Session: 02-02-02: Characterization of Additively Manufactured Metal Parts

Paper Number: 71975

Start Time: Wednesday, 01:00 PM

71975 - The High Cycle Fatigue Behavior of Surface Treated Electron Beam Melted Titanium Ti6Al4V 

With the growth of Additive Manufacturing (AM) or 3D printing in the aerospace and medical sectors, the need for long lasting metal components in high-stress applications is becoming increasingly crucial. When compared to conventionally produced metal parts, one of the biggest limitations is the low fatigue life of AM components due to a variety of factors including build orientation, surface roughness, and internal defects. To address the low fatigue behavior of metal AM components, there has recently been an increase in interest in performing post processing treatments on additive manufactured components. However, the majority of research has concentrated on performing conventional surface treatments such as machining or polishing, with limited attention on tool-less surface treatments. With AM’s unique ability to produce unique and complex shapes, the ability to perform conventional surface treatments on printed parts becomes difficult and limited. The effects of tool-less post processing techniques on fatigue life titanium Ti6Al4V specimens have been explored in this study with specimens undergoing hot isostatic pressing (HIP), in addition to a surface treatment process such as cavitation peen, shot peen, laser peen or cavitation abrasive surface finishing. Uniaxial high cycle fatigue testing has been performed on untreated, HIP, and HIP + surface treated cylindrical specimens manufactured using electron beam melting (EBM). The location of crack initiation and propagation have been determined through the use of optical and scanning electron microscopes (SEM). Additionally, the effects and presence of internal porosity are evaluated using micro-Computer Tomography (µCT). The HIP process alone does not show an increase in fatigue life, however, did assist in reducing the scatter in stress-life data. The cavitation peen process did not generate a notable increase in fatigue life and performed similarly to the untreated specimens. However, the shot peen and laser peen titanium specimens exhibited the greatest increase in fatigue life when compared to the untreated EBM specimens. To further understand the relationship between surface roughness, surface treatments, and fatigue life, the Arola-Ramulu (AR) Model was used. Utilizing the AR model, surface characteristics of the untreated and treated EBM components are evaluated at specific locations as areas of high stress concentration and correlated to fatigue life. Through developing a better understanding of the effects of surface characteristics on fatigue life, improved surface treatments can be recommended for EBM components. Additionally, these finding can further promote the use of metal AM components for high loading applications in the medical, aerospace, and automotive industries.

Presenting Author: Melody Mojib University of Washington

Authors:

Melody Mojib University of Washington
Hitoshi Soyama Tohoku University
Daniel Sanders University of Washington
Dwayne Arola University of Washington
M. Ramulu University of Washington