Prasad B Hari, Madhusudhan Reddy G, Das Alok Kumar, Prashanth Konda Gokuldoss
Defence Research & Development Laboratory, Hyderabad 500058, India.
Defence Metallurgical Research Laboratory, Hyderabad 500058, India.
Materials (Basel). 2022 Nov 2;15(21):7708. doi: 10.3390/ma15217708.
The present study describes the laser welding of Co-based superalloy L605 (52Co-20Cr-10Ni-15W) equivalent to Haynes-25 or Stellite-25. The influence of laser welding process input parameters such as laser beam power and welding speed on mechanical and metallurgical properties of weld joints were investigated. Epitaxial grain growth and dendritic structures were visible in the weld zone. The phase analysis results indicate the formation of hard phases like CrFeNi, CoC, FeNi, and CFe in the weld zone. These hard phases are responsible for the increase in microhardness up to 321 HV in the weld zone, which is very close to the microhardness of the parent material. From the tensile strength tests, the ductile failure of welded specimens was confirmed due to the presence of dimples, inter-granular cleavage, and micro voids in the fracture zone. The maximum tensile residual stress along the weld line is 450 MPa, whereas the maximum compressive residual stress across the weld line is 500 MPa. On successful application of Response Surface methodology (RSM), laser power of 1448.5 W and welding speed of 600 mm/min i.e., line energy or heat input equal to 144 J/mm, were found to be optimum values for getting sound weld joint properties. The EBSD analysis reveals the elongated grain growth in the weld pool and very narrow grain growth in the heat-affected zone.
本研究描述了与Haynes-25或司太立合金-25相当的钴基高温合金L605(52Co-20Cr-10Ni-15W)的激光焊接。研究了激光束功率和焊接速度等激光焊接工艺输入参数对接头力学和冶金性能的影响。在焊缝区可见外延晶粒生长和树枝状组织。相分析结果表明,焊缝区形成了CrFeNi、CoC、FeNi和CFe等硬质相。这些硬质相导致焊缝区显微硬度增加至321 HV,这与母材的显微硬度非常接近。拉伸强度试验表明,由于断口区存在韧窝、沿晶解理和微孔洞,焊接试样发生韧性断裂。沿焊缝线的最大拉伸残余应力为450 MPa,而垂直于焊缝线的最大压缩残余应力为500 MPa。成功应用响应面法(RSM)后,发现激光功率为1448.5 W、焊接速度为600 mm/min(即线能量或热输入等于144 J/mm)是获得良好焊接接头性能的最佳值。电子背散射衍射(EBSD)分析表明,焊缝熔池中晶粒呈拉长生长,热影响区晶粒生长非常狭窄。