Metallurgical and Materials Transactions B

, Volume 47, Issue 6, pp 3245–3256 | Cite as

Post-weld Tempered Microstructure and Mechanical Properties of Hybrid Laser-Arc Welded Cast Martensitic Stainless Steel CA6NM

  • Fatemeh Mirakhorli
  • Xinjin Cao
  • Xuan-Tan Pham
  • Priti Wanjara
  • Jean-Luc Fihey


Manufacturing of hydroelectric turbine components involves the assembly of thick-walled stainless steels using conventional multi-pass arc welding processes. By contrast, hybrid laser-arc welding may be an attractive process for assembly of such materials to realize deeper penetration depths, higher production rates, narrower fusion, and heat-affected zones, and lower distortion. In the present work, single-pass hybrid laser-arc welding of 10-mm thick CA6NM, a low carbon martensitic stainless steel, was carried out in the butt joint configuration using a continuous wave fiber laser at its maximum power of 5.2 kW over welding speeds ranging from 0.75 to 1.2 m/minute. The microstructures across the weldment were characterized after post-weld tempering at 873 K (600 °C) for 1 hour. From microscopic examinations, the fusion zone was observed to mainly consist of tempered lath martensite and some residual delta-ferrite. The mechanical properties were evaluated in the post-weld tempered condition and correlated to the microstructures and defects. The ultimate tensile strength and Charpy impact energy values of the fully penetrated welds in the tempered condition were acceptable according to ASTM, ASME, and industrial specifications, which bodes well for the introduction of hybrid laser-arc welding technology for the manufacturing of next generation hydroelectric turbine components.


Welding Austenite Martensite Welding Speed Charpy Impact 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



Temperature at which austenite begins to form during heating


Base metal


Electron beam welding


Flux core arc welding


Fusion zone


Gas metal arc welding


Gas tungsten arc welding


Heat-affected zone


Hybrid laser-arc welding


Martensite finish temperature


Martensite start temperature


Optical microscopy


Partially melted zone


Post-weld heat treatment


Scanning electron microscopy



The authors are grateful to Alstom, Hydro-Québec, Aero 21 Program of the National Research Council of Canada and National Science and Engineering Research Council of Canada (NSERC) for the financial supports. The authors also wish to thank E. Poirier and X. Pelletier of NRC Aerospace for their technical assistance during welding and metallographic preparation.


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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2016

Authors and Affiliations

  • Fatemeh Mirakhorli
    • 1
    • 2
  • Xinjin Cao
    • 1
    • 2
  • Xuan-Tan Pham
    • 1
  • Priti Wanjara
    • 2
  • Jean-Luc Fihey
    • 1
  1. 1.Mechanical Engineering DepartmentÉcole de technologie supérieureMontrealCanada
  2. 2.National Research Council Canada–AerospaceMontrealCanada

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