Fatigue Performances of Additively Manufactured γ‐TiAl and IN939 Alloys in As‐Built and Laser Shock–Peened Conditions

ABSTRACT The surface condition of additively manufactured (AM) parts strongly influences fatigue performance. Laser shock peening (LSP) is an effective surface enhancement method that improves the quality of AM metals by introducing compressive residual stresses (CRSs). In this study, two different metallic alloys, γ‐TiAl and IN939, were manufactured using powder bed fusion (PBF) techniques. The γ‐TiAl alloy was produced via electron beam melting (PBF‐EB), while IN939 was fabricated through laser powder bed fusion (PBF‐LB). After fabrication, all specimens were subjected to LSP and then tested under four‐point bending fatigue conditions. The results were compared between the as‐built and LSP‐treated conditions. For the PBF‐EB γ‐TiAl alloy, a fatigue limit was determined based on the 2 × 10 6 cycle run‐out criterion, and LSP led to a 50.1% increase in the fatigue limit. For the PBF‐LB IN939 alloy, because none of the as‐built samples reached the run‐out cycle threshold, fatigue life comparisons were made at selected normalized stress levels. The LSP‐treated specimens showed fatigue life improvements by factors of 1.87 and 3.72 at stress levels of 0.74 and 0.87, respectively. Scanning electron microscopy (SEM) was used to evaluate the fracture surfaces, and the influence of LSP on fatigue behavior was discussed for both alloys.