Biocompatibility of Ni–Cr alloys, with the same composition, prepared by two new digital manufacturing techniques

This study evaluated the in vitro biocompatibility of nickel–chromium (Ni–Cr) alloys produced via three different manufacturing techniques (casting, selective laser melting [SLM], and soft milling [SM]) from a single alloy with the same elemental composition. The microstructure, ion release, and cell viability of the alloys were studied. The Ni-based γ phase was identified for the three alloys. A segregation of the Cr and molybdenum (Mo) was observed in the cast alloy. The SLM and SM alloys exhibited a more homogeneous elemental dispersion and a finer grain formation than the cast one. Extensive porosity as well as (Mo,Cr)C carbide were generated in the SM alloy. The SLM alloy showed the lowest release of Ni ion, followed by the SM alloy (p < 0.001) and then the cast alloy (p < 0.05). The SLM alloy also exhibited the greatest density and viability of L929 mouse fibroblasts, followed by the SM alloy (p < 0.05) and lastly the cast alloy (p < 0.001). It was concluded that the SLM alloy had superior biocompatibility, cell viability of the SM alloy being slightly less but still greater than that of cast alloy.