Sliding Wear Process Research Articles

Dry sliding wear characterization of squeeze cast LM13/FeCu composite using response surface methodology

Dry sliding wear is one of the predominant factors to be considered while selecting material for automotive and aerospace applications. Researchers have been exploring novel aluminium matrix composites (AMC), which offer minimum wear rate for various tribological applications. In this present work, an attempt has been made to reinforce LM13 aluminium alloy with copper coated steel fibers (10wt.%) using squeeze casting process and to perform dry sliding wear test using pin-on-disc tribometer. Microstructure of cast samples was examined using image analysis system to investigate the dispersion of reinforcement in matrix. Dry sliding wear test was performed by considering factors such as load (10-50 N), sliding velocity (1-5 m∙s-1) and sliding distance (500-2,500 m). Wear test was performed according to the experimental design at room temperature. Three factors and five levels central composite design were used to design the experiments using response surface methodology. Based on the results of the experiments, a regression model was developed to predict the wear rate of composites and checked for its adequacy using significance tests, analyses of variance and confirmation tests. Worn surface of samples was investigated using field emission scanning electron microscope and reported with its mechanisms. Microstructure of cast samples revealed uniform dispersion of reinforcement throughout the matrix. Response surface plots revealed that wear rate of composites increases with increasing load up to 50 N with the velocity 1-5 m∙s-1 and a sliding distance up to 2,500 m. However wear rate decreasesd with increasing velocity at lower loads (up to 20 N) and increased after reaching transition velocity of 2 m∙s-1. Dry sliding wear process parameters were optimised for obtaining minimum wear rate and they were found to be a load of 18.46 N, velocity of 4.11 m∙s-1, sliding distance of 923 m. Worn surface of samples revealed a mild wear at lower loads (up to 30 N), and severe wear was observed at high loads (40-50 N) due to higher level of deformation on the surface.

Speed sintering translucent zirconia for chairside one-visit dental restorations: Optical, mechanical, and wear characteristics

The fabrication of zirconia dental restorations is a time-consuming process due to traditional slow sintering schemes; zirconia (Y-TZP) produced by these conventional routes are predominantly opaque. Novel speed sintering protocols have been developed to meet the demand for time and cost effective chairside CAD/CAM-produced restorations, as well as to control ceramic microstructures for better translucency. Although the speed sintering protocols have already been used to densify dental Y-TZP, the wear properties of these restorations remain elusive. Fast heating and cooling rates, as well as shorter sintering dwell times are known to affect the microstructure and properties of zirconia. Thus, we hypothesize that speed sintered zirconia dental restorations possess distinct wear and physical characteristics relative to their conventionally sintered counterparts. Glazed monolithic molar crowns of translucent Y-TZP (inCoris TZI, Sirona) were fabricated using three distinct sintering profiles: Super-speed (SS, 1580 °C, dwell time 10 min), Speed (S, 1510 °C, dwell time 25 min), and Long-term (LT, 1510 °C, dwell time 120 min). Microstructural, optical and wear properties were investigated. Crowns that were super-speed sintered possessed higher translucency. Areas of mild and severe wear were observed on the zirconia surface in all groups. Micropits in the wear crater were less frequent for the LT group. Groups S and SS exhibited more surface pits, which caused a scratched steatite surface that is associated with a greater volume loss. Tetragonal to monoclinic phase transformation, resulting from the sliding wear process, was present in all three groups. Although all test groups had withstood thermo-mechanical challenges, the presence of hairline cracks emanating from the occlusal wear facets and extending deep into the restoration indicates their susceptibility to fatigue sliding contact fracture.

