Abstract
Welding by laser beam is a method for creating deep and narrow welds with low influence on the surrounding material. Nevertheless, the microstructure and mechanical properties change, and highly alloyed materials are prone to segregation. A new promising approach for minimizing segregation and its effects like hot cracks is introducing ultrasonic excitation into the specimen. The following investigations are about the effects of different ultrasonic amplitudes (2/4/6 µm) and different positions of the weld pool in the resonant vibration distribution (antinode, centered, and node position) for bead on plate welds on 2.4856 nickel alloy round bars (30 mm diameter) with a laser beam power of 6 kW. The weld is evaluated by visual inspection and metallographic cross sections. The experiments reveal specific mechanisms of interaction between melt and different positions regarding to the vibration shape, which influence weld shape, microstructure, segregation, cracks and pores. Welding with ultrasonic excitation in antinode position improves the welding results.
Highlights
Nickel alloys with an addition of about 20% chromium show high corrosion resistance and high strength at elevated temperatures, so they are commonly used for high-temperature applications and in corrosive environments, as example for fan blades in turbines or for parts in chemical plants [1]
Segregated alloying elements are missing in the residual material, which changes its properties like corrosion resistance in the case of chromium [2]
4), depends strongly on position according to both the vibration distribution and vibration amplitude
Summary
Nickel alloys with an addition of about 20% chromium show high corrosion resistance and high strength at elevated temperatures, so they are commonly used for high-temperature applications and in corrosive environments, as example for fan blades in turbines or for parts in chemical plants [1].There are several trade names for this material group like Inconel, Chronin or Nicrofer.Welding of highly alloyed nickel leads to similar problems as in welding stainless steel. Nickel alloys with an addition of about 20% chromium show high corrosion resistance and high strength at elevated temperatures, so they are commonly used for high-temperature applications and in corrosive environments, as example for fan blades in turbines or for parts in chemical plants [1]. There are several trade names for this material group like Inconel, Chronin or Nicrofer. Segregation is likely to occur due to a high amount of alloying elements. Those can form lately solidifying phases between the primary grains, and effect hot cracking [1]. Segregated alloying elements are missing in the residual material, which changes its properties like corrosion resistance in the case of chromium [2]
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