Fabrication of a nitrided coating on a novel Ni–Cr nanocomposite with increased surface hardness

A novel type of Ni–Cr nanocomposite that had a nanocrystalline Ni matrix dispersing Cr nanoparticles was developed by electrodeposition. During plasma nitriding at 560 °C for 10 h, the nanocomposite formed a surface hard coating in which the Cr nanoparticles were internally converted into CrN. The coating decreased in thickness but increased in hardness with the increase in the Cr content from 10.8 to 30 (by wt.%). Moreover, the Cr content increase caused a shift of the hardest area of the nitrided coating from the innermost to the topmost surface, as a result of the change in the nitridation mechanism of the composite from the internal to external.