Finite element investigation of residual stresses during laser powder deposition process as an innovative technique to repair worn rails

Abstract

In recent years, a great deal of effort has been made to use laser powder deposition (LPD) as a novel way of repairing damaged metal components. Minimizing the residual stress in the LPD process to prevent premature failure and delamination is very important, so the proper deposition material and technique must be used. This paper studies the use of the LPD process to repair a standard U.S. light rail by building up multiple deposition layers onto the worn railhead. The investigation of the rail repair process was performed through the systematic finite element modeling of the multi-layer LPD process using the element birth-and-kill technique. In this technique, the effects of the type of deposition material and the preheating temperature on the magnitude and distribution of the residual stresses were studied. The candidate deposition steels included 304L stainless steel, 410L stainless steel, Stellite 6, and Stellite 21, each one of which was explored separately. To analyze the effect of preheating, various temperatures, that is, 25°C, 400°C, 600°C, 800°C, and 900°C, were set as the initial temperatures of the railhead. Ultimately, it was shown that preheating has a significant effect in minimizing the residual stresses. It was found that each increase in the preheating temperature resulted in an overall decrease of the residual stresses by 25%–30%. In addition, Stellite 21 was identified as the most promising deposition steel in terms of giving the least risk of failure and delamination.