Different Gaussian rough surfaces are considered by varying the auto correlation length. Then, mean summit and actual summit radii based multi asperity contact models are developed. The contact parameters of contact load and contact area are calculated using single asperity contact model results. In high ACL/SL case, at extreme interference, the mean summit and actual summit radii based multi asperity contact models showed 48% and 70% difference in contact area ratio and 30% and 49% difference in contact load ratio respectively. A power law expression is developed to relate the contact load and contact area. A dynamism in elastic-plastic contact states of summits is identified which is discussed in detail too.
Nanoparticle reinforced ternary alloy coatings offer significant advancement in surface engineering applications. We hereby report on a unique system comprising alumina nanoparticle reinforced ternary Ni-P-Mo composite coatings electrodeposited onto HSLA steel substrates. Detailed characterisation showed exceptional enhancement of the mechanical, wear and corrosion resistant properties. An optimised alumina nanoparticle addition (0.3 g/L) drastically improved hardness up to 35.5% and reduced wear rate by around 11.52% compared to pure Ni-P-Mo coatings. Moreover, a significant reduction in corrosion rate in Ni-P-Mo/Al2O3 (0.3 mils/yr) was observed compared to Ni-P-Mo (4.8 mils/yr). However, the introduction of Al2O3 nanoparticles at concentrations exceeding 0.3 g/L seemed to have a detrimental effect on the coating morphology, leading to compromised mechanical strength, wear resistance and corrosion resistant properties.
Binders are critical components in brake pad formulations, significantly influencing their performance, durability, and lifespan. Understanding the interaction between binder variations and other brake pad constituents is essential for optimising braking efficiency and material behaviour. The test rig features a ventilated brake disc driven by a motor and employs a pneumatic system to simulate real-world braking conditions. Brake pad samples are prepared by varying the percentage of binder materials, and an experimental design was formulated using an orthogonal array generated with Taguchi's method. Comprehensive tests, including wear analysis, shear strength, Rockwell hardness, and acetone extraction, are conducted in order to optimise brake pad performance. Results indicated that samples with high phenolic and minimal epoxy content exhibited superior wear resistance, while high epoxy concentrations negatively impacted mechanical properties and density. The results are analysed in MINITAB to determine the optimal binder composition for improved braking efficiency. This study investigates brake pads used in disc brakes and explores the potential for optimising their composition to improve braking efficiency and performance.
Green cutting fluids (GCFs) offer an eco-friendly alternative to synthetic fluids by replacing mineral constituents with sustainable additives. Formulated with coconut oil as base, CAPB as emulsifier, garlic oil as extreme pressure additive, and almond oil as anti-oxidant, GCFs (B01 to B07) exhibit significantly higher viscosities, transitioning to non-Newtonian flow. Viscosity increases 16-27 times at 25 degrees C and 100-121 times at 100 degrees C. B03 and B04 show stable viscosity and excellent high-temperature performance. During tribological tests, B04 reduced friction by 8.6% and wear by 30.17%. Surface-analysis revealed smoother wear-tracks with sulphur-rich layers from garlic oil, confirmed by FESEM/EDAX. Incorporating garlic oil and almond oil resulted in shallow wear scars. For B04, skewness of 0.638 and kurtosis of 3.922 indicate deep valleys with rounder peaks, enhancing lubricant storage and flow GCFs B03 and B04 have shown excellent potential as replacement of mineral cutting fluids ensuring proper heat dissipation and effective wear protection.
This study investigates the influence of groove width on contact characteristics and vibration behaviour in 45 steel-chloroprene rubber friction pairs through numerical simulations and reciprocating friction tests. Results demonstrate that grooves interrupt continuous contact stress distribution via area-loss effects, mitigating stress concentration intensity and vibrational continuity. However, excessive groove width exacerbates over-groove impact phenomena. Numerical analysis reveals that contact stress decreases by 28.6%-49.7% as groove width increases from 400 mu m to 800 mu m, with minimal over-groove impact. Conversely, 1,000-2,000 mu m grooves intensify edge stress concentration and vibration amplitudes due to pronounced over-groove impacts. Experimental measurements confirm 5.9%-11.3% and 17.8%-23.1% increases in absolute average acceleration amplitude and root mean square (RMS) for 1,000-2,000 mu m grooves compared to 800 mu m, validating the degradation mechanism. The medium groove width (800 mu m) achieves an optimal balance between interfacial stress optimisation and vibration suppression, significantly improving interfacial contact behaviour.
To enhance ductile iron performance under harsh conditions, this study investigates the effect of nickel content on laser-clad 3Cr13+2.0wt%B coatings. Results show that adding 1.0 wt% Ni achieves optimal metallurgical bonding and coating quality (average thickness >1.2 mm). The microstructure comprises alpha-Fe, gamma-Fe, (Cr,Fe)7C3, Fe2B, and gamma-(Fe,Ni) phases, with microhardness 4.15 times that of the substrate. Under identical abrasion, the wear rate decreases to 0.135 x 10(-3) g/m, dominated by mild abrasive and oxidative wear. In 3.5% NaCl salt spray tests, the self-corrosion potential increases by 0.052 V, with reduced corrosion current and enhanced impedance, indicating superior corrosion resistance. The addition of 1.0 wt% Ni simultaneously improves coating quality, hardness, wear resistance, and corrosion performance.
