Anti-Corrosion Performance of the NiCrAlY Coatings Deposited by Two Different Spraying Technologies

摘要

NiCrAlY coatings are usually used as protective coatings in hot corrosive or oxidizing environment at high temperature. However, the traditional thermal spraying coatings generally have poor corrosion-resistant performance, because the coatings have many pores inner the coating and poor bonding strength between the coating and the substrate for its mechanical bonding mechanism To obtain the more excellent anti-corrosion performance coatings, the NiCrAlY coatings were deposited on 38CrMoAl substrate by a new spraying technology of laser hybrid plasma spraying (LHPS) technology. And the NiCrAlY coating was fabricated by the air plasma spraying (APS) technology simultaneously in this paper. Microstructure and anti-corrosion performance of NiCrAlY coatings were studied using an optical microscope, X-ray diffraction(XRD), a scanning electron microscope(SEM), and the Neutral Salt Spray(NSS) test. Test results indicate that the traditional APS coating's porosity is 4.0% and its bonding strength is 33MPa. Compared with the APS coatings, the LHPS coatings exhibit less pores and more dense microstructures, which average porosity is 0.9% and average bonding strength is 117MPa. Otherwise, the LHPS NiCrAlY coating has more excellent anti-corrosion performance than the APS NiCrAlY coating. The first corrosion point became visible on the surface APS coating after NSS test of 2.5 hours but 16 hours forthe LHPS coating. There are more than 60 corrosion points on the surface APS coating but only one corrosion point on the surface LHPS coating when the test time is 24 hours. When the NSS test time extended to 120 hours, the corrosion points increased to be 6 on the surface coating of LHPS but 1/5 area of the whole surface coating of APS is corroded respectively. The main corrosion mechanism of the NiCrAlY coatings deposited by the two different spraying technologies are all cavity corrosion.