侧向送丝光纤激光单道熔覆层组织

Microstructure of single track fiber laser cladding with wire feeding by side

关键词:  激光熔覆  侧向送丝  微观组织  显微硬度

Key words:  laser cladding  wire feeding by side  microstructure  microhardness

摘要:

采用正交试验法在不锈钢表面侧向送丝单道激光熔覆,确定激光功率、扫描速度、送丝速度对熔覆层横截面几何尺寸、宽高比及稀释率影响,找出最佳工艺参数组合并进行组织分析.结果表明,当激光功率为2 000 W,扫描速度为4 mm/s,送丝速度为20 mm/s时可得到稳定良好的熔覆层;熔覆层从结合区到表层晶粒形态依次是平面晶、胞状晶、柱状树枝晶、等轴树枝晶、转向树枝晶;熔覆层组织由γ奥氏体和残余δ铁素体组成,δ铁素体主要成蠕虫状、骨架状和侧板条状分布于奥氏体枝晶间或晶界处;熔覆层显微维氏硬度平均值(195 MPa)与基材(207 MPa)相当且分布相对均匀,热影响区维氏硬度略低(178 MPa).

Abstract:

Laser cladding was performed on the surface of stainless steel with wire feeding by side. To obtain an optimal combination of process parameters, orthogonal test was used to determine the influences of laser power(P), scanning velocity(v_s) and wire feeding speed(v_w) on the cross-section geometry, aspect ratio and dilution rate of cladding track. The results show that the stable and smooth cladding track can be obtained when the combination of process parameters are P=2 000 W, v_s=4mm/s, and v_w=20 mm/s. Grain morphology of the cladding track from the binding to the surface are planar crystal, cellular crystal, columnar dendrites, equiaxed dendrite, steering dendrites. The microstructure of laser cladding track is composed of γ austenite and residual δ ferrite, and the δ ferrite distributed in the austenite grain boundaries or between dendrites with the vermicular, skeletal and lathy morphologies. The average microhardness of the cladding track is about 195 MPa near to the one of substrate(207 MPa), which is evenly distributed, but the microhardness of heat affected zone(178 MPa) is lower than the one of substrate.