Enhancing the Thermal Conductivity of Laser Powder Bed Fusion AlSi20 by Introducing a Novel TiC–Ti Coated Diamond Powder

The formation of pores induced by the poor wettability of diamond with the AlSi20 matrix for the powder bed fusion using a laser beam (PBF-LB) process largely deteriorates the thermal conductivity. This study proposed a new metallization strategy of depositing TiC–Ti composite coating on the surface of the diamond particles by salt bath plating to address this issue. TiC layer and TiC–Ti layer were selectively deposited on the diamond surface to produce high-quality TiC coated and TiC–Ti coated diamond particles by tuning the plating temperature and time. Compared to the TiC coated diamond particles, the TiC–Ti composite coating was more effective in promoting the densification and improving the thermal conductivity which the Ti layer played a decisive role. The TiAl₃ phase formed by the reaction of Ti layer and the AlSi matrix improved the bonding force between the diamond and matrix and hindered the formation of Al₄C₃ phase. Because of the absence of interfacial pores, the TiC–Ti coated diamond sample exhibited the highest thermal conductivity.