Session: 18-05 Additive Manufacturing - Design and Components for Gas Turbine Engines

Paper Number: 83474

83474 - Characterization of Properties of Laser Powder Bed Fusion 3D-Printed Inconel 718 for Centrifugal Turbomachinery Applications 

The ever-present demand for higher efficiency and lower cost turbomachinery for power and propulsion applications will require the incorporation of innovative and cost-effective manufacturing processes. In particular, the aerodynamic components of centrifugal turbomachinery (e.g., compressor impellers and turbine wheels) hold significant potential for efficiency gains and cost reduction that cannot be simultaneously achieved by traditional manufacturing methods like CNC machining. The rise of additive manufacturing (AM), or 3D printing, methods presents great opportunity to tap into the aforementioned potential. As a result of recent process and material technology advances, one type of 3D printing method, laser powder bed fusion (LPBF), has been identified as capable of providing the design flexibility and geometric precision necessary to achieve both higher performance turbomachinery designs and reduce associated manufacturing costs.

To date, there is a serious lack of information on the metallurgical and mechanical properties of common alloys available for 3D printing of mechanical components. For example, data such as the modulus of elasticity or 0.2% yield stress as functions of temperature and chemical composition are not publicly disseminated for most alloys currently available for use in AM. The extreme stress, high temperature, and corrosive/reactive environments that often characterize turbomachinery rotating component operation can represent serious reliability and safety risks that can only be managed by knowledge of these indispensable properties.

This paper presents the results of a comprehensive effort to characterize the properties of Inconel 718 manufactured by a modified version of the LPBF method, and subsequently subjected to hot isostatic press (HIP) and heat treatment according to standards F3055-14a and AMS 5663, respectively. The authors have found Inconel 718 to be ideally suited for 3D printing low cost, high speed centrifugal impellers and turbine wheels that incorporate geometries like shrouds and internal cooling passages. Heretofore, these components were too costly to manufacture for certain applications like blowers for solid oxide fuel cell anode exhaust recycling or compressors for low-cost microturbines. The paper includes: 1) Results of basic chemical and metallographic analyses of multiple samples; 2) Plots of tensile properties, namely 0.2% yield stress, ultimate stress, modulus of elasticity, and elongation to failure based on 108 samples, all as a function of both temperature and print orientation; 3) Creep data for different temperatures, including Larson-Miller parameter, based on 21 samples, and 4) High cycle fatigue data at different temperatures based on 21 samples. The results of the study are compared to appropriate standards and/or data for forged, cast, and other AM Inconel 718 wherever possible. A key conclusion of this study is that due to an incomplete recrystallization of the material, the LPBF method for 3D printing of Inconel 718 yields a material with mechanical properties (e.g. yield stress, creep tolerance) measurably lower than those broadly available for its forged counterpart, but higher than those of cast material. As such, the authors conclude that LPFB 3D-printed Inconel 718 is more than adequate for high stress centrifugal blower and compressor applications, as long as the operating temperatures are well below those of the material aging temperatures.

Presenting Author: Hannah Lea Mohawk Innovative Technology, Inc.

Presenting Author Biography: Hannah Lea is a mechanical engineer at Mohawk Innovative Technology, Inc. (MiTi) in charge of turbomachinery design and finite element analysis and simulation. Ms. Lea received her B.S. in mechanical engineering from Binghamton University in 2020. During her tenure at MiTi, she has contributed to the design of 3D-printed impellers and other blower components, performed thermal management analysis and general mechanical design for a gas turbine engine (microturbine), and has participated in experimental campaigns and data processing for several power and energy projects. In her free time, Ms. Lea is an avid reader, lover of music, and dog mom.

Authors:

Hannah Lea Mohawk Innovative Technology, Inc.
Rochelle Wooding Mohawk Innovative Technology, Inc.
John Rotella USAF Research Laboratory
Jose Luis Cordova Mohawk Innovative Technology, Inc.
Sam Kuhr Air Force Research Lab, Materials and Manufacturing Directorate, AFRL/RXCM, Wright Patterson AFB