다이오드 레이저를 이용한 탄소강 환봉의 표면변태 경화특성

Characteristics of Surface Transformation Hardening for Rod-shaped Carbon Steels by Diode Laser

Laser Transformation Hardening(LTH) is one branch of the laser surface modification processes. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation(A₃), which results from utilizing a beam with a larger size and lower power density comparatively. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser whose beam absorptivity is better than conventional types of lasers such as CO₂or Nd:YAG laser. Because a beam proceeds on the rotating specimen, the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.