激光熔覆及反应合成铁-铝金属间化合物覆层的研究

Study of Preparing Laser Cladded Fe-Al Intermetallic Coat

分别以纯Fe3Al粉、铁基合金粉＋铝粉为原料，采用激光熔覆工艺在钢基体表面制备Fe-Al金属间化合物。利用扫描电镜、能谱仪与X衍射实验方法等对熔覆合金层以及与钢基体的结合界面等进行了显微组织与相结构的分析。结果表明，采用这两种原料均可以获得与基体之间良好冶金结合的Fe-Al合金覆层，覆层组织致密，均与基体实现了良好的冶金结合；直接熔覆Fe3Al工艺的覆层存在裂纹现象，而铁基合金粉＋铝粉反应合成工艺的覆层组织含少量孤立微孔隙，但无裂纹缺陷；直接熔覆Fe3Al的覆层组织由粗大的等轴状晶团构成，等轴状晶团内部及晶界由大量极细小的板条状Fe3Al晶粒构成，许多相邻板条晶之间具有一致的晶体取向；反应合成工艺的覆层组织主要由大量细密、均匀的树枝晶构成，树枝晶所含元素的原子比Fe：Al：Ni：Cr：Si大约为55：24：8：8：5。

Two kinds of Fe-Al intermetallic coats are prepared on steel substrate by laser cladding with powders of Fe3Al and mixed powders of Fe-based alloy with Al. The microstructure and phase constitution of the coat and the boundary between coat and substrate are studied with SEM, EDX and X-ray analysis technique. The compact coats jointed metallurgically with the steel are all obtained in two ways, cracks are found in the cladding with powders of Fe3Al and a few pores are found in the synthesize cladding of mixed powders of Fe-based alloy and Al, but no cracks are found in the latter. Cladding microstructure of the former consist of coarse equiaxed grain-groups, which consist of large amount of banding fine Fe3Al grains, some neighbouring banding grains have the similar orientation. The cladding microstructure of the latter is mainly composed of uniformity and fine dendrites, the atom ratio of Fe：Al：Ni：Cr：Si is about 55：24：8：8：5.