Papers by Keyword: Wear Mechanisms

Abstract: In the scope of this study, quenched and tempered H13 steel samples were subjected to conventional (CN) and low temperature (LTN) gas nitriding in a fluidized bed reactor. Structural examinations revealed that surfaces of the CN sample were covered with about 1-2 µm thick compound layer (CL) with an underlying ~30 µm thick nitrogen diffusion zone (NDZ), while outer surface of the LTN sample consisted of ~25 µm thick NDZ. The surface hardness values were measured as 1320 HV_0.1 for LTN sample and 1220 HV_0.1 for CN sample. Under impact sliding conditions, wear mechanisms of the CN and LTN samples were determined as “oxidation + fatigue” at RT and “plastic deformation” at 600 °C. As a general trend CN sample exhibited better impact sliding wear resistance compared to LTN sample both at RT and 600 °C.

Abstract: The wear behavior of powder metallurgical Ti-47Al-2Cr-0.2Mo alloy prepared by pre-alloyed powders was investigated using pin-on-disk wear tests in different environments, viz, argon, 4% hydrogen in nitrogen, air and oxygen. The disk material was sinter-hot isostatically pressed, yttria-stabilized zirconia. Lower wear rates were found for the TiAl pins in oxygen-free environments, indicating that oxygen play a key role in the wear rate. In contrast, the presence of molecular hydrogen and moisture have nearly no effect. A combination of X-ray diffraction and energy dispersive X-ray spectroscopy indicated that the abrasive particles present mainly consisted of the zirconia. In addition, zirconia particles were embedded in the worn tips of the TiAl pins and mixed into the tribolayers. The high stress and high contact temperature at the wear surface made the zirconia disk undergo a phase transformation during the dry sliding wear, accompanied by grain pullout, surface uplifting and microcracking. The hard tribolayer with embedded zirconia particles provides some protection against further wear of the TiAl pin. The highly localized, repetitive shear stress during the wear tests may bring about amorphous TiAl in the wear debris. The main wear mechanisms were abrasive wear of two-body and three-body, some delamination and plastic deformation.

Abstract: This work is focused on the damage and wear mechanisms of phosphate conversion coatings which were deposited onto steel substrates by a wet-chemical process. For studying the damage mechanism, sets of multiple scratches were performed. Scratch tests along with SEM micrographs revealed the early damage mechanisms as well as the running-in friction and wear behaviour of phosphate conversion coatings. The deeper understanding allows to increase tribological performance in terms of controlled friction and wear resistance of technical components. This way, promising measures in reduction of seizing and increase of lifetime for such components could be developed.

Abstract: Materials added to the matrix help improving operating properties of a composite. In the last few years, nanofiller /polymer composite have been widely investigated because of their outstanding multifunctional properties. In order to improve the erosive wear resistance of composite, an attempt was made to use nanoTiO₂ and nanoclay as filler for the basalt reinforced epoxy composite (BE). The impact velocity, filler concentration and temperature are the parameters used for the study. The composites were fabricated using vacuum assisted resin infusion technique (VARI) technique. The fabricated composite specimens were tested by using erosive wear test rig as per ASTM G76 under normal incidence. The result shows that the erosion rate increases with increase in temperature and impact velocity. However, nanoTiO₂-filled BE composite exhibits lower erosion rate as compared to Nanoclay filled and unfilled composite. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM).

Abstract: Abrasion wear is a mechanical process when the surfaces of a friction coupling decay and which occurs with material removal from the softer surfaces that get into contact with the asperities of the harder surface located in the space between the coupling elements. The paper aims to determine the wear trace remained on a softer surface following the slidding of a harder one, for a brass/iron coupling. The lubrication of coupling and the processing way of the coupling surfaces are factors that directly influence the tribological behaviour of the friction coupling.

Abstract: Titanium and its alloys exhibit a unique combination of physical and corrosion resistance properties which make them ideal materials for space flight engine component such as disks and blades of compressor, marine applications, chemical industries and many bio medical applications. However the use of these materials is limited due to its poor tribological properties. Dry sliding wear tests were performed on Ti-6Al-4V using a pin-on-disc (EN31 steel) configuration. Wear rates were measured with different load and sliding velocity at a constant sliding distance. Microstructures of worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).

Abstract: Coatings from the γ-TiAl-based powder characterized by enhanced microhardness compared to that of titanium substrates were produced by the laser cladding technology. In the current paper wear mechanisms of substrates and coating materials under sliding friction conditions are described in detail. The wear of the substrate material was due to the seizure mechanism related to the mass transport of a considerable volume of the specimen material and a steel indenter. Only shallow notches without any mutual mass transport signs were observed on the coating surface after a sliding friction test.

Abstract: To improve gas turbine performance, it is essential to decrease back flow gases in the high-temperature combustion region of turbo machine by reducing the shroud/rotor gap. An abradable seal coating will function effectively. Therefore, it is significant to identify and characterize the main wear mechanisms occurring on turbo machinery seals. A high temperature and speed test rig has been developed by BGRIMM for testing the AlSi–hBN abradable seal coating and Ti-6Al-4V dummy blade. Impact velocities between 150 and 300m·s^-1 and incursion rates between 5.0 and 480 μm·s^-1 have been applied. It was found that incursion rate has a greater impact on the wear mechanism of the AlSi–hBN coating, with tests at low incursion rate showing a obvious grooving and little micro-rupture, whereas tests at high incursion rate showing significant cutting and adhesion. The present work also shown that tests at low incursion rate related to a higher IDR, which means that blade suffered a serious wear. The investigation together with SEM and XRD analysis on the coating revealed both wear and adhesion occurred at the end of the test.

Abstract: In this study, wear behaviour of AZ31 magnesium alloy shocked by Hopkinson pressure bar was measured, the microstructure morphology was observed and the effect of high strain rate impact on wear resistance and wear mechanism of the alloy were analysed. The results show that: the wear property of AZ31 is improved by the impacted in a reasonable strain rate, but when the strain rate is high enough, it will cause the alloy inactivation. The wear mechanism of the alloy is main grain-abrasion wear, accompanied with the other form of wear, and there will be adhesive wear with the increase of the strain rate.

Abstract: In this work, cutting experiments were carried out on titanium alloy Ti6Al4V by using single crystal diamond tools to investigate the effects of cutting parameters on machined surface roughness. Experimental results show machined surface roughness decreases with increases in the cutting speed within a limited range, begins to increase as the factors reaches to certain values respectively, and decreases with increases in feed rate. Cutting depth has no significant influence on the machined surface roughness. The results also show that dominant mechanisms of the single crystal diamond tools are abrasive wear and adhesion wear.