The effect of boron on the protective properties of aluminide coatings

Abstract

The effect of the formation, microstructure, phase composition, and protective properties of diffusion aluminide coatings alloyed with boron on the EI69 heat-resistant steel and the EI929 nickel alloy is studied. In the course of saturation, boron easily diffuses over the interstices of the B2 crystal lattice of aluminides, thus forming interstitial solid solutions. In this case, the Al content in the coating decreases, thereby implementing the possibility of increasing the plasticity of the coating while maintaining high protective properties. By binding refractory corrosive elements (Mo, W, Nb, etc.) into corrosion-resistant borides, boron increases the overall resistance of the coating in molten Na2SO4 and NaCl salts at 700 °C by an order of magnitude and improves the resistance of the surface to erosion wear. This makes it possible to recommend Al-Si-B coatings to be used for protecting the surface of the turbine blades of supercharging turbochargers and diesel exhaust valves.