Study On Factors Of Pin-on-disc Wear Testing

Pin-on-disc method is widely used for studying adhesive wear. When evaluating the wear resistance of material in engineering or investigation, the investigative material and parameters simulating working condition instead of friction pairs materials were focused on. In this paper, the pin made of high hardness quenching steel glided on different hardness discs which were made of quenching and tempering steels. In order to clarify the effects of disc hardness, experimental stress and friction speed, weighting method was used to measure the wear rate. Moreover, the friction pair surface hardness, roughness and the phase transformation layer were characterized to figure out the mechanism. Following conclusions are drawn in the research:1. Disc material, stress and speed take great influence on the wear rate of pin. The wear rate measured was not affected by any single factor by linear rule, but as a result of several factors involved simultaneously. If these factors were not fixed in the experiment, the wear resistant sequence couldn’t be constant either. And if the gap between the wear conditions of actual instance and the parameters of experimental simulation was very huge, the evaluation of wear-ability would also be questionable.2. The wear rate of pin showed two trends with the disc hardness increasing. When the hardness of disc was below400HB, the wear rate increased with the stress and the velocity enhancing. But the opposite variety happened to wear rate with disc hardness enhancing. When the disc hardness was comparatively low and stress was great, the wear rate increased obviously with friction velocity increasing. When the hardness of disc was higher than400HB, the wear rate increased with the disc hardness and stress enhancing. When the disc hardness was comparatively high and velocity was low, the wear rate increased obviously with the increasing of stress.3. Surface hardening had occurred when different discs abraded with high hardness pin. Despite the original hardness was very different, after abraded, the hardness among different discs became more and more similar. Increasing friction velocity will slightly reduce the surface hardness, that is to say the work hardening is weakened. When the hardness of the disc was below400HB, surface hardness decreased with original hardness increasing. When the hardness was higher than400HB, the surface hardness trended consistently with the original hardness. Phenomena of low hardness disc surface hardness abnormal increasing may be related to the good plasticity. The high hardness wear debris will easily embed in matrix. Disc surface hardness may cause the wear rate appear non-linear change.4. When the hardness of disc was below400HB, surface roughness was larger than before after experiment. It sharply decreased with the original disc hardness becoming higher. On the contrary, the surface roughness was smaller than before after experiment. It slowly decreased with the original disc hardness becoming higher. The trend that surface roughness decreased with original hardness of disc increasing shows the friction pair surface roughness was directly proportional to the plastic deformation ability of the matrix.5. After pin-on-disc abraded, the phase transformation layer on the surface will appear. Ultra-fine martensite existing in the phase transformation layer demonstrated that the friction surface temperature had exceeded the austenite phase lower critical solution temperature and the friction surface had been transformed into a low hardness and high plastic austenite. The depth of phase transformation layer was the main symbol of the friction surface temperature. Phase transformation layer after friction would not impact the friction and wear behavior. With the stress and friction velocity increasing, the depth of phase changing increased. The original hardness of disc slightly affected the depth of pin surface phase transformation.