 3D surface roughness measurement instrument. A Taguchi L8 design was applied to analyse the influence of the manufacturing parameters on the measured roughness characteristics. This study investigates the influence of laser power and scanning speed on surfaces manufactured through Selective Laser Melting (SLM) and their effects on the previously described roughness parameters. The authors observed that the manufacturing parameters have varying impacts on the final surface roughness of components produced via SLM. Due to the inherent characteristics of the process, a specific combination of parameters that reduces roughness within a specimen's layer may increase roughness at the layer boundaries. These findings underscore the complex relationship between manufacturing parameters and surface roughness in SLM-produced parts, emphasizing the need for strategies, such as surface finishing post-treatments, to achieve the desired surface quality.

Effect of chairside polishing systems on the surface roughness of different CAD-CAM denture base materials

Adjusting and polishing a denture base affects surface roughness and, consequently, microbial adhesion. Since various computer-aided design and computer-aided manufacturing (CAD-CAM) denture base materials are available, the efficiency of chairside polishing systems to achieve a proper surface roughness should be investigated. The purpose of this in vitro study was to compare the surface roughness of milled and 3-dimensional (3D) printed denture base materials with that of heat-polymerized acrylic resin after the use of 2 different chairside polishing systems. Heat-polymerized (control), milled, and 3D printed denture base materials were tested. Laboratory polished and unpolished denture bases served as positive and negative controls. Specimens were divided into 2 chairside silicone polishing systems (AcryPoint system and Exa technique). Surface roughness was measured before and after polishing. Surface morphology of the unpolished and polished specimens was observed via scanning electron microscopy. The surface hardness of unpolished specimens was measured using a Vickers hardness tester. Stress-strain behavior of the silicone matrix and abrasive filler size of each polisher was assessed. The effects of denture base materials and polishing systems on surface roughness and hardness were evaluated using 1-way, 2-way, and repeated measures analyses of variance (ANOVA) (α=.05), along with Weibull proportional hazards regression to assess the likelihood of achieving clinically acceptable surface roughness. The Spearman correlation assessed the relationship between the hardness of unpolished denture bases and final surface roughness. The surface roughness of all denture bases decreased with increased polishing duration, reaching a plateau after 60 seconds. For the heat-polymerized and milled dentures, the Exa technique consistently yielded lower roughness than the AcryPoint system (P<.001). Conversely, both polishing systems produced comparable surface roughness on the 3D printed denture base. The Vickers hardness of the unpolished milled denture was significantly higher than of the others (P=.010). The stress-strain behavior of the polisher matrix revealed distinct characteristics between coarse or medium and fine polishers within each polishing system. The abrasive filler size of the AcryPoint coarse polisher was relatively larger than that of the Exa technique. Regardless of polishing protocols, the 3D printed denture base exhibited the highest surface roughness, followed by heat-polymerized and milled denture bases. The surface roughness of the polished denture was not related with the material hardness. For heat-polymerized and milled dentures, a chairside silicone polishing system can be used to attain a level of surface roughness similar to that of laboratory polishing, depending on the properties of the chairside silicone polishing system. The data that support the findings of this study are available upon request from the corresponding author.

Pressure Effect on Surface Roughness of Gradient Chromium-doped Diamond-like Carbon Coatings under High Temperature

Abstract In this paper, the pressure effect of surface roughness of four gradient chromium-doped diamond-like carbon (GCD-DLC) coating is systemically studied in argon annealing and high pressure annealing under high temperature. After HIPping annealing, the surface roughness of the hydrogen-free group (GCr and GCrSi) decreased slightly. However, for the two hydrogen-containing GCD-DLC coatings (DCr and DCrSi), especially the DCr coating, the roughness increased significantly. The changes in surface roughness of the hydrogen-free group and the hydrogen-containing group after high-pressure annealing are opposite. The surface roughness of the DCr coating increased significantly after 500°C HIP annealing, which is attributed to the pores on the coating surface. Only the surface morphology of the DCr coating exhibited significant changes. Numerous voids appeared on the surface of the DCr5H coating after 500°C HIP annealing. There were significant differences in the size and shape of these voids compared to those after 500°C argon annealing. The voids on the coating after argon annealing were larger than those after HIP annealing. The formation of pores is associated with the breaking of carbon-hydrogen bonds and the subsequent release of hydrogen. This is because high pressure slows down the transformation from sp3 carbon bonds to sp2 carbon bonds. Simultaneously, high pressure also slows down the release of hydrogen within the coatings.

