激光表面熔覆层凝固组织特征形成过程

Study on the formation features of solidification microstructure for laser cladding layer

试验研究了激光熔覆层的凝固特征和组织形成规律。结果表明:熔覆层不同位置的凝固特征参数不同。熔覆层底部属于典型的平面外延生长组织,且枝晶粗大;而顶部是较规则的树枝状共晶组织;中部为细小的胞晶和柱状晶;且晶体生长受结晶学各向异性影响。熔覆层组织晶粒形核的非均匀形核特征显著。熔覆层微区成分存在着不均匀性,不同元素沿晶间偏析(富集)。

The investigation on the solidification features and formation law of microstructure for laser cladding layer has been carried out.It is shown that there are different solidification parameters for different position in cladding layer.The microstructure at the cladding layer bottom was the typical extension growth on plane basis,the dendrite crystal is coarser.The microstructure at the top and middle was the regular pine tree eutectic crystal and small cell and column crystal,respectively.The crystalline anisotropy was a main factor to influence the crystal growth form.The grain nucleation has obvious feature of heterogeneous nucleation in microstructure cladding.The results also show that the components in microzone of the cladding layer are not uniform.The different elements segregate along crystalline axis or interdendritic result in the non uniform microstructure.