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长期以来,工业化国家为了延长机械的使用寿命,都把机械的耐磨问题作为重要课题进行研究。到目前为止,世界上公认的最好耐磨镀层是硬铬镀层。虽然硬铬在常温下硬度高,但却存在许多严重缺陷:(1)镀硬铬所必须使用的镀液中含有剧毒的六价铬。这是各国环境保护法律中法定限制的有害物质;(2)硬铬的硬度虽在常温下很高,但随着温度的升高,硬度迅速降低,硬度的热稳定性很差;(3)硬铬的耐腐蚀能力很差,厚度为0.025～0.035毫米的硬铬镀层,经中性盐雾试验12小时,就产生严重锈蚀;(4)由于镀铬液的毒害性,不能用于刷镀,而槽镀铬的均镀能力又很差,致使加工精度稍高的零件镀铬后必须进行
For a long time, industrialized countries in order to extend the service life of machinery, the mechanical wear resistance issues as an important issue to study. So far, the best wear-resistant coatings recognized worldwide are hard chrome coatings. Although hard chromium has high hardness at room temperature, it has many serious defects. (1) Hard chromium plating must contain highly toxic hexavalent chromium in the plating solution. (2) Although the hardness of hard chromium is very high at normal temperature, the hardness decreases rapidly with the increase of temperature, and the thermal stability of hardness is poor. (3) Hard chrome corrosion resistance is poor, the thickness of 0.025 ~ 0.035 mm hard chrome plating, neutral salt spray test 12 hours, to produce serious corrosion; (4) due to the toxicity of chrome plating solution, can not be used for brush plating, The chrome plated plating capacity is very poor, resulting in slightly higher machining accuracy parts must be chrome plated