Ion-plated Al-O-N and Cr-O-N films on Ni-base superalloys as diffusion barriers

Al-O-N and Cr-O-N films were deposited as diffusion barriers between NiCoCrAlY overlay coating and Ni-base superalloy DSM11 using arc ion plating (AIP) techniques. The efficiency of the diffusion barriers was investigated at 1050 and 900 °C. The results showed that the Al-O-N barrier could inhibit the interdiffusion of the alloying elements. Unfortunately, because of deterioration of the mechanical and oxidation properties of the whole system, it could not act as a successful barrier. The Cr-O-N film could act as an active diffusion barrier by changing into an Al-rich oxide layer in high temperature annealing. The achieved interface structure can offer both the barrier properties of a dense ceramic layer and strong bond strength of a reaction-bonding zone. In addition, Cr-O-N films could improve the oxidation properties of the NiCoCrAlY coatings by 18-37%, which were influenced by the original chemical compositions of the Cr-O-N films.