Effect of thermal cycling induced phosphorus grain boundary segregation on embrittlement of welding heat affected zones in 2·25Cr–1Mo steel

Abstract

Phosphorus induced embrittlement of welding heat affected zones (HAZs) in a 2·25Cr–1Mo steel was examined by measuring the ductile to brittle transition temperature (DBTT) of the HAZs simulated with a peak temperature of 1320°C at different welding heat inputs. At the same heat input, the DBTTs of the HAZs in the P doped samples were apparently higher than those in the undoped samples and phosphorus grain boundary segregation was mainly responsible for the DBTT increase. A critical welding heat input was found to be between 36 and 100 kJ cm⁻¹, being close to 60 kJ cm⁻¹, at which the maximum segregation of phosphorus could be produced during the corresponding thermal cycling, leading to the maximum DBTT difference between the P doped and undoped samples.

Keywords:

• Welding
• Grain boundaries
• Segregation
• Embrittlement

Acknowledgements

This work was supported by the National Natural Science Foundation of China (grant no. 51071060) and the Science and Technology Foundation of Shenzhen (grant no. JCYJ20120613115121482).