Enhancing deformation resistance and adhesion strength by constructing the semicoherent interface structure in HfO2/Ta2O5 composite coating

Ceramic coatings on tantalum alloys are prone to premature failure under extreme conditions due to their inherent brittleness and weak interfacial adhesion. Herein, this paper reports a strategy for enhancing the deformation resistance and adhesion strength of HfO 2 /Ta 2 O 5 composite coatings by constructing a semicoherent interface structure. A controllable hafnium source is introduced into the electrolyte, enabling in-situ synthesis of HfO 2 reinforcing phases during plasma electrolytic oxidation (PEO). By quantitatively regulating Hf 4+ concentration, a (111) HfO 2 // (200) Ta 2 O 5 semicoherent interface structure is achieved in PEO coating. The results indicate that the constructed (111) HfO 2 // (200) Ta 2 O 5 semicoherent interface structure has remarkable lattice distortion, which induces dislocation pinning characteristics. Compared with conventional PEO coatings, the optimized composite coating exhibits a 71% increase in deformation resistance ( H 3 /E r 2 ) and a 56.6% enhancement in adhesion strength. The semicoherent interface dislocation effectively alleviates stress concentration and suppresses crack initiation, which improves the deformation resistance and adhesion strength of the coating. This work demonstrates that interface engineering via controlled in-situ phase formation offers a viable pathway to overcome the strength-toughness trade-off in ceramic coatings, with significant potential for applications in aerospace and nuclear industries.