Ultrasonic surface post-processing of hot isostatic pressed and heat treated superalloy parts manufactured by laser powder bed fusion
Dmytro Lesyk, Silvia Martı́nez, B.N. Mordyuk, Oleksii Pedash, Vitaliy Dzhemelinskyi, Aitzol Lamíkiz
Abstract
Inconel 718 alloy parts were fabricated by the laser powder bed fusion (L-PBF) technique using a multidirectional stripe scanning strategy. Subsequently, the L-PBF-built parts were hot isostatic pressed (HIP), homogenized, and aged. Ultrasonic surface mechanical treatment was applied to modify the surface texture and microstructural layer of the L-PBF-built and heat-treated Inconel 718 alloy parts. Ultrasonic impact treatment (UIT) was implemented using a forcedly rotated multi-pin impact head. The surface texture, roughness, waviness, porosity, microstructure, phase composition, hardness, and residual stresses of the L-PBF-built and thermo-mechanical post-processed specimens were studied and compared. The results revealed that the UIT post-processing leads to work hardening, induces compressive residual stresses, and ∼20% increase in the surface microhardness in the near-surface layer of the heat-treated L-PBF-built 718 alloy parts. The surface roughness and waviness were significantly reduced after UIT, providing a flattened surface microrelief formation.