激光沉积修复单道多层DZ125双级时效热处理组织与性能

Microstructure and Properties of Two-stage Aging Heat Treated Single Multilayer DZ125 After Laser Deposition Repair

通过在DZ125铸造基体上沿纵向进行激光沉积单道多层实验,分析了DZ125沉积态与双级时效热处理试样的组织和性能。结果表明:沉积态修复区组织从底部到顶部分别为平面晶、柱状晶和等轴晶组织,修复区主要为MC碳化物,热影响区因热量的输入,MC分解为M23 C6;与沉积态组织相比,双级时效热处理后,修复区组织形成了新的晶界,部分MC碳化物分解为M6C与M23C6,γ’相尺寸略有增大,为600~800 nm,分布均匀;热影响区碳化物尺寸略有减小,γ’相尺寸增大,呈立方体形状;双级时效热处理修复试样在1000℃下的抗拉强度为516 MPa、屈服强度为386 MPa,可分别达到铸件的89.7%和97.7%,延伸率为13.6%,达到铸件的43.9%;热处理后修复试样的平均硬度为4730 MPa(HV0.3),高于沉积态试样平均硬度4330 MPa(HV0.3),且热处理态与沉积态试样沿修复区、热影响区到基体硬度呈降低趋势。

The microstructure and properties of DZ125 samples(as-deposited and two-stage aging heat treated)were analyzed by laser deposition single multi-layer experiments on the casting substrate along the longitudinal direction of DZ125.The results show that the microstructure of the sedimentary repair area is planar crystal,columnar crystal and equiaxed crystal structure from the bottom to the top.The repaired area is mainly MC carbide.The heat affected zone will be decomposed into M23C6 by MC due to the input of heat.Compared with the as-deposited microstructure,after the two-stage aging heat treatment,a new grain boundary is formed in the repaired area,and some MC carbides are decomposed into M6 C and M23C6,and theγ’phase size is slightly increased,about 600~800 nm,and the distribution is uniform.The size of the carbides in the heat-affected area is slightly reduced,the size of the y’phase is increased,and it is cubic.The tensile strength of the two-stage aging heat treatment specimen is 516 MPa at 1000℃,and the yield strength is 386 MPa,which is 89.7%and 97.7%of that of the casting,respectively.The elongation rate is 13.6%,reaching 43.9%of that of the casting;the average hardness of the repaired sample after heat treatment is 4730 MPa(HV0.3),which is higher than the average hardness of the as-deposited sample 4330 MPa(HV0.3).The hardness of the heat-treated and the deposited samples along the repair zone and the heat-affected areas to the matrix tends to be decreased.