Mechanism of Thermal Fatigue Failure on the Martensite Stainless Steel Hard-Facing Weldments

Abstract

The mechanisms of thermal fatigue failure of SUS 410 martensite stainless steel hardfacing weldments were investigated in this study. Two different types of inartensite stainless steel strip were deposited by submerged arc welding process. Specimens in this study were annealed after welding. Hardness and thermal fatigue testing was conducted. Their microstructures of deposited metal were evaluated by OM, SEM and TEM. Experimental results indicate that the hardness of weld pools decreased as PWHT temperature increased. However, the amount of precipitated carbides increased as PWHT temperature increased, resulting in increased thermal fatigue resistance. After thermal fatigue test, the M(23)C(6) carbide was found to precipitate and cracks were occured. The primary mechanisms of thermal fatigue failure were found in this study was that the separation of M(23)C(6) out of grain boundaries. The. stress of thermal fatigue produces micro-voids and fissures by precipitates, and carbide grows in the inside and causes the integrated stress of bracing and stretching. The weldment cracks as a result.