Wear Rate Of Disc Research Articles

A Novel Approach by Spark Plasma Sintering to the Improvement of Mechanical Properties of Titanium Carbonitride-Reinforced Alumina Ceramics.

Ti(C,N)-reinforced alumina-zirconia composites with different ratios of C to N in titanium carbonitride solid solutions, such as Ti(C0.3,N0.7) (C:N = 30:70) and Ti(C0.5,N0.5) (C:N = 50:50), were tested to improve their mechanical properties. Spark plasma sintering (SPS) with temperatures ranging from 1600 °C to 1675 °C and pressureless sintering (PS) with a higher temperature of 1720 °C were used to compare results. The following mechanical and physical properties were determined: Vickers hardness, Young’s modulus, apparent density, wear resistance, and fracture toughness. A composite with the addition of Ti(C0.5,N0.5)n nanopowder exhibited the highest Vickers hardness of over 19.0 GPa, and its fracture toughness was at 5.0 Mpa·m1/2. A composite with the Ti(C0.3,N0.7) phase was found to have lower values of Vickers hardness (by about 10%), friction coefficient, and specific wear rate of disc (Wsd) compared to the composite with the addition of Ti(C0.5,N0.5). The Vickers hardness values slightly decreased (from 5% to 10%) with increasing sintering temperature. The mechanical properties of the samples sintered using PS were lower than those of the samples that were spark plasma sintered. This research on alumina–zirconia composites with different ratios of C to N in titanium carbonitride solid solution Ti(C,N), sintered using an unconventional SPS method, reveals the effect of C/N ratios on improving mechanical properties of tested composites. X-ray analysis of the phase composition and an observation of the microstructure was carried out.

Влияние коэффициента взаимного перекрытия на интенсивность изнашивания тормозных накладок дискового тормоза

Влияние коэффициента взаимного перекрытия на интенсивность изнашивания тормозных накладок дискового тормоза

AlSi ALLOYS FOR MAGNETRON DEPOSITION OF THE COATINGS ON CAR EXHAUST MUFFERS – FORECAST OF TECHNOLOGICAL WEAR

In the production of car exhaust system parts, for protection against corrosion and high-temperature oxidation, alumina and AlSi alloy hot-dip coatings are currently especially effective. The authors of this study are conducting investigations into the application of AlSi alloys made by the traditional casting technology to the fabrication of AlSi PVD coatings by the magnetron sputtering method. For the purposes of the present study, three discs of AlSi alloys were subjected to magnetron sputtering. The assessment of the wear of the discs was made by microscopic observations, by mapping the geometric features and roughness of the disc surface with a profilometer, and by making the statistical analysis of the results by the bootstrap method. A similar degree of wear of discs made of all the examined alloys, expressed as the depth of losses, was shown. It was also fund that the surface of discs of alloys with a higher silicon content was characterized by a lower roughness compared to the AlSi7 alloys. The wear rate of discs in the PVD process was estimated at approx. 150 m/h.

Tribological Behaviors of 3D Needled C/C–SiC and FeSi75 Modified C/C–SiC Brake Pair

Tribological properties of FeSi75 modified C/C–SiC and C/C–SiC mutual-mated disks (FS–SI) were investigated; the results indicated that FS–SI can combine the advantages of FeSi75 modified C/C–SiC self-mated disks (FS–FS) and C/C–SiC self-mated disks (SI–SI). In dry condition, the average kinetic coefficient of friction (µ) of FS–SI is 0.55 ± 0.02, and it is about 83% higher than that of FS–FS. The average wear rate of disks in FS–SI is about 0.57 µm time−1, which is much lower than that of SI–SI (~1.46 µm time−1) and slightly higher than that of FS–FS (~ 0.36 µm time−1). It seems that FS–SI can well meet the requirements of brake applications. Moreover, tribological properties of FS–FS and FS–SI in wet condition were firstly reported, and the µ of FS–FS is higher than that in dry condition. Lubrication effect of water just resulted in a small decrease in the µ of FS–SI in the pre-up braking stage, and it will recover rapidly in the later stage.

Influence of temperature and concentration on tribological properties of silicon nitride in glycerol aqueous solution

Friction and wear behaviors of self-mated Si3N4 in glycerol aqueous were investigated by varying the temperature (30°C, 50°C, and 70°C) and concentration (pure water, 5vol%, 20vol%, and 50vol%) of glycerol aqueous solution. Friction tests were conducted on a ball-on-disk apparatus. Normal load and sliding velocity were fixed at 30N and 0.5m/s, separately. After each tests, friction coefficients and wear rates were measured to evaluate friction and wear behavior. The results showed that the period of running-in process reduces with the increase of concentration and decrease of temperature. Increase of temperature could intensify wear behavior, and when concentration is larger than 20vol%, wear rate of glycerol aqueous solution is one order less than that of pure water. Our findings could also guide for the use of glycerol aqueous solution as lubricant at different temperature. At 30°C, the higher the concentration was, the smaller wear volume and total wear rate were. However, at 50°C and 70°C, total wear rates of disk were the largest when concentration is 5vol%, a concentration of glycerol larger than 20vol% must be added into water to reduce the wear rate. Wear regimes at different conditions were also given in this paper based on lubrication state number.

On the model for identification of wear law parameters of viscoelastic materials based on ball-on-disk wear tests

An analytical model of contact interaction between spherical indenter and rotating disk of viscoelastic material (ball-on-disk configuration) is considered. The numerical analysis for influence of load–speed regime on wear rate of disk is carried out. It is shown that adequate choice of contact interaction model which takes into account rheological behavior of the disk material is important in identification of wear law parameters based on the testing results.

