Effect of Cr element on the microstructure and oxidation resistance of novel NiAl-based high temperature lubricating composites

Highlights: • Ti₃AlC₂, TiC, Ti₃Al and AlCr₂ are formed in the process of sintering. • The grain size of the composite is obviously smaller with the addition of Cr. • Some smaller precipitated phases distribute along the grain boundaries. • The oxidation resistance of the composite is improved with the addition of Cr. • The oxidation surface covers with a dense and uniform NiAl₂O₄ oxide layer. This research focused on the effect of Cr element on the microstructure and oxidation resistance of NiAl-based composites. The grain size of the composite was smaller with the addition of Cr and some smaller precipitated phases distributed along the grain boundaries. The oxidation resistance of the composite was improved, which was probable due to Cr could accelerate the transformation of metastable θ-Al₂O₃ to stable α-Al₂O₃ and decreased the oxidation rate. Meanwhile, the oxidation surface covered with a dense and uniform NiAl₂O₄ oxide layer, which could effectively slow down the diffusion of elements and further improved the oxidation resistance.