Effect of annealing conditions on in situ formation of Cr₂O₃ diffusion barrier

The previous investigation suggested the approach for an in situ formation of Cr₂O₃ diffusion barrier by annealing the cold-sprayed Ni coatings on 310SS. In this paper, the influences of annealing conditions on the growth kinetics of Cr₂O₃ and substrate microstructure were investigated. Results show that Cr₂O₃ formed at the selected annealing temperatures of 850, 900 and 950°C for different durations of 4, 8 and 20 h. Increasing temperature enhanced the growth kinetics of Cr₂O₃ and the Mn content in the oxide layer. The annealing process for the growth of Cr₂O₃ improves the coating adhesion compared to the as-deposited coating. However, annealing at 950°C resulted in the precipitation of chromium carbides and enhanced the element inter-diffusion across the substrate/coating interface.