Achieving precise graphenization of diamond coatings below the interfacial thermal stress threshold

Abstract Diamond coatings possess numerous excellent properties, making them desirable materials for high-performance surface applications. However, without a revolutionary surface modification method, the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces. This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage, without causing damage to the metal substrate. Through experiments and simulations, the influence mechanism of surface graphitization and interfacial thermal stress was elucidated, ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness. Compared to the original diamond coatings, the obtained surfaces exhibited a 63%–72% reduction in friction coefficients, all of which were below 0.1, with a minimum of 0.06, and a 59%–67% decrease in specific wear rates. Moreover, adhesive wear in the friction counterpart was significantly inhibited, resulting in a reduction in wear by 49%–83%. This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties. This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces, with the potential to significantly enhance the performance and expand the application range of diamond-coated components.

Formation of Superhydrophobic Coatings Based on Dispersion Compositions of Hexyl Methacrylate Copolymers with Glycidyl Methacrylate and Silica Nanoparticles.

In the last decade, the task of developing environmentally friendly and cost-effective methods for obtaining stable superhydrophobic coatings has become topical. In this study, we examined the effect of the concentrations of filler and polymer binder on the hydrophobic properties and surface roughness of composite coatings made from organic-aqueous compositions based on hexyl methacrylate (HMA) and glycidyl methacrylate (GMA) copolymers. Silicon dioxide nanoparticles were used as a filler. A single-stage "all-in-one" aerosol application method was used to form the coatings without additional intermediate steps for attaching the adhesive layer or texturing the substrate surface, as well as pre-modification of the surface of filler nanoparticles. As the ratio of the mass fraction of polymer binder (Wn) to filler (Wp) increases, the coatings show the lowest roll-off angles among the whole range of samples studied. Coatings with an optimal mass fraction ratio (Wn/Wp = 1.2 ÷ 1.6) of the filler to polymer binder maintained superhydrophobic properties for 24 h in contact with a drop of water in a chamber saturated with water vapor and exhibited roll-off angles of 6.1° ± 1°.

The effect of whitening toothpastes on the surface properties and color stability of different ceramic materials

ObjectivesThis study aimed to evaluate the effect of whitening toothpastes on the surface roughness and colour change of CAD-CAM materials.Materials and methodsA total of 96 samples (2 × 10 × 12 mm3) were prepared from Cerasmart (CS) and Celtra Duo blocks. Celtra Duo samples were divided into two groups. One group was fired with glaze paste (CDG) and the other was not treated (CD). All groups were then divided into 4 subgroups (n = 8). The groups were brushed with conventional (Colgate™ Max Fresh), silica (Opalescence™), charcoal (Curaprox™ Black in White) and blue covarine (Signal™ White Now) toothpastes for 30,000 brushing cycles. The initial and final surface roughness values were measured with contact profilometer and a dental spectrophotometer used for obtaining colour values. One sample from each brushed group was analyzed using a scanning electron microscope. Data was analyzed with Kruskal-Wallis and Mann-Whitney tests (p = 0.05).ResultsThe surface roughness of CS samples brushed with Opalescence™ and Curaprox™ was significantly higher than CD and CDG. Surface roughness change values of CS samples brushed with Curaprox™ were significantly higher than the CD and CDG. Curaprox™ brushed samples showed significant difference in colour change values for all materials.ConclusionsBrushing increases the surface roughness of CAD-CAM ceramic materials. The roughness of resin-based materials is higher than zirconia-reinforced lithium silicates. Silica-contained toothpastes may cause discoloration of nanoceramic and zirconia-reinforced glass ceramic restorations.Clinical relevanceIt should be clinically considered that whitening toothpastes may cause roughness in ceramic materials and change the desired color.

Experimental investigations of chemo-mechanical magneto-rheological finishing of Al-6061 via composite magnetic abrasive

ABSTRACT To achieve flawless soft material surfaces, defects and irregularities must be eliminated. Traditional abrasive-mixing techniques frequently produce surface flaws as a result of abrasive embrittlement, resulting in poor surface-quality. As a result, ensuring an immaculate finish is critical for these surfaces. In contrast, the chemo-mechanical magneto-rheological finishing (CMMRF) process, which employs a composite magnetic abrasive (CMA)-based smart fluid, has proven to be extremely effective at producing nano-finished surfaces. This study used a central-composite-rotatable design (CCRD) based on response surface methodology (RSM) to analyze how CMAs variables, slurry-based parameters, and polishing time affect final surface roughness (R a ) and percentage change in roughness (%∆R a ) for Al-6061. The CMMRF process resulted in a superior Al-surface finish (R a ) of 29 nm and a %∆R a of 91.23%. Statistical models predicted R a and %∆R a values, which matched experimental results. Characterization tests on the final Al-surface revealed significant reduction in initial machining scratches and valleys, resulting in a superior mirror-polished surface via CMA-based polishing.

