Microstructure and surface properties of Co-based brazed alloys coatings

Abstract The paper investigates the characteristics of two different manufactured high temperature brazed coatings using a cobalt based powder applied onto the surface of a stainless-steel substrate (AISI 904L). The coatings are intended to shield components exposed to high temperatures in an atmosphere where wear is expected. Energy dispersive analysis (EDX) together with scanning electron microscopy (SEM) was used to characterise the coating microstructure and morphology, and X-ray diffraction was used to identify the phase composition. Properties evaluations were carried out on the coatings’ surface characteristics, including hardness, erosion behaviour and hot corrosion resistance. The hot corrosion test was conducted at 650°C in a salt mixture that contained 75 wt. % sodium sulphate (Na2SO4) and 25 wt.% sodium chloride (NaCl). Alumina particles were used in the erosion tests, which hit the samples surface with an impact angle of 90°.The degree of corrosion attack, erosion behavior and hardness depended on the microstructure of the manufactured vacuum brazed coatings.