Structure and wear behavior of NiCr–Cr3C2 coatings sprayed by supersonic plasma spraying and high velocity oxy-fuel technologies

Abstract

The 25%NiCr–Cr3C2 coatings in the experiment were sprayed on 1045 steel substrates by supersonic plasma spraying (SPS) and high velocity oxy-fuel (HVOF) technologies. The microstructures of the coatings were evaluated using environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector (EDX); the phase composition and chemical composition were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS); the distribution status and quantity of pores were assessed by an software named as ImageJ2x; the bonding strength, micro-hardness, elastic modulus were respectively experimented and analyzed by different equipments and methods. Besides, wear properties of coatings were determined by UMT-3MT. The results showed that both coatings fabricated by SPS and HVOF had a high micro-hardness, elastic modulus and low porosity; The phase composition of both coatings were similar to that of the NiCr–Cr3C2 feedstock, while the coating deposited by HVOF (HVOF coating) produced a new compound Cr23C6 and was somehow oxidized for the emerging of oxygen analyzed by XPS. Both coefficient of friction (COF) and the mass loss of coating deposited by SPS (SPS coating) were lower than those of HVOF coating under same test conditions. The HVOF coating had an obvious spalling and a deeper scratch. And there was a great deal of micro-cracks around the scratch, especially on both ends of scratch. The main wear mechanisms of both coatings were abrasive wear and lamellar spalling.