Wear Resistance of the La62Cu12Ni12Al14 Bulk Metallic Glass Under Dry Friction Conditions

The wear properties of a La62Cu12Ni12Al14 bulk metallic glass (BMG) using sliding wear system under the various normal loads and the annealing conditions have been investigated. Although the La62Cu12Ni12Al14 BMG is brittle during the tensile testing, it exhibits ductile behaviors during the sliding wear process. The SEM and the EDS analyses of the wear tracks and the debris after the sliding wear processes indicate that the wear mechanism is a combination of abrasion, adhesion, and oxidation. It is found that the wear resistance is significantly affected by the normal loads. With the increases in the wear load, the wear loss and the friction coefficient decrease. In addition, it is found that the wear properties are significantly affected by the annealing conditions. Compared with the annealed BMG alloys, the as-cast BMG alloy with a low hardness exhibits good wear resistance, which is attributed to the better ductility during the wear testing.

Evolution of bi-Gaussian surface parameters of silicon-carbide and carbon-graphite discs in a dry sliding wear process

A surface-surface dry sliding wear of silicon-carbide and carbon-graphite discs is performed on a rotational tribological tester. Coefficient of friction (COF) is monitored as a function of time. Samples are measured by a white light interferometer. Four uniform groups, each with two repetitions, are set to different test durations to investigate the evolution of bi-Gaussian surface parameters in a wear process. The results show that the hard sample has a smoothed upper component with time, but a slightly changed lower component due to wear-generated debris. The wear-generated debris, however, introduce deep scratches to the soft sample before its upper component being altered, yielding a sharp lower component. Furthermore, the correlation between bi-Gaussian surface parameters and COF is explored.

Effect of short glass fibre and fillers on friction and wear performance of multi-phased thermoplastic copolyester elastomer composites

The friction and wear performance of multi-phased thermoplastic copolyester elastomer (TCE) composites were studied, using a pin-on-disc (POD) apparatus. The TCE reinforced with short glass fibre (SGF) and filled with various fillers such as polytetrafluoroethylene (PTFE), short carbon fibre (SCF), silicon carbide (SiC), micro/nano alumina (m-Al2O3/n-Al2O3), molybdenum disulphide (MoS2) and perfluoropolyether (PFPE) were slid against a steel counterface. The specific wear rate (Ks) and coefficient of friction (µ) of multi-phased TCE composites were studied for a constant applied load of 40 N. Further, influence of various sliding velocity (0.5, 1.5 and 2.5 m/s) and sliding distance (2000, 4000 and 6000 m) on Ks and µ were discussed. Multi-phased TCE composite with SGF, PTFE, SCF, SiC, m-Al2O3 and MoS2 demonstrated lower Ks, but TCE with SGF, PTFE, SCF, SiC, n-Al2O3 and PFPE exhibited lower µ in the study group. Multi-phase composites reinforced with fibre and various fillers (micro and nanosized) were found to be beneficial in enhancing the friction and wear performance of neat TCE. Further, increase in sliding velocity resulted in increase in Ks and µ, however decrease in Ks and µ was found with increase in sliding distance. Worn surface morphology of multi-phased TCE composites were analysed with the help of scanning electron microscope (SEM) images to understand the probable wear mechanisms involved in dry sliding wear process.

Preparation, properties and wear performance evaluation of epoxy‐palmyra fiber composites

This article presents a parametric analysis of dry sliding wear process undergone by a new class of composite material consisting of epoxy and short palmyra fibers (SPF). It is an attempt to explore the possibility of improving the dry sliding wear resistance of neat epoxy by reinforcing it SPF. Palmyra fiber is an inexpensive, strong, and naturally available fiber derived from the stalks of palmyra leaf. In the present investigation, epoxy‐based composites with different weight proportions of SPF (0, 4, 8, and 12 wt%) are fabricated although the simple hand‐lay‐up route. The tensile, flexural, and micro‐hardness properties of the samples are found out which is followed by a FTIR spectroscopy of the samples. The composite samples are then subjected to wear trials using a pin‐on‐disc test rig as per ASTM G 99‐05 test standards under different operating conditions. The effects of various operational variables on the dry sliding wear behavior of these epoxy composites with and without SPF reinforcement are studied. The design of experiments approach using Taguchi's L16 orthogonal array is used for parametric analysis of the wear process. Significant parameters affecting the wear rate of epoxy are identified. This study revealed that while the fiber content and the sliding velocities have significant influence on the wear arte of the composites, the effects of sliding distance and normal load are ignorable. An optimal parameter setting for minimum specific wear rate is obtained. The morphologies of the worn surfaces are examined by scanning electron microscopy and possible wear mechanisms are identified. POLYM. COMPOS., 39:1827–1834, 2018. © 2016 Society of Plastics Engineers

