Designing TiB₂/Cr multilayer coatings on Ti6Al4V substrate for optimized wear resistance

The difference in mechanical properties between the TiB₂ coating and the Ti6Al4V substrate can deteriorate the wear resistance of the TiB₂ coating. To enhance the TiB₂-based coating’s ability to deform in coordination with the ductile Ti6Al4V substrate and improve its tribological performance, the TiB₂/Cr multilayer coatings were designed and deposited on Ti6Al4V substrates by magnetron sputtering. Results reveal that the FEM stress distribution of the TiB₂/Cr multilayer coatings was optimized by varying the ceramic–metal thickness ratio (Q). As Q decreased from 1.0 to 0.5, the fracture toughness and adhesion strength of the coatings improved. The multilayer coating with Q = 0.5 exhibited the best toughness, crack propagation resistance (CPRs), and the smallest equivalent stress area, leading to a threefold enhancement in wear resistance compared to the TiB₂ monolayer coating. However, further reduction of Q to 0.3 diminished wear resistance due to low hardness and significant stress concentration. Thus, there is an optimal balance between hardness, toughness, and stress distribution for achieving improved wear resistance in the multilayer design. Moreover, a notable correlation was observed between CPRs and the wear resistance of TiB₂/Cr multilayer coatings.