Papers by Keyword: Sliding Wear

Abstract: The vast applications of NiTi-based alloys in engineering and biomedicals follow their good mechanical and excellent corrosion properties. In most applications, these materials are exposed to aggressive conditions, leading to surface deterioration due to the combined actions of mechanical and chemical activities. This synergistic interaction under sliding wear contact and applied electrochemical potential informed the choice for this study. The experimental investigation involved coupling a linear reciprocating ball-on-plate tribometer to an electrochemical potentiostat cell of 3-electrode configuration. This allowed the reciprocating sliding of a counter material (alumina ball – Al₂O₃) against the exposed surface area, 2 cm² of NiTiNOL60 alloy fully submerged in a 0.05 M NaOH medium. The unexposed surfaces were coated with a plasti-Dip adhesive to create an additional layer that ensures the isolation/ non-interference of the surfaces during electrochemical measurements while protecting the underlying material from corrosion attacks. The tribo-electrochemical actions at room temperature created a wear groove and deformations along the stroke length. Surface characterization techniques such as optical microscope, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and stylus profilometry were used to examine the resulting wear tracks. Our findings revealed surface and microstructural deformations alongside the various wear mechanisms, including abrasion, adhesion, localized corrosion, and plastic deformation. While the mechanical action due to the sliding contact resulted in grain elongation perpendicular to the sliding direction, the electrochemical activity at the anodic and cathodic polarizations showed that passive film dissolution is dependent on the corrosion potential. The continuous reciprocating sliding promoted accelerated corrosion and the material wear rate at higher loading conditions. This increased the depassivation rate and the oxidation concentration within the wear track, thereby promoting localized corrosion (pits, cracks and crevices) at the sliding interface. The findings from our analysis depict that both mechanical and electrochemical interactions strongly influence the tribocorrosion wear mechanisms of NiTiNOL60 alloy in a corrosive medium.

Abstract: Co-28Cr-6Mo alloy (ASTM F75) is widely used in different biomedical applications (dental devices, orthopedic implants, etc.). Casting and metal forming are the two conventional technologies for the fabrication of this alloy. Recently, additive manufacturing has also been adopted. Due to the peculiarities of this technological process, 3D-printed alloys differ from traditionally manufactured alloys in their structure and properties. In the present work, the features of selective laser melted Co-28Cr-6Mo alloy were studied in comparison with its wrought analogue. The study included microstructural characterization (optical and electron scanning microscopy), nanoindentation, and tribological testing. It was shown that the SLM alloy featured the “fish-scale” structure, characteristic of additively fabricated alloys. This structure was composed of fine columnar dendrites. SLM Co-28Cr-6Mo was found equivalent or superior to the wrought alloy in terms of properties, such as hardness, elastic modulus and tribological behavior that makes SLM Co-28Cr-6Mo a promising candidate for implant applications.

Abstract: The awareness on sustainability of the environment among the researchers leads to the exploration of natural fiber composite materials. Hybridization of synthetic fiber and natural fiber is one of the potential strategies to enhance the mechanical properties as well as the degradability of such composite materials. However, less information concerning the optimization of tribological properties of this hybrid composite is available in literature. The aim of this study is to propose a statistical model to predict and optimize wear and coefficient of friction of kenaf/carbon reinforced epoxy composite. The value of parameters; load and sliding velocity ranges from 10 to 30 N and 20.9 to 52.3 m/s, respectively, are used to assess wear and coefficient of friction (COF) of different stacking sequences using the Analysis of Variance (ANOVA). The tribological test was conducted using a pin-on-disc tribometer. Multifactorial design analysis was employed to optimize the test control variables. It was found that, the optimized factors that affects the coefficient of friction and wear is at load 30 N and sliding velocity of 52.36 m/s. The proposed statistical models for wear and COF have 99.5% and 97.6% reliability, respectively. The generated equation models are bounded within the wear test control factors and ranges. The outcome from this study will be very useful for main parameter prediction for an optimized wear and COF.

Abstract: The effects of temperature on the friction and wear properties of GCr15 were studied by using a RETC multifunctional friction and wear testing machine. The microstructure characterization of the worn surface of the experimental steel was studied by means of metallographic microscope (OM), white light interferometer, secondary electron image (SEI) and back scattered electron image (BEI).The results show that the wear resistance of GCr15 bearing steel at room temperature is better than that at 100°C, 150°C and 200°C. At room temperature, the main wear forms of GCr15 are adhesion wear and fatigue wear. However, at 100°C, 150°C, 200°C, the friction coefficient and oxidation degree in the wear zone first increase and then decrease with the increase of temperature, and the wear form is mainly oxidized wear, accompanied by abrasive wear.

