Influence of oxidation on the cracks of DZ125L nickel-based superalloy thin-walled parts in laser metal direct forming

Purpose - The purpose of this paper is to investigate the influence of the oxidation on the cracks of DZ125L nickel-based superalloy thin-walled parts in laser metal direct forming (LMDF). Design/methodology/approach - Thin-walled cylinders were fabricated in protective atmosphere with different oxygen contents in order to reveal the influence of oxidation on the morphology of cracks. The influence of oxidation on the cracks was investigated in detail by measuring the wall thicknesses of cylinders, the residual stress in the top surface of the cylinders and the composition of the cracks. Finally, the validity of the results was verified by fabricating a thin-walled turbine blade in protective atmosphere. Findings - The experimental results showed that wall thickness fluctuation of cylinders, unequal residual stress distribution of cylinders and the oxides in the crack were all the critical factors which led to crack of DZ125L thin-walled parts. Thin-walled turbine blades with no cracks can be fabricated when the oxygen content was about less than 150 ppm in protective atmosphere. Research limitations/implications - The appropriate oxygen content in protective atmosphere is helpful for fabricating thin-walled parts of nickel-based superalloy like DZ125L, and the results can show what will happen at different oxygen levels. Moreover, the results show that the cracks can be eliminated as the oxygen content reduce to less than 150 ppm rather less than 10 ppm or even less, which can reduce the cost of protective gas as forming thin-walled parts of nickel-based superalloy such as DZ125L. Practical implications - The appropriate oxygen content in protective atmosphere is helpful for fabricating thin-walled parts of nickel-based superalloy like DZ125L. However, when heavy solid parts of some other material other than DZ125L were fabricated, the oxygen content of less than 150 ppm may be not suitable. Originality/value - The influence of oxidation on the cracks of DZ1251 thin-walled parts in LMDF was investigated in detail, and a DZ125L thin-walled turbine blade with no cracks was fabricated by adjusting the oxygen content in protective atmosphere.