Investigating Homogenization Kinetics in IN718 Alloy: A Comprehensive Strategy Involving Si-Enriched Scrap Utilization and Optimization of Two-Stage Heat Treatment.

The investigation of IN718 alloy for aerospace and oil and gas industries focuses on cost-effective component design, specifically for turbines. Manufacturers for IN718 can achieve cost-effectiveness by acquiring recycled materials in the form of scrap. This recycling approach not only addresses economic considerations but also aligns with environmental goals such as reducing greenhouse gas emissions. In the production process, utilizing scrap with higher Si content could reduce costs. However, precise microstructure control is necessary to mitigate microsegregation and secondary phases that impact final product properties. Homogenization treatment minimizes microsegregation, making the alloy suitable for further processing. In this study, as-cast IN718 alloy with 0.2 wt pct Si is homogenized at 1100 °C, 1150 °C, and 1175 °C for 12, 36, 60, and 96 hours. Solute redistribution in as-cast and heat-treated alloys was assessed using SEM-EDS-based area analysis by scanning approximately 2000 uniformly distributed points. The SEM-EDS data analysis yielded concentration profiles for each element in the investigated alloys. Homogenization was determined based on delta values (the difference between maximum and minimum solute concentration) as a function of temperature and time. Homogenization at 1175 °C for 96 hours showed the lowest delta values and is recommended as the suitable heat treatment. Additionally, a diffusion-based homogenization model predicts homogenization extent with respect to temperature and time. The model suggests a two-stage heat treatment: 1150 °C for 25 hours and holding at 1200 °C for 30 hours. [ABSTRACT FROM AUTHOR]