激光熔覆Ni-Sn共晶合金的组织演变

采用激光熔覆方法制备了 Ni-Sn共晶合金熔覆层, 通过对不同扫描速度下熔覆层的组织特征进行分析, 发现熔覆层组织主要由琢-Ni+Ni3Sn层片共晶组成, 层片间距相比基材明显细化, 并且在熔覆层与基材界面处, 共晶层片基本沿熔覆层沉积方向外延生长, 随着远离基材, 层片共晶生长方向逐渐向激光扫描方向偏转, 在垂直激光扫描方向的熔覆层横截面呈现出类等轴的共晶团组织。随着扫描速度的增加, 熔覆层中的带状组织和顶部的少量非规则共晶团逐渐消失, 共晶层片间距减小。用描述快速共晶生长的 TMK模型对熔覆层底部的共晶层片间距随激光扫描速度的变化规律进行了分析, 实验结果与理论模型基本吻合。

Microstructure Evolution of Ni-Sn Eutectic Alloy in Laser Cladding

Ni -Sn eutectic deposits were prepared by laser cladding with different scanning velocity, and the microstructure ofdeposits were examined. It is found that, the as-deposited microstructure consists mainly of琢-Ni+ Ni3Sn lamellar eutectic, and theeutectic lamellar spacing is refined significantly compared with that of substrate. At the interface between deposits and the substrate,lamellar eutectic grows epitaxially along the deposition direction. With the increase of the distance from the substrate, lamellareutectic tends to grow along the laser scanning direction gradually, which leads to the formation of equiaxed-like eutectic clusters inthe cross section of deposits. As the laser scanning velocity increases, the eutectic lamellar spacing decreases, meanwhile, theanomalous eutectic at the top of deposits and banded structure in the deposits disappear gradually. The relationship between eutecticlamella spacing and laser scanning velocity at the bottom of deposits was further analyzed using TMK models, and the experimentresults shows a reasonable agreement with the models' prediction.