等离子熔覆Ni-Cr合金强化粮油食品机械螺杆的研究

STUDY ON THE PLASMA SURFACING Ni-Cr CLADDING FOR THE SPECIAL AXES IN THE SCREW MECHANISM

采用等离子熔覆技术在粮油食品机械螺杆基材40Cr合金钢表面等离子熔覆Ni-Cr合金涂层,研究了熔覆层的组织特征和显微硬度.实验结果表明:等离子熔覆层与基体的结合面是由等轴晶构成的,熔覆层与基体呈现良好的冶金结合状态;熔覆层中部分布着沿逆热流方向生长的排列较规则的枝晶组织;熔覆层表层是细小的枝晶组织.当扫描速度一定时,较高的熔覆功率下的熔覆层内的枝晶和等轴晶得到细化.熔覆层的显微硬度呈梯度过渡到基体,熔覆层外层硬度值最高,在结合面附近硬度出现显著的变化,但熔覆功率对熔覆层硬度的影响并不显著.

The Ni-Cr cladding was coated on the 40Cr alloy by the PTA （plasma Transferred arc） surfacing process. The microstructures and microhardness of the coating were investigated. It was suggested that the coating is well bonded with the 40Cr alloy and the intreface consists of the isometric crystal. The microstructures vary from relatively regular dentritic crystal in the middle of the coating to fine equiaxed crystal near the top of the coating. The dentritic crystal and the equiaxed crystal of the coating were fined on the high power with the definite rates. The hardness of the coating reduced sequentially in the form of the gradient. The hardness near the top of the coating was the highest and the hardness nearby the intreface changed observably. But the effect of the power on the hardness was not prominent.