The purpose of this experiment is to study the friction and wear properties of new alloy steel for brake disc of high-speed train.
Taking quenched and tempered Cr-Ni-Mo alloy steel for high-speed train brake disc as the research object. Microstructure and energy dispersive spectrometer analysis were carried out by transmission electron microscope (TEM), dry friction experiments were carried out by ball-disc contact under atmospheric environment at 25°C, 200°C, 400°C and 600°C, respectively. Friction surface and friction cross section morphology were observed by scanning electron microscope (SEM), and abrasive particles were analyzed by energy dispersive spectrometer (EDS).
Microstructure of quenched and tempered Cr-Ni-Mo alloy steel is lath martensite, a large number of fine second phases are distributed in lath, which are carbides of Fe, Cr and Mn; at 25°C, both the second phases and the matrix fall off the friction surface, and fallen matrix form abrasive particles similar in size and shape to the hard second phase during friction, abrasive wear is the main mechanism; at 200°C, abrasive wear and adhesive wear are the main wear mechanisms; at 400°C, oxidative wear and adhesive wear are the main mechanisms; at 600°C, crushed oxides have large volume, oxidative wear is the main mechanism.
Morphology of friction surface is observed by SEM, because of roughness of friction surface, the difference of depth of field is too large, it is difficult to accurately judge the properties of abrasive particles by directly analyzing the friction surface with EDS. Therefore, samples are cut, ground and polished, morphology of friction cross section is observed by SEM, the properties of abrasive particles are determined by EDS analysis, thus effectively avoiding the misjudgment of abrasive particles caused by the difference of depth of field in EDS analysis. In addition, the role of second phase in the friction process is studied by combining the morphology and EDS analysis of TEM and SEM.
