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采用在Ni基上复合电镀Ni-Al2O3和Ni-Y2O3复合涂层后在800°C下扩散渗铬的方法,分别制备了Al2O3和Y2O3改性渗铬涂层。采用相同的工艺在单Ni镀层上直接渗铬,获得一种不含氧化物粒子的渗铬涂层。分析了Al2O3和Y2O3影响渗铬涂层的氧化和腐蚀性能的机理。组织结构分析表明,Al2O3和Y2O3能明显抑制在渗铬过程中涂层晶粒的长大。800°C循环和75%Na2SO4+25%NaCl混合盐腐蚀试验结果表明:与在单Ni镀层上直接渗铬相比,Al2O3和Y2O3改性的渗铬涂层所具有的细晶结构促进了保护性氧化物形成元素Cr沿晶界向氧化前沿的快速扩散,从而有利于致密保护性Cr2O3氧化膜的快速形成,使得改性的渗铬涂层表现出更优异的抗循环氧化和混合盐热腐蚀性能。
Al 2 O 3 and Y 2 O 3 modified chromizing coatings were prepared by Ni-based composite plating Ni-Al 2 O 3 and Ni-Y 2 O 3 composite coatings after diffusion chromizing at 800 ° C. The same process is used to directly chromize a single Ni coating to obtain a chromia-free coating containing oxide particles. The mechanism that Al2O3 and Y2O3 affect the oxidation and corrosion properties of chromized coatings was analyzed. Tissue structure analysis shows that Al2O3 and Y2O3 can significantly inhibit the grain growth during chromizing. The results of the mixed salt corrosion test at 800 ° C and 75% Na2SO4 + 25% NaCl show that the fine grained structure of Al2O3 and Y2O3-modified chromized coatings promotes protection compared to direct chromization on single Ni coatings The rapid diffusion of the Cr, which is the oxide of the formation of the oxide, along the grain boundaries toward the front of the oxide facilitates the rapid formation of a dense and protective Cr2O3 oxide film so that the modified chromized coating shows more excellent resistance to cyclic oxidation and mixed salt hot corrosion performance.