硝酸镧浓度对齿轮钢表面锰系复合磷化膜性能的影响

Effect of Lanthanum Nitrate Concentration on Properties of Manganese Composite Phosphating Films on Surface of Gear Steel

为进一步改善锰系复合磷化膜的耐磨性能和耐腐蚀性能,从而为齿轮钢提供更好的抗磨损和腐蚀防护作用,选用硝酸镧作为促进剂添加到磷化液中,在齿轮钢表面制备锰系复合磷化膜。研究了硝酸镧浓度对锰系复合磷化膜的微观形貌、聚四氟乙烯(PTFE)颗粒质量分数、厚度、硬度、耐磨性能和耐腐蚀性能的影响。结果表明:硝酸镧浓度为60 mg/L时制备的锰系复合磷化膜晶粒细化,致密性较好,PTFE颗粒质量分数、厚度和硬度分别达到6.2%、11.8μm、310.4 HV,表现出优良的耐磨性能和耐腐蚀性能。该锰系复合磷化膜的摩擦系数和磨损失重相比于齿轮钢都降低了30%,腐蚀电流密度相比于齿轮钢降低了近两个数量级,可以为齿轮钢提供更好的抗磨损和腐蚀防护作用。在一定范围内硝酸镧浓度增加促使锰系复合磷化膜的晶粒细化,致密性逐步改善,同时促进PTFE颗粒伴随着磷化膜沉积起到自润滑减摩作用,有效地改善锰系复合磷化膜的耐磨性能。另外,PTFE颗粒伴随着磷化膜沉积较好地填充晶粒间空隙,使锰系复合磷化膜发生电化学腐蚀反应的难度增加,腐蚀倾向减弱。

In order to further improve the wear resistance and corrosion resistance of manganese composite phosphating film,so as to provide better anti-wear and corrosion protection for gear steel,the manganese composite phosphating film on the surface of gear steel was prepared by adding lanthanum nitrate as accelerator into the phosphating solution. The effects of lanthanum nitrate concentration on the microstructure,mass fraction of polytetrafluoroethylene(PTFE)particles,thickness,hardness,wear resistance and corrosion resistance of manganese composite phosphating films were studied. The results showed that when the lanthanum nitrate concentration was 60 mg/L,the obtained manganese composite phosphating film had finer grains and better compactness. And the mass fraction of PTFE particles,thickness and hardness reached 6.2 %,11.8 μ m and 310.4 HV,respectively,showing excellent wear resistance and corrosion resistance. The films can provide better wear and corrosion protection for gear steel,the friction coefficient and wear loss were reduced by 30 % compared with that of gear steel,and the corrosion current density was reduced by nearly two orders of magnitude compared with that of gear steel. The increase of lanthanum nitrate concentration in a certain range can promote the grain refinement of the manganese composite phosphating film,and the compactness was gradually improved. Moreover,lanthanum nitrate promoted PTFE particles to fill the intergranular gaps accompanied by phosphating film deposition,which can effectively hinder the corrosion,reduce the corrosion tendency and improve the wear resistance of manganese phosphating film.