Effect of Chromium on Creep Rupture Strength and Microstructure of 10Cr-2Mo-V-Nb Heat Resisting Steel

Abstract

The effect of chromium content on high temperature properties of ferritic heat resisting steel containing Mo, V and Nb was studied. The amount of chromium content was varied from 3% to 15% in order to obtain the optimum value. The tempering hardness and tensile strength were measured and the creep rupture tests were carried out in the temperature range from 550°C to 700°C. The microstructure was observed by transmission electron microscope.
The results indicated that the low chromium steels had a good tempering resistance in shorter term tempering, but had a tendency to soften remarkably after longer term tempering. As increasing the chromium content up to 8%, the tensile strength increased but the ductility decreased. It was observed in transmission electron microscopy that the coalescence of precipitates was accelerated, but the recovery of matrix was markedly retarded with increase in chromium content.
It was concluded that the optimum chromium content obtained from creep rupture tests and so on, was 10% at the temperature of 600°C.