Inferior fatigue resistance of additively-manufactured Ni-based superalloy 718 and its dominating factor
Sungcheol Park, Yuya Tanaka, Saburo Okazaki, Yusuke Funakoshi, Hideto Kawashima, Hisao Matsunaga
Abstract
Push-pull and torsional fatigue tests were conducted using additively-manufactured, Ni-based superalloy 718 samples with various defects and different microstructures, aiming to comprehensively examine fatigue limit determining factors such as detrimental defects and microstructural features. Test results revealed that the fatigue limit in each loading condition was governed by a shear-mode, crack-growth threshold, exhibiting a crack-size dependence similar to that of the wrought alloy. The additively-manufactured materials displayed a substantially reduced crack threshold as compared to wrought ones, potentially attributed to a high volume of low twist angles between neighboring crack-planes.