显微组织对718塑料模具钢蚀刻性能的影响

Effect of Microstructure on Etching Performance of 718 Plastic Mold Steel

在预硬型大截面718塑料模具钢上取样,热处理后得到粒状贝氏体、下贝氏体、回火马氏体、不均匀粒状贝氏体4种组织,采用光学显微镜、扫描电镜、光学轮廓仪、电化学工作站等研究了显微组织对表面蚀刻性能的影响。结果表明:在质量分数35.%NaCl溶液中,不同显微组织试样的耐蚀性能由优到劣的排序为粒状贝氏体、下贝氏体、回火马氏体、不均匀粒状贝氏体;由于组织和碳化物的分布不均匀,不均匀粒状贝氏体组织试样中的相界面增多,导致微电池反应数量增多,腐蚀加快,因此耐蚀性能最差;均匀细小粒状贝氏体组织试样则表现出更好的耐蚀性能。

Samples from pre-hardened large-section 718 plastic mold steel were heat treated,and then got four microstructures of granular bainite,lower bainite,tempered martensite and uneven granular bainite.The effect of microstructure on surface etching performance was studied by using optical microscope,scanning electron microscope,optical profiler,electrochemical workstation,etc.The results show that in 3.5 wt%NaCl solution,the order of different microstructure samples according to corrosion resistance from good to bad was listed as follows:granular bainite,lower bainite,tempered martensite,and uneven granular bainite.Because of the uneven distribution of the structure and carbides,the number of phase interfaces in the sample with uneven granular bainite structure increased,leading to the increase of the number of microbattery reactions and acceleration of the corrosion;therefore the corrosion resistance was the worst.The sample with uniform fine granular bainite structure showed better corrosion resistance.