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Abstract:
The low fracture toughness of NiAl at room temperature is one of the critical issues limiting its application in aircraft engines. It has been previously shown that a small addition of rhenium and alumina significantly improves the fracture toughness of hot-pressed NiAl. In this work, NiAl with an admixture of rhenium and alumina was produced by laser powder bed fusion additive technology (LPBF). The purpose was to compare the fracture toughness, bending strength, and microhardness of the NiAl-Re-Al2O3 material produced by LPBF and hot pressing (HP). Our results show that the LPBF material has lower fracture toughness and bending strength compared to its hot-pressed equivalent. Microcracks generated by thermal stresses during the LPBF process were the primary cause of this behavior. To improve the LPBF material, a post-processing by HP was applied. However, the fracture toughness of the (LPBF + HP) material remained at 50% of the KIC of the HP material. This study supports hot pressing as a suitable processing method for NiAl with rhenium and alumina additions. However, a hybrid approach combining LPBF and HP proved to be highly effective on the raw NiAl powder, resulting in superior fracture toughness of the final material compared to that consolidated by singular HP.

Keywords:
NiAl intermetallic,additive manufacturing ,hot pressing ,mechanical properties