Abrasive challenge effects on enamel and dentin from irradiated human teeth: an in vitro study.

This study aimed to evaluate the effects of radiotherapy (RT) and chemoradiotherapy (CRT) on the wear and surface roughness of in vitro irradiated human enamel and dentin subjected to abrasive challenge. Enamel and dentin specimens (n = 42) were prepared from teeth donated by healthy patients and those with head and neck cancer who had received radiotherapy (RT) or chemoradiotherapy (CRT). The specimens were categorized into three groups: control, RT, and CRT (n = 14 per group for both enamel and dentin). These samples were subjected to an in vitro abrasive experiment using a brushing machine, followed by wear and surface roughness assessments with a confocal laser scanning microscope conducted before and after the abrasive challenge, considering both exposed and non-exposed areas. Statistical analysis used Shapiro-Wilk tests for normality, Wilcoxon tests for comparing two means, and Kruskal-Wallis tests. A significance level of 5% was adopted. In enamel specimens, wear profile values ​​of CRT and RT groups were not different from the control (p > 0.05). The RT group presents lower step values than the CRT and control groups (p < 0.001). No significant difference in final surface roughness was observed in all groups (p > 0.05). In dentin specimens, no significant difference in wear profile and step was observed in all groups (p > 0.05). However, CRT and RT groups present higher values in final surface roughness (p < 0.001). The exposure to ionizing radiation (associated or not to chemotherapy) influenced the surface roughness of dentin and the wear (step) of enamel after the in vitro abrasive challenge.Trial registration: Ethical procedures were approved by the FORP/USP Research Ethics Committee (CAAE: 61308416.4.0000.5419), and Hospital do Câncer de Barretos/Fundação Pio XII (CAAE: 61308416.4.3001.5437).

Multi-Response Optimization of Single Point Incremental Forming of Al 6061 Sheet Through Grey-Based Response Surface Methodology

The single point incremental forming process (SPIF) is materialized to form the desired shapes in low-cost sheet metal processing and well suited for low batch components and customized designs. Many modifications have been attempted in recent years to maximize the formability, geometric accuracy and quality of the SPIF formed parts. In this work, an attempt has been made to analyse the influence of process parameters namely ball tool diameter, step size, spindle speed and sheet thickness on final wall thickness, forming force and surface roughness. The optimized results exhibit the desirable formability when the roller ball tool diameter of the tool is 12 mm. The results also project that formability of the sheet metal is minimized when the spindle speed is increased and the ball diameter maximizes the accuracy and surface roughness. Also minimizing the step size increases the product quality features. Upon conducting this multi-response optimization by grey based response surface methodology (RSM) technique It is identified that 12 mm ball diameter of the tool, 0.25 mm step size, 2445 rpm spindle speed, and 2 mm sheet thickness are the obtained optimized SPIF process parameters as confirmed through confirmation experiments.

Effect of heat treatment before fast multiple rotation rolling on friction surfaced Al–Si–Cu alloy

In this study the effect of combination of heat treatment of consumable rod and solid solution heat treatment before fast multiple rotation rolling (FMRR) processing on microstructure, mechanical property and wear resistance of Al–Si–Cu alloy friction surfaced on commercial pure aluminum alloy were investigated. Results show that after the FMRR process, there is a significant reduction (99% reduction) in the friction surfaced coating surface roughness. The surface roughness after FMRR processing in the coatings created by homogenized and solid solution treated consumable rod is 0.74 ± 0.12, and 0.56 ± 0.08 μm, respectively. In the coating created by homogenized rod the minimum grain size (1.7 ± 0.2 μm) formed in the FMRR processed layer. Using homogenized consumable rod and FMRR processing by rotational speed of 3000 rpm and traverse speed of 140 mm/min, the maximum hardness (9.8 ± 0.3 GPa) and minimum wear rate (4.6 ± 0.1 μg/m) created at processed layer. FMRR processing by rotational speed of 3000 rpm and traverse speed of 140 mm/min, result in 27 and 24 % increasing in hardness at friction surfaced coating created by homogenized and solid solution treated consumable rods, respectively.