Investigation of mechanical and tribological properties of tribo‐layer of Ni3Al matrix composites

AbstractThe sliding wear of Ni3Al matrix composites with addition of 1.5 wt.% graphene nanoplates was studied through pin‐on‐disc wear testing. The spontaneous formation of a tribo‐layer produced during sliding wear was found to result in a deviation from Archard scaling and an unexpected high wear resistance that was not based on hardness alone. The tribo‐layer exhibited specific microstructural evolution with significant severe deformation and grain refinement after wear. In the grain refinement area, the accumulation of dislocations and an increase in misorientations were found to lead to strain hardening. For the plastic deformed area, reduction in the dislocation density inside the elongated ultrafine grains reduced strain hardening compared with the grain refinement area. It can be concluded that the deviation from Archard scaling occurred primarily as a result of the microstructural evolution of the tribo‐layer, resulting in the specific performance of mechanical and tribological properties of Ni3Al matrix composites under cyclic sliding wear process. Copyright © 2016 John Wiley & Sons, Ltd.

Recurrence evolvement of brass surface profile in lubricated wear process

This investigation exemplifies how recurrence analysis can be applied to characterize the non-linear dynamic evolution of Cu–30%Zn brass surfaces when sliding under boundary lubricated conditions against AISI 52,100 steel. Roughness profiles of the wear surface of the brass specimen were measured periodically using a specially-designed apparatus to locate the same area of the wear surface. Recurrence plots of these changing surface profiles measured are presented. Two recurrence parameters, average diagonal length (ADL) and correlation dimension (CD), are also computed. The recurrence plots depict conditions before wear testing, during steady-state wear, and after severe wear begins. These sequential plots evolve from a periodic-like pattern, to a partially homogeneous pattern, and then to a disrupted pattern. During wear, the ADL first decreases, stabilizes at a small value, and then finally increases significantly, corresponding, respectively, to a wear-in stage, a steady-wear stage, and a severe wear stage. By contrast, the CD parameter tends toward two dimensions at first, then fluctuates around a large value and then rapidly decreases toward one dimension. The computation of ADL and CD reveals changes in randomness and complexity as the wear surface of the brass specimen passes through three stages. It reveals the non-linear dynamic behavior of the brass-on-steel sliding wear process particularly, but the method may be useful for studies of other metallic wear surface as well.

Influence of Combined Addition of Boron and Strontium on High-Temperature Wear Behavior of A356 Alloy

In the present study, the effect of the combined addition of boron (B) and strontium (Sr) on the high-temperature dry sliding wear behavior of A356 alloy has been investigated using a pin-on-disc wear testing machine attached with a furnace. During wear studies, the effect of alloy composition, normal pressure, sliding speed, and sliding distance on A356 alloy at four temperatures, namely, room temperature and 100, 200, and 300°C, have been investigated. Further, the cast alloys and worn surfaces of A356 alloy with and without B and Sr were characterized by scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) microanalysis. Results indicate that the combined addition of B and Sr to A356 alloy has led to improvements in wear properties. This is due to a change in microstructure, improvement in mechanical properties, and the formation of an oxide layer between the mating surfaces during the sliding wear process.

Wear Mitigation in Cast Magnesium Alloy through Flyash Reinforced Friction Stir Surface Compositing

An attempt is made to mitigate wear in cast magnesium alloy by incorporating flyash reinforcement on the surface through friction stir processing. Wear resistance is evaluated using pin-on-disc wear testing. Effect of dry sliding wear process parameters such as speed, time and distance were studied by using design of experiments. Empirical relationships were established between the process parameters and wear resistance of base metal as well as surface composite. Further, wear map is constructed using graphical optimization technique, which can be used to predict the lower and upper bound of wear rate for the both base metal and friction stir processed surface composites under dry sliding condition.

