Use of misorientation values to further understand deformation in rail steels

Abstract

The high contact stresses between a railway wheel and rail result in local plastic deformation in both the rail and wheel steel. Optical metallography and hardness testing have traditionally been used to quantify the extent of deformation present; however, these methods only give limited information about the deformation mechanism and the role of microstructure. In this study, electron backscattered diffraction has been used to assess the depth and degree of deformation using the kernel average misorientation function; where the crystallographic misorientation between and within pearlite colonies has been quantified using a local average misorientation function. This technique gives invaluable crystallographic information about the deformed microstructure to aid understanding of the deformation mechanism. The application of the kernel average misorientation function has been modelled for idealised rail microstructures, including after the simulation of deformation via shear, in order to understand how the average kernel average misorientation values are developed under the high levels of deformation seen in rail steels.