粉末冶金组合烧结中空凸轮轴的组织与性能

Microstructure and properties of assembled hollow camshaft prepared by powder metallurgy combined sintering

采用粉末冶金组合烧结技术制备由Fe-Cr-Mo-P-Si-Cu-C凸轮和16Mn钢管为芯轴组成的中空凸轮轴,对凸轮的密度、硬度等物理性能、摩擦磨损性能和微观组织进行测试与分析,研究烧结致密化机理,并与传统凸轮材料球墨铸铁的摩擦磨损性能进行对比。结果表明:Fe-Cr-Mo-P-Si-Cu-C凸轮材料在烧结过程中产生Fe-C-P三元液相,Cr、Mo元素溶解于液相中使得液相量显著增加,促进液相烧结,体积收缩率高达19.1%。凸轮材料的平均密度为7.51 g/cm3,平均硬度(HRC)53.7,与钢制芯轴形成牢固的冶金结合,扭矩高达1 150 N·m,连接可靠性较好;该凸轮材料的硬度与传统球墨铸铁凸轮材料相近,耐磨性是球墨铸铁的3倍,质量减轻35%,满足发动机使用要求。

A new type of hollow camshaft using Fe-Cr-Mo-P-Si-Cu-C as camshaft and 16Mn steel tube as axis was prepared by powder metallurgy combined sintering technology. The density, hardness, friction and wear property, and microstructure of the hollow camshaft were tested and investigated. The sintering mechanism was also explored. The friction and wear property were compared with that of traditional nodular cast iron camshaft. The results show that Fe-Cr-Mo-P-Si-Cu-C metallurgical powder camshaft material can form Fe-C-P ternary liquid during the process of sintering, at the same time Cr and Mo elements dissolves into the liquid phase, resulting in a significant increase of the liquid phase, which can promote the liquid phase sintering, and the shrinkage rate is as high as 19.1%. The sintered density and hardness （HRC） of powder metallurgy camshaft is 7.51 g/cm3 and 53.7 on average. The camshaft can firmly combine with the steel spindle by metallurgical interface forming in the sintering process, whose torque is as high as 1 150 N/m, and the connection reliability is better. The wear resistance of metallurgical camshaft is 3 times of that of traditional nodular cast iron under the condition of the same hardness, which fits the requirements of engine to use.