The effect of copper concentration on the wear resistance of composites based on recycled ShKh15 steel during friction with current collection

The current-voltage characteristic, wear resistance, and friction surface roughness of baked model copper-graphite-ShKh15 steel composites are determined. It is shown that the composites containing under 10% and above 50% Cu produce a friction zone with low conductivity and wear resistance. The composites containing 15–20% Cu produce a friction zone with relatively high conductivity and wear resistance. The maximum parameters of the roughness (R _a = 2.98 μm and R _z = 24.5 μm) appear on the friction surface of the material containing 50% Cu.     

High Velocity Oxyfuel Deposition for Low Surface Roughness PS304 Self-Lubricating Composite Coatings

Efforts were made to achieve lower (R _q < 0.1 μm) initial RMS roughnesses of PS304 coatings so that they may be considered for foil bearings operating under increasingly severe conditions that result in smaller air film thicknesses. Attainable roughness of conventional plasma-sprayed PS304 coatings has been typically R _q > 0.25 μm, as limited by porosity in the deposited coating and surface irregularities correspondingly formed upon finishing. Initial attempts at achieving dense coatings by instead using a high-velocity oxyfuel (HVOF) flame-spraying process failed due to insufficient heating and softening of the NiCr and Cr ₂ O ₃ constituents of the PS304 feed powder, which rebounded from the steel target substrate and resulted in low deposition yield. Efficient HVOF deposition by a hydrogen-fueled system was achieved using NiCr and Cr ₂ O ₃ constituent particles of reduced size that were more effectively heated. The resultant dense coatings provided roughnesses as low as R _q = 0.05 μm upon polishing. Tribological performance of these HVOF coatings was evaluated against Inconel X-750 in thrust-washer tests at a sliding speed of 5.4 m/s, with contact pressures of 20 and 40 kPa, and ambient or 500°C temperatures. The wear and friction performances in direct sliding contact, as would exist upon loss of separating air-bearing film, of the PS304 coatings produced by HVOF are found to be similar to those deposited by the plasma spray process.     

Effect of graphene addition and tribological performance of Al 6061/graphene flake composite

Graphene, no wonder has attracted a significant research interest due to its extensive physical properties at its single atomic thickness and 2D morphology. The current studies focus on the role of graphene in reducing the wear and frictional coefficient of Al 6061–graphene-reinforced metal–matrix composites (MMC’s). Reinforcement chosen is 0.3, 0.6 and 0.9 wt% of graphene to investigate the self-lubricating property under dry wear condition and processed through the ultrasonic liquid processor. The dry frictional wear test was carried out using pin-on-disc tribometer to evaluate the effect of graphene content in the composites under various normal load (5, 10, 15 N) and disc sliding speed (0.4, 0.8, 1.2 m/s) conditions. The results show that there is a significant increase in the hardness and wear resistance and a reduction in the coefficient of friction (μ) values compared to pure alloys. Arithmetic mean surface roughness values (R_a), max profile peak (R_p) and max valley depth (R_v) are found to be comparatively lower than the pure alloy. Due to the tribological potential coupled with improved strength and surface roughness values, Al 6061–graphene composite are excellent candidates for all applications where it is subjected to Friction and wear.     

Micromorphological characterization of zinc/silver particle composite coatings

The aim of this study was to evaluate the three‐dimensional (3D) surface micromorphology of zinc/silver particles (Zn/AgPs) composite coatings with antibacterial activity prepared using an electrodeposition technique. These 3D nanostructures were investigated over square areas of 5 μm × 5 μm by atomic force microscopy (AFM), fractal, and wavelet analysis. The fractal analysis of 3D surface roughness revealed that (Zn/AgPs) composite coatings have fractal geometry. Triangulation method, based on the linear interpolation type, applied for AFM data was employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The surface fractal dimension D_f, as well as height values distribution have been determined for the 3D nanostructure surfaces. Microsc. Res. Tech. 78:1082–1089, 2015. © 2015 The Authors published by Wiley Periodicals, Inc.     

