Study on scaling of mechanically alloyed and hot pressed NbCr2 Laves phase at 1200 °C in air

Scaling behavior of NbCr2 Laves phase alloys was investigated at 1200 °C in air. The specimens were prepared by hot pressing at 1250 °C for 30 min from mechanically alloyed (MA, 20 h) powders. The scale morphology was observed by SEM and scale compositions were studied by EDS and scale phases were determined by XRD. It was found that the oxide scale had a structure of two layers: the outer layer was a porous, loosely adherent Cr2O3 layer with 8–10 μm; the inner layer consisted of CrNbO4 with 50 μm. And there were one or more breakdowns and wrinkling whereas no spallation in the scale during air cooling to room temperature. TEM analysis indicated that the grain size of the as-HPed NbCr2 Laves phase was 90–200 nm, which enhanced the metal ion diffusion outward and oxygen ion diffusion inward. The results of the present study form a theoretical and technical basis for the further research.