| Abstract |
| In this study, during the manufacturing process for SCR420H steel we attempted to measure the atmosphere during gas nitriding and examine the formation of a compound layer accordingly. For the nitriding process, the processing time was changed at KN (Nitriding potential) 1.2 atm-1/2 at temperatures of 510 and 540 ℃ for SCR420H steel, and the formation behavior of the compound layer was observed. At the beginning of the nitriding process, the ε phase was formed due to high KN, and then the γ′ phase formed inside due to the concentration gradient. As the processing time increased, the ε phase and the γ′ phase grew, and the fraction of γ′ phase gradually increased. Meanwhile, at a nitriding process temperature of 540 ℃, the compound thickness grew and then decreased as the nitriding process time increased, and a rapid change in surface hardness was observed. The effective hardening depth was proportional to the square root of time. The formation mechanism of these nitrided compounds could be comparatively and thermodynamically analyzed using the CALPHAD (CALculation of PHAse Diagram) technique. In addition, we were able to confirm the formation mechanism of the ε phase and γ′ phase during the nitriding process through a modified Lehrer diagram.
(Received 31 March, 2025; Accepted 29 April, 2025) |
|
|
| Key Words |
| Nitriding, Microstructure, Compound layers, SCR420H, Hardness test |
|
|
 |
|
