热浸镀镧铝钢的高温耐热行为研究

Heat Resistance Behavior of Hot Dip Aluminized Steel with Rare Earths

在20碳钢上分别制备了热浸镀纯铝和镧铝涂层。经过900℃×6h的扩散处理后，研究了涂层的抗氧化性能和组织形貌变化。结果表明：热浸镀镧铝试样表面的纯铝层厚度比热浸镀纯铝试样减少25％～35％；经扩散处理后，在800℃氧化的前40h，热浸镀纯铝试样氧化动力学曲线符合抛物线规律，40h后，氧化动力学曲线呈直线。在整个氧化期间，热浸镀镧铝试样的氧化动力学曲线都符合抛物线规律，且抗高温剥落性能同样优于热浸镀纯铝试样。组织形貌分析表明，镧抑制了扩散和高温氧化过程中扩散层／基体界面孔洞的形成和聚集，阻止了扩散层的内氧化。分析了镧对镀铝钢高温耐热行为的影响机理。

The pure aluminized coating and La-aluminized coating on 20 carbons steel was prepared by hot dip aluminizing method, respectively. The oxidation resistances and microstructures of the coatings were investigated after diffusion treatment at 900℃ for 6h. The results show that,the thickness of the surface coating of the hot dip La-aluminized specimens decrease by about 25%-35% than that of the hot dip pure aluminized specimens. After diffusion treatment, the oxidation kinetics curve of pure aluminized coating accords with a parabola growth rule before 40h and then presents a linear growth rule with a higher oxidation rate after 40h. The oxidation kinetic curve of La-aluminized coating obeys a parabola growth rule during the whole oxidation and its mass increase is less than that of pure aluminized coating. La addition can restrain the formation and aggregation of voids and subsequently improve the resistances to oxidation and spalling. The mechanism of the La effect on the heat resistance behavior of hot dip aluminized steel is also discussed.