Residual stress relaxation by bending fatigue in induction-hardened gear studied by neutron Bragg edge transmission imaging and X-ray diffraction

•Double induction quenching improves gear fatigue life with surface compressive stress.•Lattice spacing distribution in a fatigued gear can be measured by Bragg edge imaging.•Neutron Bragg edge imaging and XRD suggest residual stress relaxation during fatigue.•Bragg edge imaging and XRD results are complementary due to different gauge volumes.•The obtained insights enhance fatigue models and promote gear production development.