Institute of Fundamental Technological Research

In this paper, the fracture surface topography of additively manufactured Haynes 282 alloy subjected to tensile and high-cycle fatigue loading was investigated. Haynes 282 alloy bars were printed in three different directions relative to the base plate (0°, 45°, and 90°) via Direct Metal Laser Sintering (DMLS) under an argon protective atmosphere. The specimens were subjected to monotonic tensile loading and fatigue testing under load control using full tension and compression cyclic loading (R = −1) in the range of stress amplitude from ±550 MPa to ±800 MPa. The entire surface topography was evaluated by using a 3D non-contact confocal technique and post-failure specimens after a fatigue test performed at three stress amplitudes, ±650 MPa, ±700 MPa and ±750 MPa. Such an attempt was proposed to analyse the fatigue response of AM Haynes 282 in the region near its yield strength. It was found that the printing orientation and the stress amplitude have a strong impact on service life and fracture surface characteristics. Finally, a surface topography parameter involving the mass density of furrows, root-mean-square height, and fractal dimension was successfully combined with the stress amplitude to estimate the fatigue life. The findings offer a novel approach to fatigue life prediction based on post-failure surface analysis, providing valuable insights for industrial applications and forensic engineering.

Nickel alloys,Fatigue,Additive manufacturing,Direct Metal Laser Sintering (DMLS),Fracture,Surface topography

The concept of entire fracture surface investigation is helpful in explaining fatigue phenomena. In this paper, this method has been applied for 18Ni300 maraging steel using a 3D measurement system. Before post-mortem analysis, the specimens produced by laser beam powder bed fusion (LB-PBF) were tested under low-cycle fatigue (LCF) for eight strain amplitudes in the interval 0.3% to 1.0%. The attention was placed on the relationship between the fatigue features, represented by the strain level and the fatigue life as well as the fracture surface topography evaluated in the form of areal, volume and fractal dimension parameters. It was found that fatigue life predictions calculated using the core material volume Vmc, obtained with the entire fracture surface method were within a scatter band with factors of ±1.5. The present results can be useful for the analysis of damaged structural elements exposed to LCF, especially for materials produced by additive manufacturing (AM). The outcomes of this brief note are important for the development of other fractographic methods and validation of fatigue life evaluation procedures.

18Ni300 steel,laser beam powder bed fusion,low-cycle fatigue,surface metrology,entire fracture surface method,fractography,fractal dimension