超音速火焰喷涂微米碳化物涂层的组织与性能

Microstructure and Resistance to Corrosion by Hydrochloric Add of Carbide Coatings Prepared by High Velocity Oxy-Fuel Spraying

WC-Co,NiCr-Cr3C2喷涂层耐冲蚀、耐磨性优良,但耐盐酸腐蚀报道较少。为此,采用超音速火焰喷涂(HVOF)工艺制备了WC-Co和Cr3C2-NiCr涂层,测定了涂层的孔隙率和结合强度,用XRD分析了涂层腐蚀前后的相结构及在1mol/LHCl溶液中浸泡涂层材料的失重情况,分析了涂层的均匀腐蚀机理。结果表明:WC-Co和Cr3C2-NiCr涂层组织较为致密,孔隙率分别为2.67%,4.39%,结合强度分别为49.576,41.023MPa。Cr3Cr2-NiCr涂层中相结构复杂,涂层中Cr3C2少量分解且含有非晶相;经1mol/LHCl溶液浸泡后WC-Co涂层和Cr3C2-NiCr涂层失重较少。涂层的腐蚀机理为选择性腐蚀。缺陷越少涂层的耐蚀性越好,减少涂层中的孔隙、显微裂纹和夹杂等缺陷是提高涂层耐蚀性的关键。

WC-Co and Cr3C2-NiCr coatings were prepared on 45 steel substrate by means of high velocity oxy-fuel spraying(HVOF).The porosity and bonding strength of the sprayed coat-ing were measured.The changes in the phase structures of the coatings before and after immersion in 1 mol/L HC1 solution were analyzed by means of X-ray diffraction,while their weight losses after immersion in the acidic solution were determined by weig-hing.Results showed that WC-Co and Cr3C2-NiCr coatings were compact and had a porosity of 2.67% and 4.39%,respectively,while their binding strength were 49.58 MPa and 41.02 MPa.Moreover,Cr3 C2-NiCr coating had complex phase structure and contained a small amount of amorphous phase,accompanied by partial decomposition of Cr3 C2.After immersion corrosion in 1 mol/L HC1 solution,WC-Co and Cr3 C02-NiCr coatings showed slight weight loss.The two types of coatings immersed in hydro-chloric acid solution were dominated by selective corrosion,and the coatings with less defects had better corrosion resistance.Therefore,it would be imperative to reduce the porosity,micro-cracks,and impurities in the coatings so as to improve the corro-sion resistance.