High Temperature Mechanical Properties of HK40-type Heat-resistant Cast Austenitic Stainless Steels

This work characterized HK40-type, cast austenitic stainless steel, as the W content was varied from 0 to 3.6 wt.%. Analysis of microstructure using optical and scanning electron microscopies showed that the alloys contained relatively large amount of Cr-carbide, Nb-compound, and MnS at the austenite grain boundary. The addition of W promoted the formation of Cr-carbide and affected the high-temperature mechanical properties. According to tension tests carried out at room temperature, 400, 600, and 800 degrees C, the alloys became significantly stronger and brittle as W content increased. The low-cycle fatigue tests showed that fatigue resistance was also increased with W addition, but an excessive amount of W decreased the fatigue resistance. The HK40-type alloys with 2.0 wt.% W exhibited best high-temperature mechanical performances.