采用X射线衍射、SEM、EDXS及显微硬度等方法, 研究了光束堆焊Ni, Al 混合粉末制备的金属间化合物涂层的成形和微观组织特征. 结果表明, 堆焊层的成形与堆焊材料的比热容量和熔点有关. 采用Al含量(原子分数)高于50%或不超过25%的堆焊材料, 均可获得成形良好的光束堆焊层, 但Al含量过高将使堆焊金属的致密度降低. 当堆焊材料中Al含量为 50%--75%时, 堆焊层全部由金属间化合物(Al1.1Ni0.9, Al3Ni2和Al3Ni)组成；当采用富Ni 堆焊材料(不超过25%Al)时, 堆焊层中将析出较多的γ-Ni固溶体, 得到由γ-Ni和Ni3Al金属间化合物组成的显微组织；而采用富Al 堆焊材料(80%Al)将导致堆焊层中析出大量α-Al, 其显微组织为在α-Al+(α-Al+Al3Ni)亚共晶基底上分布有Al3Ni2金属间化合物相.
The formation and microstructure of intermetallic surfacing layers acquired by light beam heating Ni and Al mixed powder were investigated by means of X-ray diffraction, SEM, EDXS and microhardness. The results show that the formation of surfacing layers is related to the heat capacity and melting point of surfacing materials. When the surfacing materials with more than 50%Al (atomic fraction) or not more than 25%Al are used, the surfacing layers with good formation can be obtained. However, too high Al content results in the decrease of the densification of surfacing layer. When the surfacing materials contain 50%--75%Al, the surfacing layers entirely consist of Ni-Al intermetallics (Al1.1Ni0.9, Al3Ni2, Al3Ni). When the surfacing material is rich in Ni (not more than 25%Al), the microstructure is composed of γ-Ni matrix and Ni3Al intermetallic. Adopting the surfacing material rich in Al (80%Al) leads to the precipitation of a lot of α-Al, and the microstructure consists of Al3Ni2 intermetallic precipitated on hypoeutectic matrix composed of the primary α-Al and the eutectic of α-Al+Al3Ni.
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