32Cr2Mo2NiVNb钢盐浴氮化工艺

Salt-bath Nitriding Process for 32Cr2Mo2NiVNb Steel

目的将盐浴氮化工艺用于32Cr2Mo2NiVNb钢的表面处理。方法采用盐浴氮化工艺处理32Cr2Mo2NiVNb钢,通过对金相组织、力学性能、断口形貌、耐蚀性能、高温耐磨性能等的测试分析,研究该工艺对32Cr2Mo2NiVNb钢组织和性能的影响,验证该工艺对32Cr2Mo2NiVNb钢的适用性。结果32Cr2Mo2NiVNb钢盐浴氮化后,基体组织为均匀的细针状索氏体+少量游离铁素体,渗氮层深度约为0.23 mm,化合物层深度均匀,约为17μm,渗氮层疏松度、氮化物、脆性评级均达到1级;表面硬度为1011HV0.3,较氮化前提高153.4%;抗拉强度、拉伸断口形貌均无明显变化,断后伸长率、断面收缩率、冲击吸收能量仅小幅降低;耐中性盐雾时间为镀硬铬试样的6.3倍;经190 s高温磨损的表面磨痕细小均匀,磨损失重较镀硬铬试样降低62.8%。结论盐浴氮化工艺不损害32Cr2Mo2NiVNb钢组织、强度等,仅使塑性、韧性指标小幅降低,相较于镀硬铬工艺,可显著提高32Cr2Mo2NiVNb钢的耐蚀性、高温耐磨性,对32Cr2Mo2NiVNb钢的工艺适用性良好。

Objective To develop a new salt-bath nitriding process for 32Cr2Mo2 NiVNb steel surface treatment. Methods The32Cr2Mo2 NiVNb steel was treated with the new salt-bath nitriding process. The influences of the new salt-bath nitriding process on the microstructure and mechanical properties of 32Cr2Mo2 NiVNb steel were concluded based on the analysis of several tests such as salt spray test and hardness test. The applicability of the salt-bath nitriding process for 32Cr2Mo2 NiVNb steel was verified in this paper. Results After the salt-bath nitriding process,the 32Cr2Mo2 NiVNb base material was composed of uniform fine needle-like sorbite ＋ small amount of free ferrite,the depth of the nitriding layer was about 0. 23 mm,and the compound layer showed an even thickness of about 17 μm. The level of the brittleness,nervation and wave-like nitrid,porosity of nitrided case all reached grade I. The hardness of 32Cr2Mo2 NiVNb steel surface after salt-bath nitriding treatment was 1011HV0. 3,which was 250% of the surface hardness without salt-bath nitriding treatment. The tensile strength and the fracture morphology showed no significant change after salt-bath nitriding treatment. The tensile length after fracture,the reduction of cross-section area and impact absorption energy were slightly decreased. The time of resistance to neutral salt spray was 6. 3 fold as high as that of the sample coated with hard chromium. The surface wear scars after wear at high temperature for 190 s were fine and uniform,and the wear weight loss was reduced by 62. 8% as compared to the sample coated with hard chromium. Conclusion The salt-bath nitriding process did not damage the microstructure and mechanical properties of 32Cr2Mo2 NiVNb steel,with only slight decreased in plasticity and toughness indexes,and could significantly improve the corrosion resistance and high-temperature wear resistance of 32Cr2Mo2 NiVNb steel as compared to hard chromium plating. The new salt-bath nitriding process was well suitable for surface treatment of 32Cr2Mo2 NiVNb steel.