Correlation between microstructure properties and the effect of WC addition on the interface, hardness and corrosion performance of thermally sprayed NiCrBSi-WC coating

Abstract

ABSTRACT Ni super-alloy is based on a powder coating of NiCrBSi – WC from flexicord wire feedstock material. The role of the CMoAlNi thick layer on the microstructure and interface properties of the coating was examined. The microstructure and interface properties were analyzed for both NiCrBSi-WC and NiCrBSi-WC/CMoAlNi thick layer using optical microscopy (OM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD). The mechanical property was evaluated by a Vickers hardness and nano-indentation measurement under 3N and 100mN, respectively. The performance of corrosion interface coatings was investigated in 3.5% of bentonite solution. The applied layer has a flame-spray morphology with unmelted and deformed particles associated with voids and porosities. In contrast, after CMoAlNi under-layers, the interface is a more compact boundary structure with no porosity or cracks. The as-sprayed NiCrBSi-WC coating exhibits high hardness (HIT≈6 GPa), and high Young's modulus (EIT≈ 240 GPa) The ability to resist cracking is significantly higher for the NiCrBSi-WC coating concerning the NiCrBSi-WC/CMoAlNi coating, 7.21 compared to 2.88 (GPA−3) x106. The electrochemical potentiodynamic polarisation results show that the NiCrBSi-WC coating's corrosion resistance is higher than that of the NiCrBSi-WC / CMoAlNi coating.