Thermal resistance of Al2O3 coating produced by electrostatic spray deposition method

Results of experimental investigation of effect of Al2O3 nanoparticle sizes on morphology and thermal resistance of Al2O3-based coating deposited by means of electrostatic spray deposition technique on X10CrAlSi18 steel substrate are presented in this paper. Microscopic observations showed that all coatings were porous and built from agglomerates, whose size was depended on the size of primary Al2O3 nanoparticles. It was noticed that surface roughness was lower for primary Al2O3 nanoparticles of larger size. Thermal cycles caused many cracks in the coating, which were located around the agglomerates. Larger number of cracks was formed in the coating produced from smaller Al2O3 particles, and it was observed that the number of cracks decreased with an increase of Al2O3 particle size, but at the same time, the depth of these cracks increased. With an increase of the number of thermal cycles, the surface roughness and the number of cracks slightly decreased. No delamination of the coating was noted at any specimen after all thermal cycles.