Corrosion and isothermal interdiffusion properties of Ni–Al coatings under simulated biomass combustion conditions

Abstract

The main issue with using biomass fuels in power plants is fireside corrosion. Applying corrosion-resistant coatings is one potential choice. The current study examines how a Ni–Al diffusion coating on austenitic stainless steel reacts to corrosion and interdiffusion (TP347H). Nickel was electrolytically deposited to create Ni–Al coatings, which were then pack aluminized at 650 °C. With an internal layer of Ni and a Ni2Al3 outer layer, a homogenous and dense Ni–Al coating was created. Samples were heated to 560 °C for 168 h in an environment designed to simulate the combustion of biomass. A localized corrosion attack was the result. By using isothermal heat treatment in static air at 650 °C or 700 °C for up to 3000 h, interdiffusion was examined. In the course of the interdiffusion process, the Ni2Al3 eventually changed into NiAl and Ni3Al. At both temperatures, porosity formed at the intersection of the Ni–Al coating and the Ni layer and grew with time.