Abstract
A novel repair strategy based on decoupled heat source for increasing the productivity of wire-assisted pulsed laser cladding of the γ’-precipitation strengthening nickel-base superalloys Inconel 738 low carbon (IN 738 LC, base material) and Haynes 282 (HS 282, filler material) is presented. The laser beam welding process is supported by the hot-wire technology. The additional energy is utilized to increase the deposition rate of the filler material by increasing feeding rates and well-defining the thermal management in the welding zone. The simultaneous application of laser pulse modulation allows the precise control of the temperature gradients to minimize the hot-crack formation. Accompanying investigations such as high-speed recordings and numerical simulations allow a generalized statement on the influence of the adapted heat management on the resulting weld seam geometry (dilution, aspect ratio and wetting angle) as well as the formation of hot-cracks and lack of fusion between base and filler material. Statistical analysis of the data—the input parameters like laser pulse energy, pulse shape, hot-wire power and wire-feeding rate in conjunction with the objectives like dilution, aspect ratio, wetting angle and hot-cracking behavior—revealed regression functions to predict certain weld seam properties and hence the required input parameters.
Highlights
Nickel-base superalloys are the preferential material for stator and rotor blades in stationary gas turbines due to their outstanding high temperature, creep and fatigue strength as well as toughness, impact resistance and resistance to hot gas corrosion, especially since they retain their strength up to 90% of their melting temperature [1,2]
Since the hot-wire power has no remarkable effect on the weld seam geometry, all data were averaged over the applied hot-wire power to gain more clarity of the effect of the main input parameters pulse energy, pulse shape and wire-feeding rate, by combining all data in one diagram for each objective, i.e., dilution, wetting angle and aspect ratio
The decoupling of heat source from the laser beam into the filler material was successfully implemented by the hot-wire technology
Summary
Nickel-base superalloys are the preferential material for stator and rotor blades in stationary gas turbines (commonly IN 738 LC) due to their outstanding high temperature, creep and fatigue strength as well as toughness, impact resistance and resistance to hot gas corrosion, especially since they retain their strength up to 90% of their melting temperature [1,2]. Wire If melting deposition rate, the process has so far only been implemented industrially for repairing it is possible to extract heat quantities from the pulsed laser beam welding process individual blades. The hot-wire temperature for multilayer surface repair welding, where both dilution and wetting angle have to be minimized to should not exceed the softening or plasticizing temperature of the filler material, i.e., larger than 900 realize large beads with defect-free fusion. The influence of the hot-wire technology towelding the laserprocess pulse and transfer them to the filler material, it might be feasible to increase the deposition rate and welding energy, the pulse shape and the wire-feeding rate onto the geometrical weld seam properties as well speed maintaining or reducing the dilution of the base material.
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