Structure of Plasma-sprayed NiAl-Al₂O₃ Gradient Ceramic Coatings

NiAl/Al2O3 gradient ceramic coatings were fabricated by plasma spraying.The microstructure and phase structure of gradient coatings were analyzed,the hardness and porosity were tested.The gradient coatings showed the characteristic that structure was nonuniform macroscopically but consecutive microscopically.The gradient coating was multi-phase composite including α-Al2O3,γ-Al2O3,δ-Al2O3,Ni,NiO,TiO2 and Ni-Al intermetallic compound.The porosity of NiAl layer was the least and Al2O3 layer was the most,and the hardness of coating increased as the Al2O3 increased.