Performance and surface alloying characteristics of Cu–Cr and Cu–Mo powder metal tool electrodes in electrical discharge machining

The main objective of this study is to investigate the effect of Cu–Cr and Cu–Mo powder metal (PM) tool electrodes on electrical discharge machining (EDM) performance outputs. The EDM performance measures used in the study are material removal rate (MRR), tool electrode wear rate (EWR), average workpiece surface roughness (R_a), machined workpiece surface hardness, abrasive wear resistance, corrosion resistance, and workpiece alloyed layer depth and composition. The EDM performance of Cu–Cr and Cu–Mo PM electrodes produced at three different mixing ratios (15, 25, and 35 wt% Cr or Mo), compacting pressures (P_c = 600, 700, and 800 MPa), and sintering temperatures (T_s = 800, 850, and 900 °C) are compared with those machined with electrolytic Cu and Cu PM electrodes when machining SAE 1040 steel workpiece. Analyses revealed that tool materials were deposited as a layer over the work surface yielding high surface hardness, strong abrasion, and corrosion resistance. Moreover, the mixing ratio, P_c, and T_s affect the MRR, EWR, and R_a values.     

Influence of eccentricity on roughness distributions in side milling

In this paper, a numerical model was used based on the tool-piece geometric intersection, which enables the determination of a roughness profile as a function of feed, tool radii and tool eccentricity in side milling processes. Average roughness R_a and peak-to-valley roughness R_t were obtained for a group or family of tools, defined by an average radius value and a standard deviation value of all tool radii. The Monte Carlo method was used to generate N random combinations of radius values for each family, according to a normal distribution. The model was validated by means of experimental tests. For each family of tools, roughness distributions were obtained at different feed values and for different eccentricity values. It was found that the higher eccentricity, the more asymmetrical roughness distributions become.     

Sinusoidal profile precision roughness specimens

The design, specifications, fabrication, testing and potential use of a series of sinusoidal profile precision roughness specimens are described. These specimens were designed primarily to provide a means for optimum transfer of an accurate roughness average R_a value from primary to secondary laboratories. However, properties of the specimens also make them very useful for evaluating instrumentation and computational algorithms designed to measure the statistical parameters and functions now being investigated in many laboratories. Specimens with an R_a value of 1.0 μm and spatial wavelengths of 40, 100 and 800 μm are being fabricated. For the wavelength of 100 μm, specimens are also being fabricated with R_a values of 3.0 and 0.3 μm. Fabrication using numerically controlled diamond lathes has produced specimens with very high quality sinusoidal profile waveforms with uniform R_a values across the surfaces and with very low amounts of waviness over a test area of about 2 cm².     

Comparison between precision roughness master specimens and their electroformed replicas

Two random profile precision roughness calibration specimens with R_a = 0.028 and 0.043 μm are compared with their electroformed replicas. Measurements of surface texture and roughness parameter values show very good agreement. Fluctuations in the R_a values across the replicas track those across the masters to within 1.8 nm. However, the form errors of the replicas, approximately 0.6 μm over a 3.2 × 2.6 mm² area, are much bigger than those of the masters, and their hardness (HV = 243) is not as good as the master specimens' (HV = 852).     

The effect of surface treatments on the microroughness of laser-sintered and vacuum-cast base metal alloys for dental prosthetic frameworks

