Effect of NiAl- (Cr2O3, TiO2) composite coating on oxidation resistance of HH heat resistant steel

HH grade heat resistant steels are widely used in various industries due to their high temperature strength, excellent oxidation and corrosion resistance. The major degradation of these steels is due to oxidation at high temperatures. The use of diffusion barrier coating can increase the life of these steels. One of the preferred coatings is NiAl, an intermetallic compound with high oxidation resistance. In this research, the effect of Cr2O3 and TiO2 additives on the high temperature oxidation resistance of high velocity oxygen fuel (HVOF) sprayed NiAl coating was studied. At First, the NiAl powder mechanical alloying synthesis conditions were determined using Ni and Al powders. Then, each of the Cr2O3 and TiO2 powders were separately added to the NiAl mixture 5% by weight. The powder sprayed on the surface of HH steel by HVOF method. samples, SEM scanning electron microscope, hardness test, high temperature oxidation test, and thickness test were used to investigate and evaluate the quality of coated. The results showed that the composite coated steel had less porosity and had a thicker and harder surface than NiAl coating. Thermal shock resistance of samples with composite coating is much higher than that of the NiAl coating, and the maximum oxidation resistance at 1200 ° C belongs to the NiAl-TiO2 coating sample