Effect of Heat Treatment on Microstructure of Modified Cast AISI D3 Cold Work Tool Steel

The effects of heat treatment on the microstructure of modified cast high chromium high carbon AISI D3 steel were studied. The modified AISI D3 steel was developed by replacing part of chromium with niobium and titanium, in which chromium carbide was partially replaced with MC carbides. The cast samples produced by investment casting were heat treated under different conditions. The microstructures of the samples were studied by optical microscope and scanning electron microscope equipped with EDS analyzer. To determine the optimized homogenizing process, the effects of homogenizing treatment on the microstructure and the morphology of carbides were also studied. The results show that the MC carbides are not changed in shape and amounts during high temperature homogenizing, whereas the M3C carbides are reduced in amount and become semiglobular in shape, and the homogeneity of micro-structure is improved.