Abstract: Contact modeling could be widely used for different machine elements normal contact pressure calculations and wear simulations. However, classical contact models as for example Hertz contact models have many assumptions (contact bodies are elastic, the contact between bodies is ellipse-shaped, contact is frictionless and non-conforming). In conditions, when analytical calculations cannot be performed and experimental research is economically inexpedient, numerical methods have been applied for solving such engineering tasks. Contact stiffness parameters appear to be one of the most influential factors during finite element modeling of contact. Contact stiffness factors are usually selected according to finite element analysis software recommendations. More precise analysis of contact stiffness parameters is often required for finite element modeling of contact.

Abstract: The multilayered AlCrN coating physical vapour deposited (PVD) over the stainless steel (SS) substrate was studied. Raman spectroscopy was used to determine the resistance of the coating under high temperature oxidative conditions (25–800 °C). Static oxidation tests of the AlCrN PVD coating mainly leads to the formation of Cr₂O₃ at temperatures up to 800 °C. The results of the sliding tests indicate the development of oxides layers in the wear tracks on the surface of AlCrN PVD coated samples at the room temperature, which is critically dependant on the sliding speed against Si₃N₄ counter balls. The maximum reliable sliding speeds against Si₃N₄ counter balls under applied normal load of 3 N at 20, 300/500 and 800 °C was determined to be 0.486, 0.162 and 0.054 m·s^-1, respectively.

Abstract: The present study includes a detailed analysis of titanium based composite foam developed by powder metallurgy route and to understand the role of process parameters and the particle size of the space holder (cenosphere) on the kinetics and mechanism of wear. Cenosphere of varying particle size (<150 μm; 150-212 μm; > 212 μm) were mixed with titanium in a ratio of 1:3, compacted at 100 MPa and sintered at 1000°C and 1200°C for a period of 2,4 & 6 hrs in each temperature. The kinetics of wear and frictional coefficient of sintered composites were evaluated by reciprocating wear testing machine against diamond indenter at applied load of 10 N. The mechanism of wear was studied by a detailed analysis of the post wear microstructure. The composite foam with cenosphere particle size in the range of 150-212 μm showed minimum wear rate. The mechanism of wear was found to be a combination of adhesive and abrasive.

Abstract: The paper presents the results of a SEM/EDS and XPS study of changing of chemical and phase composition of the friction surfaces Fe-Mn-C-B-Si-Ni-Cr hardfacing coatings depend on depth. The tribological examination was conducted in a pin-on disc system with unitary pressure of 10 MPa under dry friction conditions. A scanning electron microscope SEM/EDS as well as X-Ray photoelectron spectroscopy (XPS) were used to examine the structures on the friction surface and depend on depth 5, 10, 15, 20, 50, 100, 200, 6000 nm. The presence of compounds such as oxides (B₂O₃, SiO₂, Cr₂O₃), carbides (Fe₃C, Cr₇C₃), borides (FeB, Fe₂B).

Abstract: The present research focuses onto sliding wear of novel plasma transferred arc welded (PTAW) hardfacing with the stainless steel (DIN X3CrNiMo18-13-3) matrix, reinforced with WC/W₂C, under the room and elevated temperature. The hardfacing was produced, applying the optimized set of parameters (current – 55 A, reciprocating speed – 1.0 mm/s, oscillation frequency – 0.6 Hz). The average reinforcement content was 29.3 ± 4.0 vol %. The reinforcement consisted of W₂C and WC, while M₇C₃- and M₂₃C₆-type (M = Fe, Cr, Mo, W) carbides were the main phases in the matrix. Universal hardness and Young’s modulus were approximately 5.3 and 1.9 times higher, than those of the reference steel (DIN X2CrNiMo18-14-3). The sliding wear of the hardfacing was 4.9 times lower under 20 °C and 3.1 times lower under 300 °C, but 1.8 times higher under 500 °C than the wear of the reference steel. Galling was the wear mechanism of the hardfacing under 20 °C, scoring – under 300 °C and combination of scoring and binder extrusion – under 500 °C

Abstract: In this study, attempt has been made to investigate the effect of SiC particles on the friction and wear properties of Ni/SiC composites manufactured by electrodeposition, especially for the composites with high-temperature treatment.For this purpose, α-Al₂O₃ was coated on the surfaces of SiC particles by sol-gel technology to inhibit interfacial reaction of SiC and nickel at high temperature. Both of the Ni/α-Al₂O₃-coated SiC (Ni/CS_p) and Ni/uncoated SiC (Ni/UCS_p) composites were treated at 600 °C to study the resulting wear behaviour. The results indicated that with heat treatment at 600 °C, the Ni/CS_p composite had better tribological properties than the Ni/UCS_p composite. It was proved that the uncoated SiC particles have reacted completely with nickel leaving many defects, while the coated SiC particles still remained in the Ni/CS_p composite hardening the nickel matrix and supporting the counterpart, thus improving the wear resistance of Ni/CS_p composite with relatively low friction coefficient and wear mass loss compared to the Ni/UCS_p composite.