Impact of austenitizing temperature on the wear behaviour of AISI H13 steel

Austenitizing temperature is of great importance to achieve the desired properties of die steel. It governs the number of carbides dissolved in the austenitic matrix, which later transforms to martensite. This paper intends to find out the impact of austenitizing temperature on the wear behaviour of AISI H13 die steel. Austenitizing of H13 steel is done at different temperatures, i.e., 1000 °C, 1020 °C, 1040 °C, 1060 °C and then tempering is done twice at 560 °C for two hours. H13 die steel when tempered after austenitizing at 1020 °C lath martensite of large size is produced. Whereas, quite smaller lath martensitic structure has been observed in H13 die steel tempered after austenitizing at 1060 °C. Wear test investigation carried out using a pin on disc tribometer for H13 steel pins austenitized at different temperatures against D2 steel disc having 61 HRC. It is observed that the wear volume of H13 die steel exhibits an inverse linear relationship with its austenitizing temperature due to an increase in hardness. It is seen that small protective layer like patches of oxidized debris formed on the worn surface of H13 steel austenitized at 1060 °C. Whereas, no such protective layer formation is found on H13 die steel austenitized at a lower temperature. Post wear test, subsurface cross-section study shows plastic deformation of grains just beneath the worn surface along the direction of wear tracks. H13 die steel austenitized at 1060 °C with larger grains shows plastic deformation of grains up to a greater depth. Whereas, H13 die steel austenitized at 1000 °C with finer grain exhibits plastic deformation up to a lesser depth. An increase in grain boundaries of nearly twice is also found below the worn subsurface up to 80 to 100 µm depth. The present study will help to select the austenitizing temperature for H13 die steel to have better wear resistance.