Effects of WC ratios on bead size and crack initiation in forming WC-Co cemented carbides by the laser metal deposition

Abstract

Enhancing the durability of molds, jigs, and tools is crucial for the industry, and one approach to achieve this is by forming a metallic layer with high hardness on their surfaces. Metallic layers with high hardness can be formed through laser metal deposition (LMD), which is one of the additive manufacturing processes, using cemented carbide powder. However, crack initiation typically occurs inside cemented carbide layers formed by the LMD. Therefore, achieving a cladding process for cemented carbide layers without cracks is desired for practical applications. In this study, the effects of tungsten carbide (WC) ratios in WC-Co cemented carbide granulated powder on formed bead size and crack initiation during the LMD processing were investigated. The number of cracks generated during the LMD processing was evaluated using an acoustic emission (AE) technique. The number of burst-type AE signals generated was counted as the number of cracks. Seven types of WC-Co cemented carbide granulated powders with WC ratios ranging from 30.5 to 92 mass% were prepared. Beads were formed using each powder through the LMD, with AE signals being measured. In the case of a WC ratio of 42.9 mass% or less, no crack was observed. On the other hand, cracks were observed when the WC ratio was 53.9 mass% or greater, and the number of cracks increased with an increase in the WC ratio.