Influence of Subsurface Micro/Nano-Structural Evolution on Macroscopic Tribological Behavior of Ni3Al Matrix Composites

The relationship between macroscopic tribological behavior and subsurface micro/nano-structural evolution needs to be studied in detail. We report here the results of dry sliding tribological tests of Ni3Al matrix composites with 1.5 wt% graphene nanoplatelets (GNPs) under different loads. We found that the friction coefficient decreased with increasing load, while the wear rate showed a downward trend after an initial increase. During the sliding wear process, severe plastic deformation and an accumulation of friction heat caused the formation of an ultrafine layer (UL) and a matrix refinement layer (MRL). The UL contributes to the reduction of friction coefficient and wear rate, and the MRL contributes to the improvement of wear resistance. In addition, GNPs accumulating in the UL tend to be parallel to the worn surface, causing a reduction in friction and an increase in wear resistance for the properties of easily shearing off and high tensile strength. The hardness and elastic modulus of the UL and MRL increased due to grain refinement and the accumulation of GNPs in these layers. The effective hardness of the multilayer was approximately 7.2 GPa.

Tribological characteristics and tribo-chemical mechanisms of Al–Mg–Ti–B coatings under water–glycol lubrication

In this work, the tribological characteristics and tribo-chemical mechanisms of the water–glycol lubricated Al–Mg–Ti–B coatings under various normal loads were studied by pin-on-disk unidirectional sliding test, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). The water–glycol lubricated Al–Mg–Ti–B coatings showed a steady-state friction coefficient as low as 0.02 and this value was not influenced by the applied normal loads. As the normal loads increased, the friction coefficients of the Al–Mg–Ti–B coatings decreased more rapidly. Examination of the wear tracks of water–glycol lubricated Al–Mg–Ti–B coatings by SEM and EDX shows that the sliding wear process was dominated by a polishing effect. XPS results indicate that significant surface boron oxidation of Al–Mg–Ti–B coatings occurred during sliding in a water–glycol lubricated environment; such effect was more pronounced at higher normal loads. However, there is no clear evidence of the presence of boric acid in XPS spectra at all applied normal loads. This is thought to be due to the unstable nature of boric acid and in situ surface characterization of the water–glycol lubricated Al–Mg–Ti–B coatings needs to be done to clarify this issue.

Multi-response optimization of tribological characteristics of aluminum MMCs using PCA

Purpose – Since, wear is the one of the most commonly encountered industrial problems leading to frequent replacement of components there is a need to develop metal matrix composites (MMCs) for achieving better wear properties. The purpose of this paper is to fabricate aluminum MMCs to improve the dry sliding wear characteristics. An effective multi-response optimization approach called the principal component analysis (PCA) was used to identify the sets of optimal parameters in dry sliding wear process. Design/methodology/approach – The present work investigates the dry sliding wear behavior of graphite reinforced aluminum composites produced by the molten metal mixing method by means of a pin-on-disc type wear set up. Dry sliding wear tests were carried on graphite reinforced MMCs and its matrix alloy sliding against a steel counter face. Different contact stress, reinforcement percentage, sliding distance and sliding velocity were selected as the control variables and the response selected was wear volume loss (WVL) and coefficient of friction (COF) to evaluate the dry sliding performance. An L25 orthogonal array was employed for the experimental design. Optimization of dry sliding performance of the graphite reinforced MMCs was performed using PCA. Findings – Based on the PCA, the optimum level parameters for overall principal component (PC) of WVL and COF have been identified. Moreover, analysis of variance was performed to know the impact of individual factors on overall PC of WVL and COF. The results indicated that the reinforcement percentage was found to be most effective factor among the other control parameters on dry sliding wear followed by sliding distance, sliding velocity and contact stress. Finally the wear surface morphology of the composites has been investigated using scanning electron microscopy. Practical implications – Various manufacturing techniques are available for processing of MMCs. Each technique has its own advantages and disadvantages. In particular, some techniques are significantly expensive compared to others. Generally the manufacturer prefers the low cost technique. Therefore stir casting technique which was used in this paper for manufacturing of Aluminum MMCs is the best alternative for processing of MMCs in the present commercial sectors. Since the most important criteria of a dry sliding wear behavior is to provide lower WVL and COF, this study has intended to prove the application of PCA technique for solving multi objective optimization problem in wear applications like piston rings, piston rods, cylinder heads and brake rotors, etc. Originality/value – Application of multi-response optimization technique for evaluation of tribological characteristics for Aluminum MMCs made up of graphite particulates is a first-of-its-kind approach in literature. Hence PCA method can be successfully used for multi-response optimization of dry sliding wear process.

