Effect of two-stage supersolidus liquid phase sintering on microstructure and properties of 15Cr high chromium cast iron

To solve the problems in the one-stage supersolidus liquid phase sintering (SLPS) that the sintering temperature window is narrow and the mechanical properties of the products are very sensitive to the fluctuation of sintering temperature, the high chromium cast iron (HCCI) was prepared by the two-stage SLPS technique. The effects of process parameters in the high temperature stage (HTS) on the microstructure and mechanical properties of 15Cr high chromium cast iron prepared by the two-stage SLPS were studied, and the alloys prepared by the one-stage SLPS were compared. The results show that the alloys prepared by the two-stage SLPS are composed of M₇C₃-type carbides, martensite, and a small amount of austenite. Efficient densification and the effective control of microstructure can be achieved through the high and low temperature sintering, and the relative density of high performance alloy material is more than 98.96%. The sintering temperature window is 15 ℃ wider than that of one-stage SLPS. The microstructure of the alloys is gradually coarsened with the increase of the sintering temperature and the holding time during the high temperature stage from 1225 ℃ to 1245 ℃ for 5～10 min. However, when the holding time is controlled within 10 min during the high temperature stage, the grain size is less than 26.98 μm, and the coarsening degree is acceptable. The hardness and impact toughness of HCCI prepared by the two-stage SLPS are better than those prepared by the one-stage SLPS, and the impact toughness remains stable within the sintering window with the average value of 12.10 J·cm⁻². Under the impact energy from 1 J·cm⁻² to 3 J·cm⁻², the impact abrasive wear resistance of the samples sintered by the two-stage SLPS is better than that of the samples sintered by the one-stage SLPS. With the increase of impact energy, the improvement of impact abrasive wear resistance of the alloys increases from 9.70% to 19.83%.