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date, low carbon 13 pctCr-4 pctNi martensitic stainless steels are mainly used to manufacture hydraulic turbine components, such as turbine runners and guide vanes. For the majority of the assembly and repair work on these relatively large turbine components, conventional fusion welding processes, such as gas metal arc welding (GMAW) and flux core arc welding (FCAW), are commonly applied presently. However, these conventional arc welding processes involve several welding passes to fill the wide groove and, thus, high heat input, which increases distortion and generates large fusion and heat-affected zones. In addition to the high consumable costs related to the filler metal and shielding gas

FATEMEH MIRAKHORLI, Ph.D. Candidate, is with the Mechanical Engineering Department, E´cole de technologie supe´rieure, Montreal, QC H3C 1K3, Canada, and also with the National Research Council Canada-Aerospace, 5145 Decelles Avenue, Montreal, QC H3T 2B2, Canada. Contact e-mail: [email protected] XINJIN CAO, Senior Research Officer, is with the National Research Council Canada-Aerospace, and also Adjunct Professor with the Mechanical Engineering Department, E´cole de technologie supe´rieure. XUAN-TAN PHAM and JEAN-LUC FIHEY, Professors, are with the E´cole de technologie supe´rieure. PRITI WANJARA, Senior Research Officer, is with the National Research Council Canada-Aerospace.  Published with permission of the Crown in Right of Canada pertains to Fatemeh Mirakhorli, Xinjin Cao, and Priti Wanjara. Manuscript submitted August 9, 2015. Article published online April 28, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A

consumption, these welding processes are usually performed in manual or semi-automated mode, which thus imparts a relatively high dependency of the product quality on the operator skills and a long manufacturing time is required for assembly of the component or repair of any defects. Hence, the introduction of advanced welding technologies offers considerable potential to eliminate or minimize these aforementioned issues. Coupling a laser with arc welding, hybrid laser-arc welding (HLAW) is a relatively low heat input joining technology that combines the synergistic qualities of the high energy density laser beam for deep penetration at high welding speeds with the tolerance of arc welding processes for a wide fit-up gap via wire feeding.[1,2] Thus, the two coupled heat sources (laser and arc) in the HLAW process lead to a lower number of welding passes and total heat input, which in turn reduces the weldment area, residual stress, and distortion. Also, as compared to arc welding processes, the reduction in the amount of welding consumables and the higher welding speeds of the HLAW process render lower operational costs and reduced product time-to-market.[1] The combination of these advantages makes the HLAW process especially suitable for assembly of thick gage section components. Previous work by the authors describes the possibility of using HLAW for single-pass welding of CA6NM stainless steel,[3] but the