Fractal characterization of the friction forces of a graded ceramic tool material

The sliding friction and wear tests were performed with a pin-on-disc system. The time series values of the friction forces were collected. The fractal characterization of the friction forces of the graded ceramic tool material and Inconel 718 pair was investigated in the sliding wear process, according to the calculation method of correlation dimension. The worn surfaces of the friction pairs were characterized by a scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS). And the sliding wear mechanisms of the graded material and Inconel 718 were also analyzed. The results showed that the time series values of the friction forces had an apparent fractal characteristic. The fractal dimension of the friction forces decreased gradually in the sliding wear process. The sliding wear mechanisms of the ceramic disc in the sliding wear tests were adhesive wear, abrasive wear, and chipping, while those of the Inconel 718 pin were plastic deformation, abrasive wear and adhesive wear, as a result of the combined effect of high temperature and high stress in the contact surface.

Dry sliding wear behavior of SS316L composites containing h-BN and MoS2 solid lubricants

Mechanical properties and wear behavior of stainless steel supplemented with different solid lubricants were investigated. Hexagonal boron nitride (h-BN), molybdenum disulfide (MoS2), and a mixture of h-BN/MoS2 embedded in 316L stainless steels (SS316L/h-BN, SS316L/MoS2 and SS316L/h-BN/MoS2) were prepared by powder metallurgy method. Various solid lubricant contents (10, 15 and 20vol%) were mixed with 316L stainless steel powders and then sintered at 1200°C in H2 atmosphere for 60min. Dry sliding wear behavior of the composites was investigated using a pin-on-disc test rig at sliding speeds of 0.1 and 0.2m/s and an applied load of 3N. The experimental results showed that small boride phase and h-BN powder occupied the pores in the microstructure of the SS316L/h-BN composite, whereas the MoS2 second phase occupied the pores of the sintered 316L matrix in the microstructure of the SS316L/MoS2 composite. The addition of h-BN decreased the sintered density and hardness, whereas that of MoS2 produced the opposite effect. The results showed that the MoS2 composite had higher wear resistance than the h-BN composite, but the h-BN composite yielded better friction reduction. Furthermore, the addition of an h-BN/MoS2 mixture could promote the hardness and wear resistance of the composites. The incorporation of h-BN and MoS2 had the potential to provide friction reduction in SS316L composites as compared with sintered 316L stainless steel. The dry sliding wear process of stainless steel composites with added h-BN, MoS2 and h-BN/MoS2 involved adhesive wear, abrasive wear, oxidative wear and delamination wear mechanisms of the compacted layer.

Taguchi Grey Relational Analysis of Dry Sliding Wear Behaviour of Annealed AA7075-TiC Metal Matrix Composites

The optimization of dry sliding wear process parameters of in-situ aluminium based metal matrix composites to obtain multiple objectives to minimize wear rate, specific wear rate, co-efficient of friction and maximize wear resistance was attempted by Taguchi Grey Relational Analysis. Moreover to identify the significance of the parameters, a statistical analysis was performed using analysis of variance. Based on the analysis, the sliding speed was identified as the major contributor with 71.41% followed by percentage of reinforcement with 8.13% and other parameters load and sliding distance are found to be insignificant. The optimum parameters identified by the Grey Relational Analysis are verified through experimental confirmation test.