Preparation of porous composite coatings to suppress surface charge movement and reduce electrical resistivity

In this work, Cr2O3/TiO2 composite coatings were prepared on α-Al2O3 insulating ceramic matrix surface by screen printing and solid phase sintering methods to yield an average film thickness of about 14.10 μm. Scanning electron microscopy (SEM) revealed changes in the pore structures of the coatings at different TiO2 contents. The atomic force microscopy (AFM) analysis of the coating surface roughness suggested a TiO2 content of 0.025 mol to yield the best surface roughness and pore structure of the coating. The calculation showed an increase in the energy level of the deep trap center on the surface from 1.506 eV to 1.547 eV, reaching a maximum. The surface resistivity of insulating ceramics decreased from 1016 Ω to 1012 Ω. The formation of deep surface traps and the decrease in surface resistivity promoted charge dispersion and suppressed the formation of flashover channels, effectively improving the surface flashover voltage of the ceramics.

Improving the suppression of charge movement by porous chromium oxide coating

A chromium trioxide coating was prepared on the surface of electronic ceramics by screen printing, and solid-phase sintering was carried out at 1350 °C. The surface roughness and surface resistance characteristics of composite coatings with different chromium trioxide contents were studied. The analysis results indicate that the average thickness of Cr2O3 coating is about 19.89 μm. The main crystal phase is (Al0.9Cr0.1)2O3. SEM shows that the surface "pores" and surface roughness of the coating change with the content of Cr2O3. AFM shows that when the Cr2O3 content in the coating is 0.0921 mol, the surface roughness changes the most, and the corresponding surface resistivity of Al2O3 insulating ceramics decreases to the lowest, from 1016 Ω to 1012 Ω. An increase in surface roughness can lead to changes in the incidence angle of electrons, reducing the probability of electron surface collision. The lower the surface resistivity, the better the high-voltage breakdown resistance of vacuum ceramic devices, thereby improving the surface flashover performance of ceramics.

Analysis of a Regression Model for Creating Surface Microgeometry after Machining Zirconia YML Used for Dental Application.

This article focuses on research in the machining of zirconia crowns for dental implants. Its goal is to find the most suitable cutting parameters that significantly affect the final surface roughness of the crowns for dental implants. This study conducts investigations and experiments to specify the cutting parameters that achieve the optimal surface roughness of zirconia crowns for dental implants. The experiments were designed to precisely determine the cutting parameters that influence the surface roughness of zirconia crowns. The results of this study provide important insights for improving the manufacturing process of zirconia crowns with the specified most suitable cutting parameters. This research contributes to the enhancement of zirconia crown manufacturing techniques and the improvement in the quality and effectiveness of dental implants.

Effects of spraying parameters and heat treatment temperature on microstructure and properties of single-pass and single-layer cold-sprayed Cu coatings on Al alloy substrate

Exploring the deposition of single-pass and single-layer pure Cu coatings on Al alloy substrate through high-pressure cold spray technology is a crucial endeavor with significant implications for advancing the utilization of such coatings. Regrettably, research in this specific area remains scarce, highlighting the need for further investigation and understanding. This study examined the characteristics of cold-sprayed Cu coatings deposited on a 6061 T6 aluminum alloy substrate under varying gas temperatures and pressures, and explored the effects of subsequent heat treatment on the microstructure and mechanical properties of the Cu coatings. The morphology, phase composition, surface roughness, thickness, porosity, microstructure, shear strength, and microhardness of the cold-sprayed Cu coatings were systematically analyzed. The findings indicated that the spraying parameters had a substantial impact on the properties of the Cu coatings. Specifically, increased gas pressure led to rougher surfaces and lower porosity, whereas higher gas temperature produced smoother surfaces and also reduced porosity. At 800 °C and 4.0 MPa, the Cu coatings exhibited the lowest surface roughness, measuring 8.03 μm. Conversely, at 800 °C and 5.5 MPa, the Cu coatings demonstrated the lowest porosity, at 0.26 %. Moreover, the microstructure analysis showed evidence of dynamic recrystallization in the deposited Cu particles, contributing to enhanced mechanical properties. Following this, the influence of heat treatment on the microstructure and properties of the cold-sprayed Cu coatings was examined. The results demonstrated that annealing at different temperatures induced changes in the interfacial microstructure, with the formation of intermetallic compounds between the Cu coating and Al alloy substrate. This interdiffusion phenomenon led to improved bonding strength and mechanical properties of the Cu coatings, as evidenced by increased shear strength. After undergoing heat treatment at 400 °C, the Cu coatings exhibited the highest shear strength, measuring 49.89 MPa. However, excessive heat treatment temperatures resulted in the formation of cracks and a decrease in mechanical properties.