This study aimed to evaluate the effect of four chemomechanical surface treatments on the surface average microroughness and profile of laser‐sintered and vacuum‐cast dental prosthetic structures. Square‐shaped blocks (10 mm × 10 mm × 1.5 mm) were prepared as follows: (1) laser‐sintered Co? Cr (L) (ST2724G); (2) cast Co? Cr (C) (Gemium‐cn); and (3) cast Ni? Cr? Ti (T) (Tilite). Specimens of each alloy group were randomly divided into five subgroups (n = 10 each), depending on the conditioning method used: (1) no treatment (control); (2) sandblasting (125 μm Al₂O₃‐particles); (3) silica coating (50 μm silica‐modified Al₂O₃‐particles); (4) oxidation; and (5) oxidation plus opacification. Subgroups 2 and 3 represent “inner” pretreatments proposed for ceramometal restorations to improve the metal surface area available for luting cements. Subgroups 4 and 5 are the “outer” pretreatments required for bonding the aesthetic veneering ceramics to the underlying metal frameworks. Average surface roughness (Ra/μm) was determined using a surface profilometer. Data were analyzed by two‐way ANOVA and Student–Newman–Keuls tests (α = 0.05). Metal surface topography was SEM‐analyzed. Despite the inner pretreatment applied, L samples resulted in the highest microroughness (P < 0.001), whereas sandblasting produced a surface‐smoothing effect in cast specimens. After oxidation, a significant increase in surface roughness occurred in all groups compared with controls, L specimens being the roughest (P < 0.001). Opacification caused a flattening effect of all oxidized structures; all opacified groups resulting in similar microroughness. Laser sintering of Co? Cr enhances the roughness of metal structures, which may improve the frameworks' microretention of the cements, and of the opaquer before the copings are veneered with the aesthetic ceramics. Microsc. Res. Tech. 75:1206–1212, 2012. © 2012 Wiley Periodicals, Inc.     

Electrolytic Plasma Surface Polishing of Complex Components Produced by Selective Laser Melting

The applicability of electrolytic plasma surface polishing to complex components produced by selective laser melting (SLM) is analyzed. By electrolytic plasma polishing by electrolyte spraying, the surface quality of components produced by SLM may be improved. This technology is found to decrease the surface roughness from R_a = 5.6 μm to 1.4 μm. The optimal pressure of the electrolyte jet is 0.02–0.05 MPa. At high pressures, the process becomes unstable. By electrolytic plasma polishing on the basis of electrolyte jets, uniform external and internal surface roughness of components produced by SLM may be ensured.     

Surface micromorphology of dental composites [CE‐TZP]‐[Al2O3] with Ca+2 modifier

The objective of this study was to characterize the three‐dimensional (3D) surface micromorphology of the ceramics produced from nanoparticles of alumina and tetragonal zirconia (t‐ZrO₂) with addition of Ca⁺² for sintering improvement. The 3D surface roughness of samples was studied by atomic force microscopy (AFM), fractal analysis of the 3D AFM‐images, and statistical analysis of surface roughness parameters. Cube counting method, based on the linear interpolation type, applied for AFM data was used for fractal analysis. The morphology of non‐modified ceramic sample was characterized by the rather big (1–2 μm) grains of α‐Al₂O₃ phase with a habit close to hexagonal drowned in solid solution of t‐ZrO₂ with smooth surface. The pattern surfaces of modified composite content a little amount of elongated prismatic grains with composition close to the phase of СаСеAl₃О₇ as well as hexahedral α‐Al₂O₃‐grains. Fractal dimension, D, as well as height values distribution have been determined for the surfaces of the samples with and without modifying. It can be concluded that the smoothest surface is of the modified samples with Ca⁺² modifier but the most regular one is of the non‐modified samples. A connection was observed between the surface morphology and the physical properties as assessed in previous works. Microsc. Res. Tech. 78:840–846, 2015. © 2015 Wiley Periodicals, Inc.     

Analytical Surface Roughness Parameters of a Theoretical Profile Consisting of Elliptical Arcs

The closed‐form solutions of surface roughness parameters for a theoretical profile consisting of elliptical arcs are presented. Parabolic and simplified approximation methods are commonly used to estimate the surface roughness parameters for such machined surface profiles. The closed‐form solution presented in this study reveals the range of errors of approximation methods for any elliptical arc size. Using both implicit and parametric methods, the closed‐form solutions of three surface roughness parameters, R _t , R _a , and R _q , were derived. Their dimensionless expressions were also studied and a single chart was developed to present the surface roughness parameters. This research provides a guideline on the use of approximate methods. The error is smaller than 1.6% when the ratio of the feed and major semi‐axis of the elliptical arc is smaller than 0.5. The closed‐form expressions developed in this study can be used for the surface roughness modeling in CAD/CAM simulations.     

