Microstructures and mechanical properties of AlCrN/TiSiN nanomultilayer coatings consisting of fcc single-phase solid solution

Abstract

AlCrN/TiSiN nanomultilayer coatings, basically consisting of single-phase fcc-AlCrTiSiN solid solution, were prepared by co-deposition method with Al30Cr70 and Ti72Si18 targets. With substrate negative bias voltage increase from 50 V to 110 V, the hardness of nanomulitlayer coatings is increased from 32.1 GPa to 36.5 GPa, and the growth behavior changes from (2 0 0)fcc preferred orientation to coexistence of both (2 0 0)fcc and (1 1 1)fcc preferred orientation. Low interfacial energy supports the epitaxial growth, resulting in an increase in strain energy of coating systems due to the lattice misfit between neighboring sublayers. Increased strain energy is overcompensated by the formation of interfacial dislocations and dislocation loops as well as fcc-AlCrTiSiN nano-twins and hcp-AlN clusters at twin boundaries. Additionally, the Cr-ion etching induces to form a thin amorphous loose layer (LL) between coating and steel substrate during the pretreatment process. High substrate bias voltage promotes the transformation of amorphous phase to the (Cr,Fe)N solid solution during the coating deposition process, resulting in a notable increase in adhesion strength.