Multi-physics simulation for predicting surface roughness of laser powder bed fused parts after laser polishing

Laser powder bed fusion (L-PBF) uses a controlled laser beam to melt specific regions of a metal powder bed in a layer-by-layer fashion to fabricate parts with an intricate geometry. However, due to the stochastic nature of the L-PBF process, many defects may occur during the build process, including distortion, porosity, and high surface roughness. A poor roughness of the upper surface is frequently associated with impaired mechanical properties and a lower corrosion resistance. Thus, laser polishing (LP) is commonly employed to smooth the surface of the component following the build process. The surface finish of the polished part is dependent not only on the initial morphology of the surface, but also the processing conditions employed in the polishing process (i.e., the laser power, scanning speed, and hatching space). The surface profile is also influenced by physical phenomena such as the surface tension force, recoil pressure, and Marangoni force. The present study thus proposes an integrated framework based on discrete element method (DEM) and computational fluid dynamics (CFD) simulations which takes account of all of these factors to predict the final surface morphology and roughness of L-PBF components following LP processing. The validity of the simulation model is confirmed by comparing the calculated mean surface roughness of the polished components (Sa)with the experimental values. It is found that the maximum error of the simulation results for different initial surface morphologies and LP processing conditions is less than 6.8 %.

A major functional role of synovial fluid is to reduce the rate of cartilage fatigue failure under cyclical compressive loading

ObjectiveBased on our recent study, which showed that cartilage fatigue failure in reciprocating sliding contact results from cyclical compressive forces, not from cyclical frictional forces, we hypothesize that a major functional role for synovial fluid (SF) is to reduce the rate of articular cartilage fatigue failure from cyclical compressive loading. DesignThe rate of cartilage fatigue failure due to repetitive compressive loading was measured by sliding a glass lens against an immature bovine cartilage tibial plateau strip immersed in mature bovine SF, phosphate-buffered saline (PBS), or SF/PBS dilutions (50% SF and 25% SF; n=8 for all four bath conditions). After 24 hours of reciprocating sliding (5,400 cycles), samples were visually assessed and if damage was observed, the test was terminated; otherwise, testing was continued for 72 hours (16,200 cycles), with solution refreshed daily. ResultsAll eight samples in the PBS group exhibited physical damage after 24 hours, with an average final surface roughness of Rq=0.210±0.067 mm. The SF group showed no damage after 24 hours; however, two of eight samples became damaged after 72 hours, producing a significantly lower average surface roughness than the PBS group (Rq=0.059±0.030 mm; p<10−4). For the remaining groups, at 72 hours one of eight samples damaged in the 50% SF group, and five of eight samples damaged in the 25% SF group. ConclusionsThe results strongly support our hypothesis, showing that decreased amounts of SF in the testing bath produces increased rates of fatigue failure in cartilage that was subjected to reciprocating sliding contact.

Cold Gas Spraying Copper Metal On AlN Ceramics as an Alternative to Thick DBC Substrates for Power Electronics

Abstract This study investigates the use of cold gas spraying (CGS) as a low-temperature additive manufacturing method to bond copper onto aluminum nitride (AlN) substrates for electronic packaging of high-power applications. While direct bond copper (DBC) technique is commonly used, it has limitations due to the large mismatch in coefficient of thermal expansion, which affects substrate reliability. This work employed cold gas spraying (CGS) to mechanically bond Cu on AlN. The study explores the effect of multiple sprays, spray angle and spraying direction on deposition thickness, coating surface roughness, and deposited volume through a factorial design of experiments (DOE). The results, based on optical and scanning electron microscopy combined with profilometry data, showed that coatings sprayed at a 60° angle had a smoother profile topography and less surface roughness than those sprayed at a 90° angle. After depositing 10 layers, a surface roughness (Sa) of around 30 µm and a coating thickness of over 300 µm were successfully attained. These findings provide valuable insights into the processing factors affecting the growth and quality of copper coatings on AlN substrates via multiple sprays, thus enabling the realization of CGS technology as a potential solution to DBC substrates for electronic packaging of wide-bandgap semiconductors.