Investigation of adhesive and frictional behavior of GeSbTe films with AFM/FFM

Frictional force microscope (FFM) was used to investigate the nanoscale frictional behavior of GeSbTe films deposited by magnetron sputtering. The effects of relative humidity, scanning velocity and surface roughness on friction were taken into account. Besides, the frictional behavior of GeSbTe films with different compositions was analyzed. Experimental results show that the coefficient of friction of GeSbTe films is almost independent of scanning velocity, while the frictional force decreases with increasing velocity. Both the relationship of friction vs. normal load and that of friction vs. RMS keep relatively linear, and the coefficient of friction increases with the increase in RMS. The influence of humidity on adhesion between the tip and the GeSb₂Te₄ film is more significant than that between the tip and the Ge₂Sb₂Te₅ film.     

Comparative study of conventional and micro WEDM based on machining of meso/micro Sized Spur Gear

This paper discusses the comparison of micro machining process using conventional and micro wire electrical discharge machining (WEDM) for fabrication of miniaturized components. Seventeen toothed miniaturized spur gear of 3.5 and 1.2 mm outside diameter were fabricated by conventional and micro WEDM respectively. The process parameters for both conventional and micro WEDM were optimized by preliminary experiments and analysis. The gears were investigated for the quality of surface finish and dimensional accuracy which were used as the criteria for the process evaluation. An average surface roughness (R_a) of 50 nm and dimensional accuracy of 0.1–1 μm were achieved in micro WEDM. Whenever applied conventional WEDM for meso/micro fabrication, a R_a surface roughness of 1.8 μm and dimensional accuracy of 2–3 μm were achieved. However, this level of surface roughness and dimensional accuracy are acceptable in many applications of micro engineering. A window of conventional WEDM consisting of low energy discharge parameters is identified for micromachining.     

Precision surface finish of the mold steel PDS5 using an innovative ball burnishing tool embedded with a load cell

A load-cell-embedded burnishing tool has been newly developed and integrated with a machining center, to improve the surface roughness of the PDS5 plastic injection mold steel. Either the rolling-contact type or the sliding-contact type was possible for the developed ball burnishing tool. The characteristic curves of burnishing force vs. surface roughness for the PDS5 plastic injection mold steel using the developed burnishing tool for both the rolling-contact type and the sliding-contact type, have been investigated and constructed, based on the test results. The optimal plane surface burnishing force for the PDS5 plastic injection mold steel was about 420 N for the rolling-contact type and about 470 N for the sliding-contact type, based on the results of experiments. A force compensation strategy that results in the constant optimal normal force for burnishing an inclined surface or a curved surface, has also been proposed to improve the surface roughness of the test objects in this study. The surface roughness of a fine milled inclined surface of 60 degrees can be improved from R_a 3.0 μm on average to R_a 0.08 μm (R_max 0.79 μm) on average using force compensation, whereas the surface roughness was R_a 0.35 μm (R_max 4.56 μm) on average with no force compensation.     

Friction and wear behaviour of aluminium alloy coconut shell char particulate composites

The friction and wear characteristics of Al-11.8%Si alloys containing 10–25 vol.% (3–8 wt.%) dispersions of coconut shell char particles (average size, 125 μm) were evaluated under dry conditions with a pin-on-disc machine. At the lower sliding speed of 0.56 m s^?1, the wear rates and friction coefficients of the composites decreased with increasing volume per cent of dispersed char particles in the aluminium alloy matrix. Scanning electron microscopy observations have revealed the presence of adhering shell char fragments on the worn-out surface of the composites and the average roughness R_a for the worn-out surface of the composite (Al-11.8%Si-8%char) was much less (1.9 μm) than for the worn-out surface of the matrix (3.2 μm). At the higher sliding speed of 5.38 m s^?1, the wear rates increased with increasing volume per cent of dispersed char particles in the matrix and the R_a value for the composite (Al-11.8%Si-8%char) was higher (5.2 μm) than for the matrix (4.6 μm). The worn-out surface of the composites did not show the presence of adhering shell char fragments. The reduction in wear rates and friction coefficients of composites at the lower sliding speed of 0.56 m s^?1 with respect to the matrix alloy wear was attributed to the presence of adhered fragmented bits of shell char on the wearing composite surface.     

