Additive layer manufacture of Inconel 625 metal matrix composites, reinforcement material evaluation

While some high performing nickel based superalloys are difficult to process through additive layer manufacturing routes, it is considered that more dilute nickel superalloy (in this case Inconel 625) based metal matrix composite may improve high temperature properties, while retaining good weldability for use in laser melting deposition technologies. In this paper, the effect of 5 wt% additions of 3 differing ceramic reinforcement particles to an Inconel 625 matrix was observed when processed by high powered laser melting, and compared to the processing characteristics of the pure matrix alloy. It was found that while additions of silicon carbide increased material hardness by 130%, levels of porosity and cracking also increased. The addition of aluminium oxide had no appreciable effect upon material hardness, while also compromising the integrity of the material. However additions of titanium carbide resulted in samples of similar density and consistency as the matrix alloy but with 30% increased hardness. However comparison of the width of single laser melted tracks of both Inconel 625 and Inconel 625 with titanium carbide composite indicated a need to further characterise the process window for this proposed MMC system.