Formation of intermetallic phases is steels of the Fe-Cr-Ni-Co-Mo system

The processes are considered in which the carbide and intermetallic phases are formed in the martensite ageing Fe-Cr-Ni-Co-Mo steels during heating up It is shown, that in the researched steels two or three temperature stages of the solid solution decomposition are observed. In the carbon-containing steels, the carbides or carbonitrides are recovered in sequence. Moreover, the solid solution decomposes into two isomorphous solid solutions on the basis of α-Fe and α-Cr. Also, sigma or R-phases are formed. In non-carbon steels only two latter stages are observed. At high heating temperatures the R-phase dissolves and the Fe2Mo Laves phase precipitates. Determined are the compositions, temperature ranges of the phases being formed as well as the influence of the phases on the mechanical properties