热处理对FeAl-Cr_3C_2复合涂层微观结构的影响

Influence of Heat Treatment on Microstructure of Composite Coatings of FeAl-Cr_3C_2

利用超音速火焰喷涂(HVOF)方法在304钢上制备了厚度约为30μm的Fe40Al-50%Cr3C2涂层,采用XRD,SEM/EDS分析其在阶梯温度退火后的微观结构演化行为。退火前涂层的表面十分粗糙,成分分布很不均匀,主要由Fe、Al和Fe-Al金属间化合物以及少量的Fe、Al的氧化物组成,涂层的最外层存在较多大块Fe颗粒,靠近基体部分存在少量的Al颗粒。经过真空退火处理之后,涂层的成分均匀性有了很大的改善,但是涂层中的一些孔洞依然存在。随着真空退火温度从700℃升高到900℃,涂层中大块Fe、Al颗粒逐渐消失,Fe、Al扩散反应更加充分,涂层中形成了更多的Fe-Al金属间化合物。

Composite coatings of Fe40Al-50%Cr3C2 with the thickness of 30 μm were prepared by high velocity oxygen-fuel （HVOF） technology on 304 steel. The change of its microstructure by heat treatment at different temperatures was studied by means of XRD and SEM/EDS. The surface of the coating is very rough and the element distribution is inhomogeneous before the heat treatment. The composition of the coating is mainly composed of Fe, Al, intermetallics plus a little oxide of Fe and Al. A large amount of particles of Fe with big size are present in the outer layer, while a few particles of Al are present in the inner layer. The homogeneity of the coating has great change after vacuum annealing, though some holes still exist in the coating. With the increase of the annealing temperature from 700 ℃ to 900 ℃, the pure Fe and Al particles of big size disappear gradually due to their full diffusion and thereby formation of more intermetallics.