Post-Process Superfinishing of Additively Manufactured Components for Next-Gen Space Application

N. Michaud, A. Diaz
REM Surface Engineering,
United States

Keywords: additive manufacturing, space applications, post-process superfinishing


Additive Manufacturing (AM) is revolutionizing many industries, including the aerospace and space industries. AM allows for rapid printing, greatly reduced lead times, and complex designs/features not possible via traditional manufacturing. Additionally, AM has facilitated a range of new alloys and superalloys with extremely high mechanical and performance characteristics, representing great potential for space components such as firing chambers and fuel nozzles with complex internal cooling channels. Unfortunately, as-printed AM components also carry many inherent challenges and issues that can hinder performance or even lead to critical component failure, hindering access to the benefits described above. These defects include partially sintered/unsintered powders, surface waviness/roughness, and surface and near-surface porosity as artifacts of the printing process. REM Surface Engineering, founded in 1965, has been a leading provider of isotropic superfinishing services in traditional industries for decades. We have recently adapted our existing technologies and developed new technologies to create a superfinishing process capable of remediating all surface and near surface defects on AM components. In a process which combines unique proprietary chemical polishing and chemical/mechanical polishing, we are able to remediate all surface defects, as well as near surface defects, as well as polish internal channels/non-line-of-sight surfaces (something which traditional processes such as machining cannot accomplish). Furthermore, the process has been proven to increase fatigue life and performance over as-printed parts. Since being awarded a our first Phase I NASA SBIR contract in 2018, REM has received over $3.1 million in federal funding to adapt this process for NASA Marshall and NASA JPL’s unique needs, including alloys printed in Inconel 625, Inconel 718, NASA HR-1, GrCOP-42, GrCOP-84, JBK-75, and is currently in development for the U.S. Air Force in alloys Al-6061-RAM2, Scalmalloy, A7050, Ti-6Al-4V, and F357 and develop guidelines for the production of high-use IN-718 AM components. Components having been processed via REM’s technology (combustion chamber + fuel nozzle) have recently undergone hot-fire testing, and have survived 23 three hot-fire tests. Implementation projects are underway for ongoing research and processing of full-scale propulsion components for NASA as well as commercial industry customers. This presentation will focus on detailed examples of the implementation of the current technology and its resulting performance benefits, as well as potential examples of component applications possible for future research. Examples of existing and potential space component implementation to be reviewed include: nozzles; combustion chambers; barrels; thruster chamber assemblies; cooling channels; fuel injectors; impellers & blisks; structural components including brackets, lattices, and honeycombs; and power transmission components. Some of the proven benefits to be reviewed include: increased high cycle fatigue life; uniform hotwall thickness reduction for cooling; uniform surface roughness reduction for cleanliness/coating and overlap adhesion; cooling channel FOD removal; cooling channel/fuel injector roughness reduction for reduced flow resistance/pressure; controllable cooling channel/fuel injector diameter increase; removal of detrimental oxide layers due to HIP; elimination of granular roughness; improved contact fatigue life for power transfer components; improved flow dynamics for turbomachinery; uniform metal removal from highly complex component shapes including iterative/bionic designs, lattices, and honeycombs (allowing for ultra-thin wall generation.)