Investigation of Thermal Cycle and Hardness Distribution in the Laser Cladding of AISI H13 Tool Steel Produced by a High Power Direct Diode Laser

Abstract

Laser cladding (LC) of tool steel has significant application in rapid tooling, and surface coating for worn-out components in different industries. During the LC process, several phase transformations influence the microstructural and mechanical properties of the deposited layer. In order to successfully implement the LC process, it is essential to understand the relationship between the thermal cycle (heating and cooling), phase transformations, and the output quantities of the deposited layer. In this study a direct diode laser with a power of up to 8 kW was used to deposit AISI H13 tool steel on mild steel grade A36 substrate to enhance its surface properties. Primarily, an experimentally verified three-dimensional (3-D) heat transfer analysis was developed based on the finite element method to compute temperature history during the cladding and cooling process. Next, the computed thermal cycles were coupled with a semi-empirical thermo-kinetic model to estimate the hardness of deposited layers based on different cooling cycles in a time-temperature-transformation (TTT) diagram. Further, the microstructural details obtained from the cross-sections of the clad were correlated with the estimated thermal cycles and hardness. A good correlation between the modeled and experimental results revealed that the developed model can be used to estimate the microstructural characteristics and mechanical properties of the H13 layer produced by the LC process.