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

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.