The precipitation and transformation of secondary carbides in a high chromium cast iron

The precipitation and transformation of secondary carbides in a newly developed 16Cr–1Mo–1Cu cast iron subjected to a destabilization heat treatment was investigated. The results showed that the initial fine secondary carbide precipitation from the austenite matrix consist of (Fe,Cr)23C6. Two kinds of (Fe,Cr)23C6 carbides initially precipitated: one is cubic with a cube–cube orientation relationship with the austenite matrix, and the other is grainy with no orientation relationship with the matrix. The latter carbide may be precipitated in the cooling process after a destabilization treatment. With prolonged holding time, the fine (Fe,Cr)23C6 carbides have transformed into M7C3 rods with an orientation of [100](Fe,Cr)23C6[100](Fe,Cr)7C3 and (01¯5)(Fe,Cr)23C6(010)(Fe,Cr)7C3 between the M23C6 and M7C3 carbides.