Procedures for interface residual stress determination using neutron diffraction: Mo-coated steel gear wheel

Residual stresses were determined in steel gear wheels coated with molybdenum using neutron diffraction. A systematic procedure was developed to assess them in both the molybdenum coating and in the steel substrate. A detailed description of the problems associated with measurements of this type is given, together with a procedure aimed at rationalising their solution.Precise sample positioning was developed using a new experimental method and advanced metrology equipment allowing off-line sample alignment and mounting. This reliably replaces the inefficient use of entrance scans, usually adopted in residual stress analysis by neutron diffraction. Corrections were applied to overcome the presence of pseudo-strains and data reduction was performed to coherently interpret the results, including the determination of the centre-of-mass of the diffracting volume. The full three-dimensional stress profile was determined in the coating and the substrate. The data analysis methodology is fully described and recommendations are given for this kind of measurement.