35CrMo钢热浸镀铝工艺研究

目的通过研究热浸镀铝温度和时间对35Cr Mo钢镀层的影响,从而优化工艺,获得优良的铝合金镀层。方法设置5组温度梯度(700~780℃)和5个时间节点(90~450 s),对35Cr Mo钢进行热浸镀铝工艺研究,制备35Cr Mo钢热浸镀铝镀层。利用SEM观察镀层的组织形貌及其合金元素组成等,并通过显微硬度计测定镀层的厚度。结果热浸镀铝时,钢基体和铝液发生一系列冶金反应,钢镀层明显分为合金层和纯铝层。在720~760℃条件下,浸镀180~360 s时,镀层质量良好,分布均匀,厚度适宜,且没有孔洞、裂纹和漏镀现象。SEM线扫数据表明,铝层和合金层的元素构成和相对比值并不会随工艺参数的变化而改变。在180~450 s之间浸镀时,合金层的显微硬度值均能达到750 HV以上。结论在热浸镀过程中,温度和时间对镀层的厚度、组织和力学性能的影响显著,通过优化热浸镀铝工艺参数,可以改善镀层的质量。

Hot-dip Aluminizing Technology of 35CrMo Steel

The work aims to improve technology and obtain excellent aluminium alloy coating by studying effects of hot-dip aluminizing temperature and time on coating of 35CrMo steel. Five temperature gradients (700~780 ℃) and five time nodes (90~450 s) were set. The 35CrMo hot-dip aluminium-plated coating was prepared by studying hot-dip aluminizing technology of 35CrMo steel. Microstructure of the coating, composition and constitutes of alloy elements were observed with scanning electron microscope (SEM). Thickness of the coating was measured with microhardness tester. A series of metallurgical reac-tions occurred in the steel matrix and aluminum liquid during the hot dip aluminizing process. The steel coating consisted of alloy layer and pure aluminum layer. After being hot dipped for 180~450 s at 720~760 ℃, the coating featured in high quality, uni-form distribution and suitable thickness, and was free from holes, cracks and leakage. The results of SEM line scanning showed that element composition and relative ratio of aluminum and alloy layer didn't change as a function of process parameters. Mic-rohardness values could reach over 750HV when dipping duration was 180 s to 450 s. In hot dipping process, temperature and time have significant influence on thickness, microstructure and mechanical properties of the coating, and coating quality can be improved by optimizing the process parameters of hot-dip aluminizing.