Effect of cryogenic treatment on the tribological behaviour of H11 hot die steel dry sliding against D3 steel

The tribological behaviour, hardness and microstructural characteristics of vacuum and cryogenically treated AISI H11 steel at varied soaking temperature (-154 and -184 degrees C) for specific time period (6, 21 and 36 h) have been examined in this research work. The influence of selected parameters on the tribological behaviour have been studied at five levels of varying sliding velocities (0.628-1.885 m/s) and normal loads (60-140 N) through block-on-ring dry sliding wear test against hardened and tempered AISI D3 tool steel (counter face). The experiments are designed based on full factorial response surface methodology. The responses (wear rate, average coefficient of friction and maximum contact temperature) are analyzed based on plotted graphs. The results reveal that 21 h at -184 degrees C for H11steel is the optimal soak time to have the lowest wear rate. The sliding speed influences the wear rate more in comparison to load. Wear debris have shape of metallic plate. Carbide particles appeared to delaminate from the sample surface due to subsurface cracks and plastic deformation. The augmentation of apparent and bulk hardness number and wear resistance ascribed to the increase in number of fine globular secondary carbide and improved morphology of matrix microstructure of cryogenic-treated sample. It is also observed that cryogenic treatment reduces the retained austenite content to near zero.