Effects of Heating by Arc Discharge on Structure and Chemical Composition of Coatings Formed Using High Velocity Oxygen Fuel and Flame Spraying Processes

Abstract

In this study thermal effects in tungsten carbide/cobalt (WC-Co), chromium carbide/nickel chromium (Cr2C3-NiCr) and tungsten carbide/cobalt with nickel chromium boron silicon WC-Co/NiCrBSi coatings were investigated. Coatings were heated using electric arc discharge in hydrogen-argon atmosphere. XRD analysis was accomplished before and after heating. Changes of the structure and elemental composition were observed. In the case of Cr2C3-NiCr coating, heating increased crystallization thus increasing coating’s resistive properties. In the case of the WC-Co coatings, small changes of the structure were observed only after the heating at 1090 °C temperature. Amorphisation of the Cr3C2-NiCr occurred during the coating deposition process, while following heating by arc discharge at 1000 °C temperature resulted in recrystallization of the Cr2C3 and, especially, Ni phases. Amount of the crystalline Ni phase in WC-Co/NiCrBSi coatings increased only after the arc heating at 1030 °C temperature. Flame remelting of the flame sprayed WC-Co/NiCrBSi coatings resulted in formation of the more crystalline coatings in comparison with coatings heated by arc discharge and increased crystallinity not only Ni phase, but Ni3B, CrB, WC phases as well.