稀土对渗铝层/基体界面空洞生长和抗高温剥落性能的影响

通过高温氧化实验以及测量空洞平均直径和形核数量随氧化时间的变化,研究稀土对渗铝层抗高温剥落性能和渗铝层/基体界面空洞生长的影响,并与渗纯铝试样进行了比较.结果表明:渗铝层/基体界面空洞的生长可划分为快速生长和稳定生长两个阶段;但当渗稀土铝后,空洞生长速度比渗纯铝试样降低约1/3;稀土可抑制界面空洞的形核和生长,阻止空洞聚集成波浪线状空洞带和线状裂纹,提高渗铝钢的抗高温剥落性能;热浸镀稀土铝后,试样表面自由铝层减薄,从而降低了高温下渗铝层/基体界面铝的浓度梯度,这是稀土抑制空洞形核和生长的主要原因.

Effects of rare earth on formation of voids at interface of aluminized coating/steel matrix and spalling resitance

The effects of rare earth(RE) elements on the void formation in aluminized coating and the spalling resistance of aluminized steel were investigated through cyclic oxidation test and measurement of the variations of the average size and the number of the voids with oxidation time,and compared with those of plain aluminized steel without RE.The results show that the growth of the voids can be divided into two stages of fast growth and stable growth,and the growth speed of the void of the RE-added aluminized coating decreases by about 1/3,in comparison with that of the plain aluminized coating.RE addition can restrain the formation and aggregation of voids and subsequently improve the oxidation and spalling resistance.The main reason why RE restrains the formation and the growth of voids is the concentration gradient of aluminum decreases at high temperature due to the decrement of the thickness of pure aluminum coating after hot dip RE-aluminizing.