Abstract
The effects of boron addition on the heating processes of martensite in 0.1C-9Cr-3W-3Co steels have been studied. The steels with and without 100 ppm boron were prepared. The specimens were austenitized at 1200°C for 1.2 ks, and quenched into iced brine, resulting in formation of α' martensite laths. They were heated up to 1000°C at a rate of 10°C/min. Temperature derivative of electric resistivity, dρ/dT, decreased gradually around 500°C, increased slightly around 750°C, decreased around 810°C and largely decreased around 870°C in both steels. Observations by transmission electron microscopy revealed that the reactions were related to the formation of M7C3, dissolution of both cementite and M7C3, the precipitation of M23C6 and the austenite formation, respectively. The boron addition promotes M23C6 formation and retards the α→γ transformation.
