超声冲击细化FGH95镍基高温合金激光熔覆层组织

Fining grain of FGH95 nickel-based superalloy laser cladding layer by ultrasonic impact treatment

关键词:  激光熔覆  超声冲击  晶粒细化  镍基高温合金  显微维氏硬度

Key words:  laser cladding  ultrasonic impact treatment  grain fining  nickel-based superalloy  microhardness

摘要:

采用超声冲击工艺对FGH95镍基高温合金激光熔覆层进行处理. 利用金相显微镜分析超声冲击前后激光熔覆层微观组织的变化特征,采用图像分析软件Image-Pro Plus测量晶粒尺寸,并对超声冲击处理前后熔覆层截面的显微维氏硬度进行了对比分析. 结果表明, 超声冲击处理后熔覆层发生塑性变形,并沿深度方向晶粒具有不同程度的细化. 强塑性变形区内位错塞积现象显著,熔覆层组织形成细化的小晶块;次塑性变形区深度范围为0.1~0.25 mm,其微观组织中存在大量细化的树状枝晶;微塑性变形区内等轴晶细化至5.4 μm,细化深度达0.7 mm. 超声冲击处理后熔覆层显微维氏硬度显著增大,表面显微维氏硬度值最大为594.25 HV,相比未经冲击熔覆层提高1.3倍.

Abstract:

FGH95 nickel-based superalloy laser cladding layer was strengthened by ultrasonic impact treatment(UIT). The microstructure of laser cladding with and without UIT was studied by metallurgical microscope, the grain size was calculated by the Image-Pro Plus software, and the sectional microhardness of laser cladding was also analyzed after UIT. Results show that plastic deformation of cladding layer was formed with UIT and the varying degrees of grain refined behavior were obvious in depth direction. Dislocation pile up phenomenon was significant in strong plastic deformation zone with refined small crystal block. Sub-plastic deformation zone was depth range of 0.1-0.25 mm and the microstructure of this zone was refinement tree dendrite. The microstructure of micro-plastic deformation zone was mainly refined equiaxed grains into 5.4μm depth to 0.7 mm. The microhardness of cladding layer was enhanced significantly and the maximum value of surface microhardness was 594.25 HV by 1.3 fold after UIT.