Evolution of Carbide Precipitates in 1.25Cr-0.5Mo Steel During Simulated Postweld Heat Treatment

In the present work, the effect of simulated postweld heat treatment (SPWHT) on the microstructure of 1.25Cr-0.5Mo steel was systematically studied. Microstructure is mainly composed of ferrites and carbides after quenching-tempering and SPWHT. Outstanding features of carbides, including distribution, composition, morphology, and size, are identified by means of an electron-probe microanalyzer and a transmission electron microscope. The results show that the carbides coarsen and gather along grain boundaries and M7C3 transforms into M23C6 in situ.