Microstructure and Abrasive Wear Resistance of 18Cr-4Ni-2.5Mo Cast Steel

An influence of a decreased Cr content on the microstructure of the highly alloyed Cr-Ni cast steel, duplex type, melted under laboratory conditions, was characterized in the paper. The microstructure investigations were performed in the initial state and after the heat treatment (solution annealing) at 1060 degrees C as well as the phase transformation kinetics at continuous cooling was measured. The wear resistance of the investigated cast steel was tested and compared with the 24% Cr-5%Ni-2.5% Mo cast steel. The Cr content decrease, in ferritic-austenitic cast steels (duplex), from 24-26% Cr to 18% leads to the changes of the castings microstructure and eliminating of a brittle sigma phase. In dependence of the casting cooling rate, apart from ferrite and austenite, also fine martensite precipitates occur in the casting structure. It was shown that the investigated cast steel is characterised by a slightly lower wear resistance than the typical cast steel duplex grades.