Study of LMD of Inconel 718 on Inclined Planes: Influence of Inclination on Width and Height of Deposited Material

Abstract

Laser Metal Deposition (LMD) as a repair technology has been established in recent times. A commonly used material for repairs of turbines are nickel-base alloys, such as Inconel 718 (IN718), which presents good mechanical properties at temperatures up to 650 °C and good corrosive resistance. Inclined or curved surfaces pose a challenge in repairing parts with LMD due to the dependence of height and width of deposited tracks on the local inclination angle. An extensive preparation on path planning is needed to prevent bond defects and to achieve good mechanical properties. The aim of this study is to gain a better understanding of the influence of the local angle between laser beam and component surface on the track geometry. In a first step, single tracks are deposited at various inclinations and process strategies. The track geometries are then evaluated by optical profilometry and metallographic analyses. In a second step, single layers consisting of overlapping tracks are deposited onto different inclined plates, and the welding strategy is varied as follows: a) horizontal overlapping tracks starting from the top going down, b) horizontal overlapping tracks starting from the bottom going up, c) overlapping tracks going up and down. The single layers are analysed metallographically to determine the influence of inclination angle and deposition strategy on the layer height. Furthermore, the influence of inclination on dilution of the base material and on defects such as pores and bonding defects is investigated. By studying the basis of LMD on inclined surfaces, the results presented in this paper help to improve and accelerate path planning for repairs by LMD on freeform surfaces and to design tool paths for the deposition of layers with uniform thickness.