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

Yb:YAG 디스크로 레이저 표면 용융 경화된 SKD61 열간금형강의 경도와 미세조직에 미치는 레이저 출력의 영향

  • Lee, Kwang-Hyeon (Busan Laser Application Support Center, Korea Institute of Machinery & Materials) ;
  • Choi, Seong-Won (Dept. of Material Science and Engineering, Pusan National University) ;
  • Kang, Chung-Yun (Dept. of Material Science and Engineering, Pusan National University)
  • 이광현 (한국기계연구원 부산레이저기술지원센터) ;
  • 최성원 (부산대학교 재료공학부) ;
  • 강정윤 (부산대학교 재료공학부)
  • Received : 2015.04.14
  • Accepted : 2015.06.10
  • Published : 2015.06.30

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 $M_{23}C_6$ of 500 nm and the VC and $Mo_2C$ of a nano meters on boundary of dendrite.

Acknowledgement

Supported by : 한국연구재단

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