回火工艺对含铜塑料模具钢在中性氯化钠溶液中腐蚀行为的影响

Effect of Tempering Treatment on Corrosion Behavior of Cu-bearing Plastic Mold Steel in Neutral Sodium Chloride Solution

采用场发射透射电子显微镜、扫描电子显微镜和白光干涉仪等分析手段对比研究了含铜塑料模具钢4Cr13Cu及4Cr13在3.5%(质量分数)NaCl中性溶液中的腐蚀行为。结果表明,4Cr13Cu在250℃回火条件下的耐蚀性最佳。600℃高温回火促进了4Cr13Cu纳米级富铜相的析出,使得4Cr13Cu钝化膜施主密度比4Cr13高约12.4%,钝化膜稳定性降低。腐蚀初期,点蚀沿深度和广度方向开始发展,紧接着向深度方向发展至560~660μm范围,最后转向广度方向。而表面距离较近的小点蚀长大、合并,逐步形成了大尺寸点蚀坑。

The corrosion behavior of Cu-bearing plastic mold steels 4Cr13Cu and 4Cr13 in 3.5wt%NaCl neutral solution was investigated by transmission electron microscope(TEM),scanning electron microscope(SEM)and white-light interferometer.The results indicate that it is capable of 4Cr13Cu tempered at 250℃to acquire a better corrosion resistance.The nano-scale Cu-rich precipitates of 4Cr13Cu tempered at 600℃increase the donor density of the passive film by about 12.4%compared with 4Cr13,and reduce the stability of passive film.In the early stage of corrosion process,the pits of 4Cr13Cu begin to grow both horizontally and vertically,then propagate preferentially towards a vertical direction with a depth range of 560—660μm.Finally,the pits expand to horizontal direction.Small pitting in close proximity to the surface grows and merges,gradually forming large size pitting pits.