Finite element analysis of thermal cycle in laser cladding for railway repair

Abstract

Material degradation in the forms of wear and rolling contact fatigue is one of main hindrances in the development of today's expeditious heavy-haul railway systems. Laser cladding is proposed as a promising repair technique for damaged rail tracks so as to mitigate the material degradation rates and prolong the component service life. This paper reports the influence of laser cladding directions on thermal cycle and the corresponding mircostructures and service performance of laser cladded premium hypereutectoid rails. For two separate cladding directions, thermal information of pre-, during and post-laser treatment on three dimensional 68 kg rail models was simulated via ANSYS platform. Furthermore, microstructural characteristics of the actual rails under the analogous processing conditions were assessed via optical microscopy. Potential mechanical and tribological properties were characterized by Vickers indentation. The unified correlations between the measured properties and observed microstructural features were acquired. The reasons for the formation of martensite renowned for great cracking tendency at certain regions in HAZ were unveiled, thus future prevention of forming martensite can be achieved.