MATEC Web Conf.
Volume 165, 201812th International Fatigue Congress (FATIGUE 2018)
|Number of page(s)||6|
|Section||Residual Stresses in Fatigue|
|Published online||25 May 2018|
Influence of surface residual stresses on the fatigue life and crack propagation behavior of turned Inconel 718 super-alloy
Ecole de Technologie Supérieure, Mechanical Engineering Department, 1100 Rue Notre-Dame Ouest, Montréal, H3C 1K3, Québec, Canada
2 Pratt & Whitney Canada, 1000 Rue Marie-Victorin, Longueuil, J4G 1A1, Québec, Canada
3 Ecole Polytechnique de Montréal, Mechanical Engineering Department, 2900 Boulevard Edouard-Montpetit, Montréal, H3T 1J4, Québec, Canada
* Corresponding author: email@example.com
The effects of surface roughness parameters and residual stresses induced by finish turning on fatigue life and crack propagation behavior of Inconel 718 super-alloy are investigated. A criterion serving as a good indicator of surface quality is also discovered. This is carried out for some specific turning conditions in order to control surface characteristics including surface roughness and the bi-axial state of surface residual stresses and to investigate the effects of these characteristics on fatigue behavior. Rotating bending fatigue (RBF) tests are performed on the machined specimens at room temperature. Characterization techniques including X-ray diffraction (XRD), laser confocal microscopy, and opto-digital microscopy are used to investigate surface residual stresses in axial (ARS) and hoop (HRS) directions, surface roughness, and secondary fatigue cracks, respectively. The huge dispersion in fatigue life of smooth turned Inconel 718 with very low arithmetic average roughness (Ra) values indicates that surface finishing is not the only reliable criterion for quality control of machined components. Multivariate statistical analyses show that axial surface residual stress is the most important surface characteristic affecting the fatigue life of machined Inconel 718 for the conditions tested. Changing ARS from compressive to tensile increases the number of secondary cracks and also decreases the fatigue life of turned specimens.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).
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