Low temperature formation of aluminide coatings on the electrodeposited nanocrystalline Ni and its oxidation resistance with La2O3/CeO2 nanoparticle dispersion

Abstract

A systematic study was made to determine the effects of aluminizing temperature and time on the growth of the Ni2Al3 coating on the electrodeposited nanocrystalline (NC) Ni with and without La2O3/CeO2 nanoparticles by the pack aluminizing process at 550 °C/600 °C. The results show that the growth of Ni2Al3 coating obeyed the parabolic law after a delay time (t0), which decreased with increment of aluminizing temperature. The addition of La2O3/CeO2 nanoparticles significantly refined the grain of aluminide. The La2O3/CeO2-dispersed Ni2Al3 coatings exhibit a lower oxidation rate than the La2O3/CeO2-free one in air at 900 °C, because of various effects of La2O3/CeO2 on the oxidation including the grain refinement effect of the aluminide, the “reactive element effect” (REE) and the epitaxial template effect of La2O3 to promote the growth of α-Al2O3. Furthermore, the accumulation of La2O3 particles at the degradation front slightly inhibited the interdiffusion between the aluminide and Ni; while the formation of a CeO2-rich layer between aluminide and Ni–CeO2 film significantly mitigated the degradation of aluminide coatings.