Nanowear of Hafnium Diboride Thin Films

Chemical Vapor Deposition-grown HfB₂ films were subjected to nanowear testing at normal loads of 50–500 μN. The material response was investigated by measuring residual wear depths and wear scar roughness and by calculating wear rates and specific energies. Films annealed for 1 h at 800°C showed significant reduction in wear rate and required a higher critical energy for wear, compared to as-deposited HfB₂ films. Analysis of roughness of the worn scars revealed that plowing effect dominates at higher loads (200–500 μN), whereas at lower loads, asperity flattening dominates. The excellent response of annealed HfB₂ films to nanotribological testing demonstrates the potential of these films for applications requiring high wear resistance at the nanoscale.     

A comparison of surface roughness of pipes as measured by two profilometers and atomic force microscopy

The objective of this study was to develop a reliable method for the measurement of pipe surface roughness. Roughness of coated pipe was measured with two linear surface profilers, a Dektak³ST® and a Hommel T 1000, and a Dimension 3000® atomic force microscope (AFM). Arithmetic roughness (R_a), root mean square roughness (R_q), and mean peak‐to‐valley height (R_ZD) were statistically analyzed. Each instrument yielded reliable results, but there were significant differences between the AFM and the other two instruments. The ability of R_ZD to ignore intermediate height data while focusing on extreme height data made it a useful parameter for detecting differences in height that would be the most likely to affect fluid flow in pipes.     

Atomic force microscopy and energy dispersive X‐ray spectrophotometry analysis of reciprocating and continuous rotary nickel‐titanium instruments following root canal retreatment

The aim was to examine the effect of retreatment process on the surface roughness and nickel titanium (NiTi) composition of ProTaper Universal Retreatment (PTUR; consists of 3 files; D1, D2, D3) and WaveOne Gold (WOG) (primary) instruments. Twenty extracted mandibular molar teeth with severe curved (30–40°) mesial roots were selected and divided into two groups (n = 10) based on the instrument used for the removal of the root canal filling. Before and after using the instruments in two canals, they were subjected to atomic force microscopy (AFM) and energy dispersive X‐ray spectrophotometry (EDX) analysis. The EDX analysis data and roughness average (Ra) and root mean square (RMS) values were analyzed statistically using a one‐way analysis of variance and post hoc Tukey's test at the 5% significant level. There was no significant difference between the new and used D1 and D2 PTUR and WOG instruments in terms of the Ni composition (p > .05). The Ti contents of the used D2 and D3 PTUR instruments were lower those of the new instruments (p < .05). In both new and used instruments, PTUR and WOG have no difference in terms of Ra and RMS values. (p > .05). The Ra and RMS values of the PTUR and WOG systems significantly increased after removal of the root canal filling (p < .05). The use of PTUR and WOG instruments for removal of root canal filling in severely curved root canals affected the surface topography of the files. The NiTi composition of the WOG instruments was unaffected by the retreatment process.     

Structural and mechanical properties of (Cr,Ni) N single and gradient layer coatings deposited on mild steel by magnetron sputtering

Ternary single and gradient layer (Cr, Ni) N thin films were deposited on the mild steel substrate by unbalanced magnetron sputtering technique in order to evaluate mechanical properties for machine tools and automotive applications. Microstructure, chemical composition, surface morphology and phase analysis were carried out using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction, respectively. Both single and gradient layer of (Cr, Ni) N coatings show a significant increment in mechanical properties such as hardness, adhesion strength and surface roughness along with the reduction of friction coefficient. Mechanical tests revealed that the hardness of the gradient layer increased up to 3.1 times due to the formation of Cr₂N and Ni phase whereas single layer showed the least friction. Single layer CrNiN layer exhibited 27.2% less surface roughness (R_a) in comparison with gradient layer. High values of surface roughness, hardness, thickness and friction could be correlated with high film-to-substrate adhesion (L_c2) for the gradient layer.