High-temperature Properties of Hot-Work Tool Steel (AISI H13) Deposited via Direct Energy Deposition

Abstract

Conventionally, a defected tool steel is repaired by welding; however, that repairing does not guarantee homogeneous quality. Hence, this study focused on developing an alternative repairing technique using direct energy deposition (DED) to minimize thermal effects. To investigate a repair using powder-fed DED, AISI H13 powder was deposited onto heat-treated JIS SKD61. The deposited material was observed through scanning electron microscopy and its hardness and tensile properties were determined at 25, 200, 400, 600, and 800 °C. The deposited material showed different hardness distributions in its cross-section, revealing four representative features. The deposited region and dilution showed a hardness of 620 HV with a dendrite structure. The hardness decreased to 490 HV in the heat-affected zone, revealing a tempered martensite structure; however, it increased to 550 HV in the substrate and revealed a typical martensite structure. At all temperatures, the deposited material showed higher hardness than heat-treated SKD61. Moreover, it showed higher ultimate tensile strength and lower elongation in the deposited region. Therefore, this result indicates that without pre- or post-heat treatment, a part repaired using powder-fed DED can have better mechanical properties than heat-treated SKD61.