ISSN   1004-0595

CN  62-1224/O4

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渗铬温度对304不锈钢渗氮与渗铬复合渗层组织与性能的影响

Effect of Chromizing Temperature on the Microstructure and Properties of the Nitriding and Chromizing Composite Layers on 304 Stainless Steel

  • 摘要: 采用辉光离子渗氮与固体渗铬复合处理方法对304不锈钢进行表面热处理,研究850、900、950和1 000 ℃不同渗铬温度对复合渗层微观组织结构和硬度、洛氏压痕以及耐磨耐腐蚀性能的影响. 结果表明:复合渗层的表面形成了连续致密且形状不规则的晶粒. 随着渗铬温度的升高,晶粒的尺寸逐渐增大,渗氮与渗铬复合渗层主要物相为Cr2N和Cr2C. 复合渗层厚度和表面硬度随着渗铬温度的增加逐渐提高,复合渗层厚度在6.15~28.41 µm之间,表面硬度在1 437.1 HV~1 749.0 HV之间. 与304不锈钢相比,复合处理明显降低了表面的摩擦系数和磨损率,900 ℃时渗层的磨损率为6.69×10−7 mm3/(N·m),耐磨性能提高了约20倍. 复合渗层在经历了3 865 h的中性盐雾腐蚀后仍未发生明显腐蚀,表明复合渗层具有优良的耐中性盐雾腐蚀性能. 研究表明,适当提高渗铬温度可增强原子扩散动力,从而提高了复合渗层的厚度,显著提高了复合渗层的耐磨性能和耐腐蚀性能;过高的渗铬温度使渗层内应力增加,复合渗层内产生微裂纹,导致渗层力学性能下降.

     

    Abstract: 304 stainless steel was treated by a combined surface modification process of glow discharge nitriding and solid powder pack chromizing. The effects of different chromizing temperatures (850, 900, 950, and 1 000 °C) on the microstructure, surface hardness, Rockwell indentation behavior, wear resistance, and corrosion resistance of the composite chromized layers were systematically investigated. The results showed that the surface of the composite layers consisted of continuous, dense grains with irregular morphology. As the chromizing temperature increased, the grain size gradually enlarged. The main phases identified in the composite layer were Cr2N and Cr2C. Both the thickness and surface hardness of the layer increased with the chromizing temperature, ranging from 6.15 to 28.41 μm and from 1 437.1 HV to 1 749.0 HV, respectively. Compared with untreated 304 stainless steel, the composite layer significantly reduced the friction coefficient and wear rate, with the lowest wear rate of 6.69 × 10-7 mm3/(N·m) at 900 °C, representing a ~20-fold improvement in wear resistance. After 3 685 h of neutral salt spray testing, no obvious corrosion was observed on the composite layer, indicating excellent corrosion resistance. The study indicated that appropriately increasing the chromizing temperature could enhance the driving force for atomic diffusion, thus increasing the thickness of composite layer, and significantly improving its wear resistance and corrosion resistance. However, too high chromizing temperatures induced higher internal stresses within the layer, resulting in microcracks in the composite layer and subsequent degradation of its mechanical properties.

     

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