Additively manufactured GRCop-42 copper-alloy combustion chamber failure analysis: The role of build interruptions

Abstract

During hot-fire testing, an additively manufactured (AM) Laser Powder Bed Fusion (L-PBF) GRCop-42 rocket engine combustion chamber failed, providing a case study for proper AM process rigor, particularly for builds with interruptions. This paper describes test day events, chamber manufacturing and post processing, and material evaluations used for understanding failure root cause. The chamber failure occurred at a build interruption location (witness line). Metallographic analysis of the failed chamber and adjacent chambers from the same build revealed excessive porosity, three orders of magnitude higher than typical GRCop-42, concentrated near the witness lines. This porosity reduced tensile strength and elongation, contributing to the failure. In contrast, test bars emulating build interruptions demonstrated no reduction in strength, elongation, or fatigue life, confirming that properly executed restart procedures do not inherently weaken GRCop-42 components. The failure likely resulted from a cascade of events, highlighting the need for stringent process controls in AM.