Heat Treatment of Alloy 718 Made by Additive Manufacturing for Oil and Gas Applications

Abstract

The ability to consolidate parts in complex assemblies using metal additive manufacturing offers transformational product development opportunities. Specifically, the high value capability for printing complex shapes and channels using metal laser powder bed fusion is a key enabler to realizing this vision. A thorough understanding of microstructure and defects specific to industry standard heat treatments and thermal processing is essential for fielding additively manufactured parts. The goal of this work was to evaluate oil and gas application specific heat treatments on Alloy 718 built using laser powder bed fusion. In the present study, the influence of heat treatment steps relevant to the use of Alloy 718 for components under American Petroleum Institute Specification 6A have been investigated. Multiple heat treatment conditions as well as hot isostatic pressing were studied and compared to the as-built material using a combination of thermodynamic simulations and metallurgical characterization. The overall conclusion of this study is that none of the studied heat treatment approaches is appropriate for American Petroleum Institute Specification 6A and that specific thermal post-processing routes compliant to the specification need to be considered.