2022 年 108 巻 9 号 p. 656-665
The hydrogen trapping of V and Mo carbide precipitates were investigated using tempered martensitic steels (0.3%C-1.2%Cr and 0.2%V or 1.0%Mo), for the purpose of improving hydrogen embrittlement strength. The effect of tempering conditions on hydrogen trapping energy and trapped hydrogen content was studied. The trapped hydrogen content of V or Mo carbide was maximum value at the tempering temperature of 600°C for 1 hour and the trapped hydrogen content in Mo carbide was more dependent on tempering temperature than V carbide. In cases where the tempering time exceeded 1 hour at a tempering temperature 600°C, the trapped hydrogen content in Mo carbide decreased remarkably. At the tempering temperature of 600°C for 1 hour, the hydrogen trapping energy in V carbide was about 57 kJ/mol, which was a little higher than in Mo carbide. The V and Mo carbide at the tempering temperature of 600°C for 1 hour were identified cubic VC and MoC by TEM observation, respectively. The both form were plate-shaped with a width of about 1nm and a length of about 20 nm or less. At a tempering temperature of 650°C for 1 hour or 600°C for 24 hours, MoC was significantly reduced and precipitated rod-shaped hexagonal Mo2C. It was presumed that this was the cause of the decrease in the hydrogen trapped content of Mo carbide under these tempering conditions.
