不同粉末对等离子弧喷焊DZ125合金显微组织的影响

Effect of different powders on microstructure of DZ125 alloy by plasma arc spray welding

采用等离子弧喷焊技术在定向凝固DZ125合金表面制备钴基与镍基合金熔覆层。结果表明,熔覆层在基材的结合界面处形成的是外延生长的柱状晶组织,随着温度梯度G减小,成分过冷程度增加,组织发生了柱状晶向等轴晶的转变。凝固时固液界面前移,使得温度梯度降低,在相同条件下,Ni基合金比Co基合金更易转化为等轴晶,形成的柱状晶更少。Co基合金与Ni基合金熔覆层硬度自基材到表面呈上升趋势,相较于基材的组织,熔覆层的柱状晶组织更为细小,硬度更高,熔覆层的等轴晶硬度高于柱状晶。

Cobalt-based and nickel-based alloy cladding layers were respectively prepared by plasma arc welding on directionally solidified DZ125 alloy surface.Results showed that columnar grains of the cladding layer at the bonding interface between the cladding layer and the substrate were epitaxial.With the decrease of temperature gradient G and the increase of constitutional supercooling degree,the columnar grains became equiaxed grains.During solidification process,the solid-liquid interface moved forward,which resulted in the decrease of temperature gradient.Thus,under the same condition,Ni-based alloy was easier to convert into equiaxed grains than that of Co-based alloy,while in turn less columnar crystals were formed.The microhardness of the cladding layers of Co-based and Ni-based alloy gradually increased from the substrate to their surfaces.Columnar grains of the cladding layer were finer and the hardness were higher,when being compared with those of the substrate.Hardness of equiaxed grains of the cladding layer was higher than that of columnar grains.