| With the powder of5～15μm (A) and10～30μm(B) as feed materials, high velocity oxygen-fuel (HVOF) and low temperature high velocity oxygen-fuel (LT-HVOF) techniques have been employed to collect WC-10Co4Cr splats and prepare its coating. The phase constituent, residual stress, wear resistance, gas and slurry erosion performance of coating have been observed and measured by means of X-ray diffractometer, friction wear testing machine, gas blasting erosion tester and slurry-erosion friction wear testing machine, separately. Results show that:(1) LT-HVOF technique has been adopted to collect WC-10Co4Cr splats and produce its coating using A powder as research object. It’s been concluded that as the spraying distance is220-280mm in LT-HVOF.In LT-HVOF process the collected powder was slightly melted, while in HVOF powder was half melted, and there are initial finer A powder more likely to melt in both processes. Compared with B coating, A coating has a lower surface roughness, the main crystalline phase of HVOF-A coating is W2C, which decrease the bond strength and micro-hardness, the crystalline phase of other coatings is mainly WC.(2) HVOF-A Coating possesses typical lamellar structure, while in the rest of three coatings evident lamellar structure has not been observed. Meanwhile, the crack expands along Cr-rich strip existing in HVOF-A Coating, the crack of other three coatings spreads along Co/Cr binder phase bypassing hard phase WC. Cr-rich strip can significantly decrease the toughness and wear resistance of coating.(3) HVOF-A coating has maximum volume loss in gas blasting erosion process, while that of LT-HVOF-B coating is the least. Gas blasting erosion performance of WC coating is related to erosion angel and lamellar structure. In30°erosion angel, gas blasting erosion performance is characterized by fatigue flake and slightly cutting, complete fatigue flake in90°. The typical lamellar structure can produce large area of high-density concave and induce fatigue crack, decrease extension resistance and improve erosion volume loss.(4) Slurry erosion performance of coating is insensitive to erosion angel, and coarse powder can help improve this performance. Slurry erosion is fatigue flake in HVOF process and slightly cutting in LT-HVOF process. HVOF-B coating is in possession of high toughness and prone to non-uniform multiple plastic deformation, which produces high-density flake concave. WC hard phase splats with big size can provide more "shadow effect" and protect Co/Cr binder phase from cutting, thus LT-HVOF-B coating has better slurry erosion resistance performance. |
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