Preparation And Research Of The High Temperature Corrosion Resistance Of The Al-Si Coating On Ni-based Superalloy

Nickel-base superalloy K438in the field of turbine engine blades and other fields to be very widely used.because it has good high temperature oxidation and thermal resistance, and has a high temperature creep strength and fracture strength. Aero-engine blades often failure due to high temperature corrosion.Nickel-base superalloy K438can not meet its performance requirements in corrosive larger occasions.The solution is make a protective coating on the surface of the substrate, the substrate borne the mechanical properties and the coating improve resistance to high temperature corrosion and protect the base metal from high temperature corrosion attack. Most protective coating is aluminized coating.Although the aluminized coating has excellent oxidation resistance, but its corrosion resistance is poor, in some corrosive environment, the coating degraded faster.The Al-Si coating can obviously improve the corrosion resistance of coating.The thesis is focusing on the high temperature oxidation and corrosion behaviors of the aluminized coating and the Si-modified aluminized coating. The microstructure evolution and degradation mechanism of the coatings were also discussed.In this paper,A Si-modified aluminized coating has been prepared by combining slurry infiltration Si and pack cementation aluminizing. As a contrast,a simple aluminized coating was developed by pack cementation aluminizing.The analyzing approaches involve mass gain measuring, microstructure observing, phase identification and chemical composition detecting. These approaches were performed with the aid of high-precision optical balance, scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrum (EDS), and X-ray diffractometer(XRD).The results demonstrate that the aluminized coating and the Al-Si coating are dense and adhere tightly to the substrate.The hot corrosion behaviors as well as the corrosion mechanism in Na2SO4and Na2SO4/NaCl (75:25,w/w) mixed salts in the static air at900℃of the K438substrate, the aluminized coating and the Al-Si coating have also been investigated.Al-Si coating has the most excellent heat resistance, followed by Al coating, the worst is substrate.Al-Si coating can significantly improve the heat resistance of the K438substrate,can be used in corrosive occasions.Also played a reference for the Al-Si coating preparation and properties of other high-temperature alloys.