单因素实验法确定两种软磁合金镀铬的最佳工艺条件

Optimal chroming conditions of two soft magnetic alloys as determined by one-factor experimental method

背景:目前主要通过镀铬法提高软磁合金的抗腐蚀性能。目的:采用单因素实验法确定铁铬钼软磁合金和铁镍软磁合金表面镀铬的最佳工艺条件,提高其抗腐蚀能力。方法:铸造20 mm×20 mm×2 mm的方片状铁铬钼合金和铁镍合金各12片,表面经磨光、抛光、活化剂活化后进行镀铬,采用单因素实验法,选因素为电镀类型(分为6价铬和3价铬)、电流密度(15,20,25,35,40,45 A/dm2)和电镀时间(30,40,60 min),考查指标为镀层硬度和厚度,硬度和厚度值越大镀层的耐腐蚀性越强。扫描电子显微镜观察最佳工艺条件下制备的镀层形貌。结果与结论:两种软磁合金表面的6价铬镀层硬度和厚度均大于3价铬镀层,且6价铬镀层相对更均匀,说明电镀6价铬可以明显提高铁镍软磁合金和铁铬钼软磁合金的耐腐蚀性。当基材为铁铬钼软磁合金时,电镀6价铬的最佳工艺为电流密度45 A/dm2,电镀时间为60 min;电镀3价铬的最佳工艺为电流密度20 A/dm2,电镀时间为30 min。当基材为铁镍软磁合金时,电镀6价铬的最佳工艺条件为电流密度35 A/dm2,电镀时间为60 min;电镀3价铬的最佳工艺条件为电流密度20 A/dm2,电镀时间为40 min。

BACKGROUND： Chroming can improve the corrosion resistance of soft magnetic alloys. OBJECTIVE： To identify the optimal chroming conditions of two soft magnetic alloys,Fe-Cr-Mo and Fe-Ni,so as to improve their corrosion resistance. METHODS： Twelve pieces of square-shaped Fe-Cr-Mo and Fe-Ni soft magnetic alloys were casted in the size of 20 mm×20 mm×2 mm. After sanding and polishing,chrome plating was performed on these specimens and the coating thickness and hardness were measured. The selection factors included electroplate type（hexavalent chromium and trivalent chromium）,current density（15,20,25,35,40,45 A/dm^2） and electroplating time（30,40,60 minutes）. The optimal chroming conditions were determined by one-factor experimental method and the chrome plating was observed under a scanning electron microscope. RESULTS AND CONCLUSION： Cr^6＋ coating was significantly better than Cr^3＋ coating in the aspects ofhardness,thickness and uniformity,indicating Cr^6＋ coating can significantly improve the corrosion resistance of Fe-Cr-Mo and Fe-Ni alloys. For Fe-Cr-Mo soft magnetic alloy,the optimal conditions of Cr^6＋ coating were as follows： current density of 45 A/dm^2 and electroplating time of 60 minutes; the optimal conditions of Cr^3＋ coating were as follows： current density of 20 A/dm^2 and electroplating time of 30 minutes. For Fe-Ni soft magnetic alloys,the optimal conditions of Cr^6＋ coating were as follows： current density of 35 A/dm^2 and electroplating time of 60 minutes; the optimal conditions of Cr^3＋ coating were as follows： current density of 20 A/dm^2 and electroplating time of 40 minutes.