Effect of QPQ on Wear and Corrosion Behavior of 316L Stainless Steel

 To address the low hardness of 316L austenitic stainless steel and its susceptibility to adhesive and abrasive wear during service, as well as the corrosion deterioration commonly induced by conventional surface strengthening treatments, the synergistic evolution of surface microstructure, wear resistance, and corrosion resistance under different key salt bath nitrocarburizing (QPQ) process parameters was systematically investigated. ASTM A479 316L stainless steel was selected as the substrate. A three-factor, three-level orthogonal experimental design was adopted to regulate cyanate concentration, nitriding temperature, and nitriding time. After salt bath nitrocarburizing–polishing–post-oxidation treatment at 400 ℃ the morphology and phase constitution of the modified layer were characterized by SEM and XRD. Mechanical and electrochemical properties were systematically evaluated through microhardness testing, pin-ondisk friction and wear tests, and potentiodynamic polarization measurements in 3.5 wt.% NaCl solution. After QPQ treatment, a composite surface structure consisting of a Fe₃O₄ oxide film, an iron-nitride-dominated compound layer, and a diffusion layer was formed, with a modified layer thickness ranging from 41.33 to 74.58 μm. The surface hardness increased significantly from approximately 280 HV0.3 for the substrate to 1112.47-1275.09 HV0.3. Orthogonal analysis revealed that the significance order affecting wear volume was nitriding time > nitriding temperature > cyanate concentration. Among all conditions, process No. 6 (36.2~38.2%、580℃、2h) exhibited the lowest wear volume of 2.09×10⁶ μm³. Electrochemical results indicated that, compared with the substrate, QPQ-treated specimens showed a negative shift in corrosion potential and an increase in corrosion current density, suggesting an overall reduction in corrosion resistance in Cl- -containing media. Nevertheless, under different processing conditions, specimen No. 6 exhibited a relatively low corrosion current density (Icorr = 3.265×10⁻⁴ A·cm⁻²) and a relatively high polarization resistance (Rp = 1.019×10² kΩ·cm²). For 316L stainless steel, a QPQ treatment condition of 580 ℃×2 h with a cyanate concentration controlled at 36.2~38.2% can simultaneously achieve high surface hardness and excellent wear resistance while maintaining relatively moderate corrosion deterioration. Excessively long nitriding time or excessively high cyanate concentration promotes thickening of the compound layer and CrN precipitation, thereby aggravating surface embrittlement and defect formation, which synergistically enhances wear failure and Cl⁻corrosion sensitivity