Until now, surface treatment methods have been subject to many restrictions because each material has different properties. In addition, the effect of surface treatment has been approached qualitatively rather than quantitatively. This study demonstrates the remarkable improvement in the optical intensity of a matrix upon depositing an ultra-thin film layer, regardless of the morphology, dimension, type, and size. Thus, a new optical energy amplification mechanism, in which the number of photons can be increased, is proposed using a geometrical approach. In particular, the flame chemical vapour deposition used here was achieved within seconds. Moreover, based on the purpose of the process, the reduction of the metal oxide and the deposition of the amorphous carbon could be easily controlled. The powerful optical results were investigated for various material surfaces such as Au-SnO2 nanowires, porous Si substrates, and Al2O3 substrates.
Surface modification strategies are becoming more common to enhance the biological properties of bone implant applications. In this work, multilayer RF-magnetron sputtered Ti/TaN coatings deposited on Ti6Al4V were investigated. Biocompatibility, antibacterial properties, and coating effectiveness were assessed. It was observed that the coating layers played an important role in biocompatibility. Energy-dispersive-spectroscopy confirms the presence of the coating elements. In-vitro tests with HCT-116 cells showed greater viability (survival rate of 96.62%) on the coated sample. Critical loads associated with coating failure were obtained using FESEM micrographs. The cohesive failure began at L-C1 (72.2997 mN) whereas the critical normal load threshold for the thin film coating was obtained at L-C2 (291.3407 mN). The results of this work indicate the viability of deposited coating for implant application.
To improve the surface performance of 304 stainless steel, a Fe55 alloy coating with excellent wear and corrosion resistance was fabricated using high-speed laser cladding with an innovative inside-laser powder feeding method. The effects of laser power, defocus distance, and scanning speed on the coating morphology were studied. SEM and XRD analyses were conducted along with microhardness, wear, and electrochemical corrosion tests. Optimal parameters were identified: 1850 W laser power, 24 m/min scanning speed, +2 mm defocus, 16.8 g/min powder feed rate, and 80% overlap. The resulting coating was smooth, defect-free, had a dilution rate below 5%, and showed improved hardness and corrosion resistance compared to the stainless steel substrate. This efficient and eco-friendly technique has promising potential for advanced surface enhancement applications.
In this study, Ti boride ceramic coatings were prepared on TC4 coating surfaces using boriding post-treatment. The effects of different holding times on the microstructural evolution, mechanical properties and corrosion resistance of laser cladding coatings were investigated. The results showed that the hardness of the coatings was affected by the phase content in various regions of the coatings. The volume fraction of martensite in the coating was significantly reduced after boriding process. The boriding process produced TiB whiskers and a boride layer on the surface of the coating, with a maximum hardness of 1,185 Hv, and the corrosion resistance of the boride layer decreased and then increased with the extension of the holding time. After 10 h of holding, the borides produced on surface were microporous and accelerating corrosion. The density of the boride layer increased after 20 h of holding, and the corrosion resistance was significantly increased.
This study proposes the asymmetrical microtextures added to the surface of the sliding-friction-pair and optimisation of the geometric parameters in asymmetrical microtextures to improve the lubrication efficiency and bearing capacity of the sliding-friction-pair. From the lubrication model of sliding-friction-pair using rectangular asymmetrical micro-structures established, the parameters of the depth and tilting bottom surface in each microtexture are optimised by the genetic algorithm. The result indicates that with the optimal asymmetrical micro-structures distributed by two different regions of the boss and pit region and with the boundary between these two regions to be a curve towards the central area in the direction of the oil film flow, both the hydrodynamic pressure (p) and bearing capacity (W) of the oil film are higher than symmetrical microtextures. In particular, the maximum p and W are strongly increased in comparison with symmetrical microtextures. Thus, the work efficiency of sliding-friction-pair is significantly improved.
A systematic study on AISI 316 L electropolishing (EP) in H3PO4-H2SO4-based electrolytes is presented, aiming to investigate correlations between electrolyte physico-chemical properties and surface finishing and to clarify interfacial phenomena occurring during EP. The effect of electrolyte concentration, [H3PO4]/[H2SO4] ratio and organic additives was considered. Electrical conductivity, density, and viscosity were measured; cyclic voltammetry was run to evaluate EP potential window and plateau current density. Surface finishing was characterised by roughness and brightness measurements; morphology was investigated by optical and electronic microscopy; composition was assessed by energy dispersive X-ray spectroscopy. Best results were obtained in concentrated electrolytes showing lower electrical conductivity, higher viscosity, a wider EP potential window and a lower plateau current density. Lower roughness was obtained when [H3PO4]/[H2SO4] = [H2SO4]/[H3PO4] approximate to 4. Regardless [H3PO4]/[H2SO4] ratio, EP surfaces revealed well-defined crystalline grains, showing different intra-granular microstructure depending on electrolyte composition. Finally, hypotheses on interfacial phenomena governing the process were made.
The present study focuses on in-vitro bio-tribological study of ZTA against AZ31 alloy, in estimating friction and wear rate for long-term sliding distance of 40 km using Ball-on-Disc (B-o-D) tribometer for human hip prosthesis. The bio-lubricants considered for current study includes saline solution, Ringer's solution, distilled water, phosphate buffered saline (PBS) and sesame oil with B-o-D load of 20 N. Sesame oil exhibited least coefficient of friction (CoF) of 0.35 and maximum CoF of 0.42 is obtained for saline solution. Later, wear rate of ZTA is obtained for all these bio-lubricants and found that sesame oil exhibited least wear rate (K) of 8.55 x 10(-6) mm(3)/Nm and maximum (K) of 1.25 x 10(-5) mm(3)/Nm obtained for saline solution. The scanning electron microscope (SEM) micrograph depicted the mechanism behind these wear behaviour under different bio-lubricants, which revealed that, formation of tribo-film under sesame oil bio-lubricant medium could improve longevity of implants.