A comparison of additive manufactured to injection molded Martian regolith based polymer matrix composites

The completed study investigated the creation of Martian regolith simulant composite parts using injection molding and additive manufacturing. Traditional manufacturing techniques such as injection molding are not feasible on the Martian surface therefore in-situ processes must be developed using additive manufacturing processes to prepare habitats prior to having a human presence on the surface. The goal of this study was to investigate the impacts of additive manufacturing on the material property values between parts made using traditional injection molding and additive manufacturing. Martian regolith simulant composite pellets were created by combining a Martian regolith simulant at 40 wt% loading with polypropylene via twin screw extrusion. This material was then used to create test specimens using injection molding and additive manufacturing. Samples underwent tensile, flexural, Izod impact, and immersion density tests according to ASTM International and standardized test instructions. Additive manufactured parts saw a nearly 40% reduction in tensile and flexural strength with more than double the tensile modulus when compared to injection molded parts. The flexural modulus for additive manufacturing was around 36% that of the injection molded part with a minor decrease in density of around 13%. The collected test results suggested that while there were differences in the material property values between the manufacturing processes, a more interesting foaming behavior of the extrudite was observed during the additive manufacturing process resulting in an extremely rough and pitted surface. This rough surface finish was a stark comparison to the smooth injection molded parts. This observed foaming behavior in the polymeric composite material during thermal processing prompted the theory that thermal releases from the Martian regolith simulant was the most likely cause of the observed differences. Pellet surface moisture tests, Martian regolith simulant thermogravimetric analyses, and literature reviews of thermal decomposition of the Martian regolith simulant constituents revealed that most likely olivine releases oxygen and hydrated silica releases water during the thermal processing of the Martian regolith simulant composite. During a closed mold process such as injection molding, these volatile gases are forced out of the part by the pressures of the molding process, but in an open to atmosphere process such as additive manufacturing these gases foam to the surface during cooling leaving the part with an inferior surface finish.

Microstructural and tribological properties of cold sprayed high content SiCp/Al coating by SiCp mild-oxidation treatment

This paper presents the results of the influence of irregular SiC particles, treated by mild-oxidation at 1100 °C, on deposition behavior (deposit rate, surface finish roughness), and deposition body (microstructure, friction, and wear). Coatings are obtained using the cold-sprayed method, employing a powder mixture comprising 36 vol% irregular SiC powder treated by mild-oxidation and 64 vol% aluminum powder as feedstock. Results show that the silicon carbide particles are treated by mild-oxidation, the external surface of silicon carbide particles is predominantly composed of soft ceramic silica, and the particle edges are passivated. The results indicate that, under identical cold-sprayed process conditions, both the deposition amount of the coating and the retention amount of SiC particles increased. The particle fragmentation and particle distribution of SiC are obviously improved. The coating did not exhibit any harmful phases. Local weak metallurgical bonding is found at the interface of SiCp and Al matrix. Furthermore, the coating's porosity decreased, after SiCp mild-oxidation, the friction coefficient (0.5716) is decreased by 12.9 %, and the wear amount (0.159 mm3/N·m) is decreased by 64.7 %. A dense and uniformly distributed aluminum matrix composite coating with a high SiC particles content is achieved.

Effect of hatch spacing in selective laser melting process of Ti-6Al-4V alloy on finished surface roughness: A computational study

The Selective Laser Melting (SLM) process is a promising additive manufacturing technology for producing complex metal parts. However, this process has certain limitations, including lack of fusion and defects, which can hinder its industrial applications. These challenges can be addressed by determining the appropriate overlap percentage parameters. This study used numerical simulation to explore the effect of overlap percentage on multi-track melting in the SLM process for Ti-6Al-4V. The simulation results categorize the multi-track melting morphologies into two distinct groups. The first group, (0% to 40% overlap), displays consistent surface roughness with an average Ra value of 7 µm. In contrast, the second group (50% to 60% overlap), shows non-uniform shapes. Specifically, the three central tracks in this group present an Ra value of approximately 4 µm. However, when all five tracks of this group are taken into account, the average Ra rises to 14 µm. These differences in surface roughness can be attributed to factors like energy density and the Marangoni effect. Both melt pool depth and shrinkage depth in the overlap area are significant as they might contribute to the risk of the lack of fusion defects. The insights from this research hold potential in shaping scanning pattern strategy design.