Sliding Wear Properties of Self‐Mated Yttria‐Stabilized Tetragonal Zirconia Ceramics in Cryogenic Environment

The objective of the present work is to investigate the friction and wear of self‐mated ZrO2 ceramics in a cryogenic environment. Using a specially designed high‐speed cryo‐tribometer, fine‐grained yttria‐stabilized tetragonal ZrO2 polycrystals (Y‐TZP) were worn at varying loads (5–15 N) with sliding speed of 1.1 m/s in a cryogenic environment (liquid nitrogen, LN2). For comparison, the sliding tests were also conducted under selected operating conditions on self‐mated Y‐TZP under ambient conditions (room temperature (RT)), primarily to understand the difference in wear mechanisms for a given sliding condition. With these planned experiments, it was attempted to answer some important issues: (a) Can sliding in LN2 reduce the coefficient of friction (COF) of self‐mated ZrO2? (b) Does t‐ZrO2 transformation occur in a cryogenic environment and if it occurs, how does it affect the fracture behavior? (c) How does the mechanism of wear change from RT to LN2 temperature? In our experiments, high COF (0.35–0.75) and high wear rate of disks 10−4–10−6 mm3·(N·m)−1 have been measured under the selected tribological testing conditions. Interestingly, X‐ray diffraction analysis revealed the presence of o‐ZrO2 after sliding in a cryogenic environment, while no change in phase assemblage was recorded after sliding under identical conditions at RT. An important observation has been that severe plastic deformation (wider and deeper grooves) at RT and microcracking (“fish scale” pattern)‐induced spalling of a damaged layer in an LN2 environment are the dominant wear mechanisms, respectively.

A mild oxidation model valid for discontinuous contacts in sliding wear tests: role of contact frequency

The volumetric wear rate of PVD TiN-coated disks sliding against corundum balls has been investigated as a function of wear track diameter (16–50 mm), sliding speed (0.06–1.41 m/s) and contact frequency (1–16 Hz) in uni-directional ball-on-disk sliding wear tests. The wear rate of the disk material is shown to depend not only on the usual test parameters, namely sliding speed and contact load, but also on the contact frequency. In order to take this last parameter into account, a modification to Quinn’s mild oxidation wear model originally developed for the continuous contact of a pin against a disk, is proposed to account for discontinuous sliding contacts. As a result, a low dispersion in the wear test results is obtained in contrast with disk wear data from pin-on-disk and ball-on-disk tests reported in the literature. By including contact frequency in addition to load and speed, as an independent factor, modeling of the mild oxidation wear of materials in discontinuous sliding contacts has been achieved.

Tribological properties of self-lubricating CMC/Al 2 O 3 pairs at high temperature in air

Three different self-lubricating ceramic matrix composites (CMCs) were fabricated by hot-pressed sintering. They are: Al2O3-50CaF2, Al2O3-20Ag20CaF2, and Al2O3-10Ag20CaF2. Tribological tests were performed at temperatures ranging from 20°C to 800°C in air using a pin-on-disk tester. The experimental results show that the addition of the solid lubricants CaF2 and Ag can evidently reduce the friction coefficients of alumina between 200°C and 650°C but not at room temperature and the wear rate of disks and pins at elevated temperature. The improvements in the friction and wear properties of CMC were due to the formation of a well-covered solid lubricating film. However, breakdown of the lubricating films at 800°C resulted in high friction and wear.

Tribological properties of carbon nitride overcoat for thin-film magnetic rigid disks

For the purpose of developing a new protective overcoat through the understanding of friction and wear mechanism at nanoscale, two types of commercial carbon coatings and CN x coatings, deposited by ion beam assisted deposition (IBAD) on magnetic media (1.8″ magnetic rigid disk) were tested against Si 3N 4 using pin-on-disk test equipment. Wear surfaces were analyzed with AFM to measure the wear rate of the disks. it was observed that wear and friction of both carbon- and carbon nitride-coated disks was localized in the surface texture (bumps). A method of calculation of wear volume and wear rate for this case has been proposed. Wear rate of the carbon nitride-coated disk was found to be about 10-times lower than that of the disk coated with commercial carbon (90%C–10%Si) of the same thickness. Carbon nitride coating also provided about 3–30-times longer life than commercial carbon coatings. The friction coefficient observed for the CN x coating was lower than that of carbon coatings observed at the same load.

Wear behaviour of plasma-sprayed partially stabilized zirconia on a steel substrate

In this experimental investigation, various layers of partially stabilized zirconia (PSZ) coated on steel by plasma spraying were studied to gain a better understanding of the tribological behaviour of PSZ under the conditions of dry contact in a reciprocating motion at a temperature of 200 °C, which represents the severe operating conditions of friction pairs, such as cylinder liner-piston ring. The parameters investigated in relation to the wear behaviour were the thickness of the coating, oscillating frequency, sliding cycle and applied load. To identify the wear mechanism, X-ray diffraction, scanning electron microscopy and optical microscopy were used. In comparison with a steel-steel pair, PSZ coating-steel and PSZ coating-PSZ coating pairs exhibit far better wear characteristics and, therefore, the distinct possibility of applying a plasma-sprayed PSZ coating as a cylinder liner has been confirmed. The oscillating frequency and applied load conversely affect the wear rate of disc. The recommended coating thickness was found to be in the range 180–300 μm to ensure good anti-wear behaviour without the expense of high coating cost.