W360热作模具钢渗硫的渗层组织及抗擦伤性能

目的基于硫化处理能够减弱摩擦界面"咬合力"的特点,通过低温液体工艺对Bohler W360热作模具钢进行了渗硫处理,以期进一步改善模具抗擦伤性能。方法采用硫粉、氢氧化钠和去离子水三元碱性渗剂体系,设计不同的硫含量,以研究硫浓度对渗层组织的影响,利用SEM-EDS和XRD对渗硫层形貌和结构进行分析,通过洛氏硬度计和MRH-3A高速环块磨损试验机,分别对渗硫前后材料的表面硬度和摩擦磨损性能进行检测和评价。结果通过低温液体渗硫工艺,W360模具钢表面渗硫层因硫含量不同而分别形成了"板结"结构和"微颗粒+空隙"结构,XRD结果表明渗硫层由Fe S和Fe S2构成。硬度测试显示,渗硫后,W360模具钢的表面硬度未发生变化(52~53HRC),与原始硬度一致。但摩擦磨损试验数据表明,硫化处理可以显著降低摩擦初期W360钢的摩擦系数,磨损失重和磨痕宽度等数据揭示硫质量分数为1.5%时,抗擦伤性最佳。结论低温液体渗硫工艺通过降低模具钢表面摩擦系数,能够提高材料的抗擦伤性能,渗剂中硫元素的含量对渗层组织和抗擦伤性能有显著的影响。

Effects of Sulfurizing Treatment on Microstructure and Scratch Resistance of W360 Hot Work Die Steel

The work aims to further improve scratch resistance of moulds by sulfidizing Bohler W360 hot work die steel in low temperature liquid process as sulfurizing treatment can reduce "bite force" of frictional interface. Provided with alkaline sulfurizing agent system consisting of sulfur powder, sodium hydroxide and deionized water, effects of sulfur concentration on structure of sulfurizing layer by designing different sulfur content (mass fraction). Morphology and structure of the sulfurizing layer were analyzed by using SEM-EDS and XRD. Surface hardness as well as friction and wear properties of the material before and after sulfurization were tested and evaluated by using Rockwell hardness tester and MRH-3A high speed ring-on-block abrasion tester. By adopting low temperature liquid sulfurizing process, a "hardened" structure and "microparticles+interspace" structure took shape on W360 die steel as a result of different sulfur mass fractions. XRD results showed that the layer consisted of FeS and FeS2. The hardness test showed that the surface hardness of W360 die steel did not change (52~53HRC) after sulfurization, which was consistent with the original hardness. However, friction and wear test data showed that sulfurization could significantly reduce friction coefficient, wear loss weight and grinding crack width of the W360 steel at early stage of friction. The data showed that the scratch resistance was best when the sulfur mass fraction was 1.5%. Low temperature liquid sulfurizing process can improve scratch resistance of the material by reducing friction coefficient of mould steel. Mass fraction of sulfur element in sulfuring agent has a significant effect on microstructure and scratch resistance.