Improving adhesive strength of WC-CoCr coating with novel bimodal roughening substrate: Finite element modeling

The durability of a coating-substrate system is mainly determined by its adhesion strength. However, a major challenge is to effectively evaluate the adhesive effect after design, as measuring the adhesion strength of complex composite coatings is difficult. In this work, a bi-roughened surface of substrate was designed and its effects on the adhesive strength of WC-CoCr coatings were explored by simulation. Initially, a finite element model was established to simulate the substrate-coating system with bi-roughening (sub-roughness and sub-roughening angles) interface. In the case of monomodal Ra 7.5 μm, the adhesive strength was predicted to be only 68 MPa. While, the designed sub-roughening of Ra 0.8 μm enhanced the value to nearly 80 MPa. Moreover, the adhesive strength is further improved to above 100 MPa by tailoring the sub-roughening angle to 60°. The residual stresses along interfacial region decrease significantly for bi-roughening design, which can be responsible for enhanced adhesive strength. Additionally, individual crack growth occurs in almost every bi-roughening, and does not connect with the main crack, which result in a proportional increase in apparent interfacial shear strength. Briefly, adhesion strength is considerably improved for the bi-roughening design, which is beneficial for durability of the coatings during service.