H13钢表面激光选区熔覆Ni-Al金属间化合物涂层的组织与性能

通过控制Ni 基自熔性合金粉末中Al 的含量，在H13 热作模具钢表面分别原位制备了Ni3Al和NiAl 金属间化合物复合熔覆涂层。借助光学显微镜和X 射线衍射仪对不同熔覆涂层的化学组成和物相结构进行了分析。结果表明，四种不同Al 含量的熔覆层均显现出平整致密、无明显缺陷的宏观特征。随着Al 含量的增加，熔覆层显微形貌呈现出底部枝晶区域增加及枝晶逐渐粗化，甚至出现胞状晶的现象。熔覆层在未加入Al 时，其主要物相为Ni3Fe 及（Ni， Cr）固溶体。随着Al 含量的增加，主要物相则由最初的Ni3Al 金属间化合物、（Ni， Cr）固溶体到Ni3Al、NiAl 金属间化合物和（Fe，Cr）固溶体，再到最终Al 含量达到13.9%时的NiAl 金属间化合物和（Fe，Cr）固溶体。同时，Al 含量的提高使得涂层中杂质相减少。熔覆层摩擦系数均低于基体，最高显微硬度为基体的3.5 倍，耐磨性较基体提高了5.8 倍。

Microstructure and property of selective laser cladding Ni-Al intermetallic compound coating on H13 steel surface

In situ Ni3Al and NiAl intermetallic compound composite laser cladding coatings were prepared on H13 hot die steel surface by controlling Al content in the Ni-based self-fluxing alloy powder. The chemical composition and phase structure of the different laser cladding composite coatings were characterized by optical microscopy (OM) and X-ray diffraction (XRD). The results indicate that the four kinds of composite laser cladding coatings all show a smooth, dense and without obvious defects macroscopic morphology. The dendrite region becomes wider and the dendrite size gradually becomes thicker in the laser cladding coatings bottom with the increase of Al content, even a columnar crystal phenomenon can be found. Without Al, the main phase of the composite coating is Ni3Fe and Ni-Cr solid solution. While with the increase of Al content, the main phase changes from Ni3Al intermetallic compound and Ni-Cr solid solution to Ni3Al+NiAl intermetallic compound and Fe-Cr solid solution, and then to NiAl intermetallic compound and Fe-Cr solid, when the Al content increases to 13.9%. At the same time, the impurity phase in laser cladding coating decreases with the increase of the Al content. The cladding coatings friction coefficients are lower than those of the H13 steel substrate. The highest microhardness of the coating increases by 250% and the abrasion resistance increases by 480% respectively.