Heat-Assisted Additive Manufacturing and Post-Heat Treatment of Inconel Supper Alloy: Investigating the Microstructure and Mechanical Properties

Abstract

Recently, additive manufacturing (AM) has gained attention in the global manufacturing industry. The advantages are derived from the fact that it is a powder-based manufacturing process. The AM process enables the fabrication of complex parts that can be manufactured at a lower cost. This approach allows on-demand production, minimal structural limitations, and custom design. Many industries are concerned about the reliability and durability of AM metallic parts. The properties of the materials are not entirely known, and imperfections resulting from the production process are frequently detected, which lowers the performance of the material. Consequently, many studies have been conducted on the microstructures and mechanical properties of materials produced by AM. With recent advances in AM over the past decade and the introduction of high lasers and higher-quality raw materials, AM can produce functioning components with high mechanical performance. The manufacturing and post-fabrication processing conditions, in addition to post-heat treatments, strongly influence the microstructure and mechanical characteristics of additively manufactured components. Metal components are affected by the manufacturing orientation, such as the laser power, laser scanning speed, and powder layer thickness. Anisotropic mechanical behaviors, such as tensile strength and stiffness in additively manufactured components, are caused by the directed fabrication method and thermal history, which provide a microstructure different from that anticipated in traditional production. In addition, additively manufactured components are unpredictable because of imperfections generated by the unmelted powder or entrapped gases during manufacturing. This dissertation investigates the influence of various processing factors on the microstructure and mechanical behavior of additively manufactured components. In addition, a better understanding of how modified heat treatment and building process parameters affect the mechanical behavior and microstructure and how to account for them when designing products may lead to more durable and reliable components. The layer-by-layer manufacturing approach intrinsic to AM permits a heat input. Therefore, the thermal gradient and solidification rates vary throughout the process, resulting in changing solidification conditions and thus various solidification microstructures. The processing parameters used during fabrication and post-processing significantly affect the microstructure and mechanical performance of the additively manufactured parts. The first objective of this investigation was to study the influence of different processing variables using heat-assisted AM on the microstructure and mechanical performance of IN718 additively manufactured components. The second objective of this study was to optimize the post-heat treatments for IN 718 materials fabricated by AM. The third objective is to model the combined effect of heat-assisted AM and post-heat treatments on the precipitates δ, γ', and γ'' using Neural Network.