Abstract:

Additive manufacturing (AM) procedures have been used to process parts that require a gradient of properties. The final geometry of the component is divided in layers that allow to tailor the properties of components. Multiple layers are deposit with different alloys to obtain a required set of properties and geometry. Repairing mechanical components involving dimensional rebuilding can take advantage of the attractive characteristics of additive manufacturing. The success of such a procedure is strongly dependent on the deposition technique, selected parameters and the alloys being processed. This study used plasma transferred arc hardfacing (PTA) and aimed at evaluating the effect of processing parameters to produce a “thin wall” structure composed of multilayer single tracks of a Ni-based alloy and NiAl aluminides. Two Ni based alloys were selected, a gamma prime precipitation hardening alloy and solid-solution hardening alloy. The harder and oxidation resistant NiAl aluminides were produced in-situ during the deposition of Ni+Al powder mixtures and constitute the top layers of the structure. Microhardness profiles confirmed the gradient of properties exhibited by the “thin wall” structure produced. Discussion of the effect of the substrate pre-heating temperature, deposition current and velocity on the soundness of the structure considered the crack density, hardness and microstructure formed. Microstructure analysis also included the evaluation of single track multilayer specimens with and without the NiAl aluminides. The efficiency of using Plasma Transferred arc with additive manufacturing procedures on maintenance operation to repair and enhance component performance is assessed.