Removal of Inclusions from Alloy 53 via Heat Flux Manipulation of the Liquid Pool

This project proposes to evaluate the creation of endogenous inclusion defects and the entrainment of exogenous inclusion defects in Alloy 53 during Vacuum Arc Remelting (VAR) processing. Ampere Scientific are the developers of the advanced VAR process monitoring tool, VARmetric™, and have recently provided industrial validation data on superalloy processing.  Additionally, under an NSF grant investigating arc dynamics for reactive metals, Ampere Scientific has developed an active control mechanism for tailoring heat flux during VAR processing of reactive metals. Here we propose to evaluate the efficacy of these technologies to drive VAR operating conditions to favor defect free ingots of Alloy 53. This includes simultaneously creating melting conditions that provide for stable solidification profiles while not creating the turbulent flow necessary to entrain exogenous material in the interior of an ingot. Phase 1 of this project consists of two main goals: 1) To characterize the inclusion content in Alloy 53 under current production methods by determining the size, type, distribution, and locations of inclusions in double vacuum melt Alloy 53 material using the ASTM E45 standard; and 2) to computationally simulate inclusion particle tracking in a VAR furnace operating without and with the application of external magnetic fields. By determining conditions that lead to turbulent flow, and then identifying applied fields effective at stabilizing the turbulent melt pool conditions, we can predict the uniform heat flux required to make defect free Alloy 53 under all conditions. During the Phase I Option, we will relegate these theoretical predictions into practice utilizing the research VAR located at Ampere Scientific. In this case, we will artificially introduce exogenous material (calcium-aluminate) into the interior of an electrode. During melting, the material will be released and will float on top of the melt pool.  Through the application of ARControl™, we will in turn drive the liquid metal flow via arc distribution manipulation to favor turbulent conditions necessary for entraining the material in the interior of the ingot; additionally we will drive the fluid flow to favor non-turbulent conditions that deposit the refractory material at the ingot boundary (along the crucible wall) where it can be removed with standard practices. These experiments serve several purposes: a) to further establish an ingot characterization standard with and without inclusion defects; b) to inform the monitoring and control of turbulent melt conditions that lead to entrainment; and c) to establish the efficacy of control of arc distributions leading to quality control increases. The overall goal of these studies is to prepare for industrial trials at Universal Stainless and Alloy Products during a Phase II effort. The results provided here will provide the baseline for scaling the technology to commercial scale.