Enhanced biocompatibility of a Ni–Cr alloy prepared by selective laser melting: a preliminary in vitro study

Abstract

Against a general consensus regarding the high toxicity and low biocompatibility of cast nickel–chromium (Ni–Cr) alloys, the in vitro biocompatibility of selective laser melting (SLM)-fabricated Ni–Cr alloys was investigated and compared with that of cast alloy. Using a single Ni–Cr alloy powder, two SLM alloys with high (SLM_a) and low (SML_b) porosity were prepared by adjusting the laser process parameters in addition to a cast alloy. The alloys were studied in terms of their microstructure, metal ion release, and cell response. All three alloys were composed of only the γ (face-centered cubic) phase. However, both SLM alloys showed more homogeneous dispersion of Ni, Cr, and molybdenum elements and finer grain formation than the cast alloy. Immersion test results indicated that both SLM alloys (in particular, SML_b) exhibited a significantly lower Ni ion release than the cast alloy (P < 0.001). A water-soluble tetrazolium salt-8 assay also showed that the viability of L929 mouse fibroblasts was significantly higher for both SLM groups (in particular, SML_b) than for the cast alloy group (P < 0.001). Thus, the combined results of this in vitro study suggest that the SLM-processed Ni–Cr alloys exhibited greatly enhanced biocompatibility in comparison with the cast alloy. Keywords: Metallurgy, Ni–Cr alloy, Selective laser melting, Microstructure, Biocompatibility