A New Analysis Method of the Dry Sliding Wear Process Based on the Low Cycle Fatigue Theory and the Finite Element Method

In the present work, a combination of a dynamic explicit finite element model and the low cycle fatigue theory is used to simulate the steady-state abrasive wear occurring between an as-cast eutectoid steel and a carbide-tungsten disk. While the low cycle fatigue theory has been used to model wear in softer non-ferrous alloys, this work shows its applicability and accuracy for use in harder alloys, such as the eutectoid steel used in this research which is strengthened with added chromium. The novelty of this work lies in calculating the Manson-Coffin relation constants from a coupled finite element model with experimental tests instead of the previously used Slip line method. The D Manson-Coffin constant, obtained around 2, is in agreement with previous works given in the literature showing that the low cycle fatigue is a general wear mechanism in the steady-state wear of the alloy tested in this work.

Evaluation of the wear properties of dual two-phase Ni3Al/Ni3V intermetallic alloys

Two-phase Ni3Al3V intermetallic alloys with and without carbon addition, composed of geometrically closed-packed (GCP) structures of Ni3Al (L12) and Ni3V (D022), were investigated for dry sliding wear against a G5 disc (WC carbides with a hardness of 1350 HV) at 298K and 573K by using a pin-on-disc type configuration. The dry sliding wear of a commercial Inconel 718 was also studied under the same experimental conditions for comparison. The wear mass loss measured for the Ni3Al3V intermetallic alloys increased with increasing sliding distance. In the dry wear test at 298K, the 0.1 C intermetallic alloy showed the lowest wear mass loss, followed by the 0 C alloy and then the 0.5 C alloy. At 573K, the 0.5 C alloy showed the smallest wear mass loss, followed by the 0.1 C alloy and then the 0 C alloy. All three intermetallic alloys showed better wear resistance compared to Inconel 718 at both test temperatures. The good wear resistance of the Ni3Al/Ni3V two-phase intermetallic alloys was attributed to the combination of the positive temperature dependence of the flow strength and the strong friction-induced work hardening during the dry sliding wear process.

Micro-characterization of macro-sliding wear for steel

Abstract The wear behaviours of 65Mn and 40CrMnSiW steels were investigated by subjecting them to nanoscratch, nanoindentation, and dry sliding wear processes. A simple modified equation for calculating nanoscratch true wear volumes is developed, i.e. the true volumes are closely related to the elastic recovery angle which can be given easily. When comparing the nanoscratch phenomena with macro sliding wear, it was found that the micromechanism of the macro wear was similar to those of nanoscratching. The nanoscratching and the macro sliding wear testing represented the procedures for evaluation of single-asperity and multi-asperity contact behaviours of abrasive wear, respectively. In addition, to compare wear resistance properties of steels, the mean wear rate increased with decreases in ratio of the hardness H and the reduced modulus E r in turn, namely, the value of H / E r can help to assess the wear resistance of steels in some degree.

Microstructural characteristics of SiC-B4C reinforced laser alloying composite coatings

Abstract A hard SiC-B4C reinforced composite coating was fabricated by laser alloying of SiC-B4C+Al-Sn-Mo-Y2O3 mixed powders on a Ti-3Al-2V alloy. Al-Sn-Mo mixed powders were first used in the laser alloying technique to improve the wear resistance of titanium alloys. Proper selection of the laser alloying process parameters allows us to obtain a composite coating with a metallurgical combination with substrate. Under the action of Mo, fine particles with high microhardness were produced in the coating matrix and also hindered the formation of adhesion patches and deep plowing grooves during the sliding wear process, leading to the improvement of wear resistance of a titanium alloy substrate surface.