Processing of Ni Superalloys by Additive Manufacturing Using Plasma Transferred Arc

Abstract

Additive manufacturing (AM) is a process used to build and repair complex shape components or whenever a property gradient is required. In this manufacturing procedure, multiple layers are deposited to fabricate a component. The success of the procedure is strongly dependent on the deposition technique, processing parameters selection and chemical composition of the material being deposited. Also pre-heating and the use of inert atmosphere impact on cracking, wettability and oxidation of the deposited layers. In this study, the potential of plasma transferred arc for additive manufacturing was assessed by the fabrication of “thin walls”. Two Ni superalloys were used, a solid solution hardening and a gamma prime precipitation hardening alloy. The analysis of processing parameters that allowed to process “thin wall”, included pre-heating at 300°C. Results showed that the chemical composition and the using of pre-heating impact on the layers geometry. In both alloys, a fine dendritic solidification structure with epitaxial growth between layers was identified. However, each alloy determined the hardness profile along the cross section. The precipitation hardened alloy is strongly influenced by the deposition thermal cycle of each layer. The solid solution hardened alloy is mainly influenced by dilution of the first layers with the substrate.

Key-words: Additive manufacturing; Plasma transferred arc (PTA); Nickel superalloys