Effects of laser power on hardness and microstructure of the surface melting hardened SKD61 hot die steel using Yb:YAG disk laser

Lee, Kwang-Hyeon; Choi, Seong-Won; Kang, Chung-Yun

doi:2015.33.3.54

J Weld Join > Volume 33(3); 2015 > Article

Research Paper

Journal of Welding and Joining 2015;33(3):54-61.
DOI: https://doi.org/10.5781/JWJ.2015.33.3.54 Published online June 30, 2015.

Effects of laser power on hardness and microstructure of the surface melting hardened SKD61 hot die steel using Yb:YAG disk laser

Kwang-Hyeon Lee^*, Seong-Won Choi^**, Chung-Yun Kang^**

Correspondence: Chung-Yun Kang,
Email: kangcy@pusan.ac.kr

Abstract

In this study, effect of laser power on hardness and microstructure of SKD61 Hot Die steel of which surface was melted and hardened with Yb:YAG disk laser was investigated. Beam speed was fixed at 70 mm/sec and distance between them was 0.8 mm about Laser surface melting. The only thing that was changed laser power. Laser powers were 2.0, 2.4 and 2.8 kW. No defect was found under all conditions. As the laser power increased, the penetration depth were deepened and the bead width was also widened. There was no hardness deviation of fusion zone at same laser power and it was higher than that of heat affected zone. In addition, the more laser power increased, the more hardness in fusion zone decreased. Fusion zone was macroscopically dendrite structure. However, core matric in dendrite was lath martensite of 100 nm size. There were M₂₃C₆ of 500 nm and the VC and Mo₂C of a nano meters on boundary of dendrite.

Key Words: Laser hardening, Yb:YAG disk laser, SKD61, Laser surface melting, High power disk laser