Effects of Printing Layer Orientation on the High-Frequency Bending-Fatigue Life and Tensile Strength of Additively Manufactured 17-4 PH Stainless Steel

Hamed Ghadimi, Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.
Arash P. Jirandehi, Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.
Saber Nemati, Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.
Huan Ding, Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.
Abdelrahman Garbie, Department of Mechanical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70503, USA.
Jonathan Raush, Department of Mechanical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70503, USA.
Congyuan Zeng, Department of Mechanical Engineering, Southern University, Baton Rouge, LA 70807, USA.
Shengmin Guo, Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.

Abstract

In this paper, small blocks of 17-4 PH stainless steel were manufactured via extrusion-based bound powder extrusion (BPE)/atomic diffusion additive manufacturing (ADAM) technology in two different orientations. Ultrasonic bending-fatigue and uniaxial tensile tests were carried out on the test specimens prepared from the AM blocks. Specifically, a recently-introduced small-size specimen design is employed to carry out time-efficient fatigue tests. Based on the results of the testing, the stress-life (S-N) curves were created in the very high-cycle fatigue (VHCF) regime. The effects of the printing orientation on the fatigue life and tensile strength were discussed, supported by fractography taken from the specimens' fracture surfaces. The findings of the tensile test and the fatigue test revealed that vertically-oriented test specimens had lower ductility and a shorter fatigue life than their horizontally-oriented counterparts. The resulting S-N curves were also compared against existing data in the open literature. It is concluded that the large-sized pores (which originated from the extrusion process) along the track boundaries strongly affect the fatigue life and elongation of the AM parts.