Abrasive Wear Behaviour of Heat Treated En31 Steel

Ni-Cr-Mo steels are widely used in machine part members, gears and shafts. Steels with higher carbon content (similar to 1%) are used for heavy machine parts and bearings. Abrasive wear resistance is often a very important requirement for these high carbon steels, apart from sliding wear properties. In the present study, En31 steel was subjected to varying heat treatments to generate different microstructures. An attempt has been made to correlate the two body abrasive wear resistance with the bulk hardness and microstructures. The microstructures were studied through a combination of scanning electron microscopy (SEM), energy dispersive spectrometer attached to SEM (i.e. SEM-EDS) and X-ray diffraction (XRD). The bulk hardness decreased with increase in tempering temperature from 423 K to 848 K. The precipitation of Cr7C3 after 598 K tempering did not cause an appreciable increase in the hardness. At higher tempering temperatures (848 K), the martensite decomposed to give ferrite and cementite. The abrasive wear tests were carried out on hardened and tempered specimens. The abrasive wear mass loss increased with increase in the tempering temperature. Hardness had a direct correlation with the two body abrasive wear behaviour in En31 steel - increase in hardness increased the abrasive wear resistance. The important material removal mechanism were micro cutting and micro ploughing, the relative contribution of each to total wear loss was influenced by abrasive wear test conditions.