On Intertrack Fluctuation of Hardness and Carbides in T15 Steel Laser Cladding Using Thermodynamic Calculation

Intertrack fluctuation of microstructure and mechanical properties is one of the important characteristics for nonuniformity in laser cladding processes. The understanding of the fluctuation helps to improve the wear resistance of deposited materials. In this paper, the phase structure, element distribution, hardness variation and carbides were identified and compared between the cladding zone (CZ) and the heat-affected zone (HAZ) in T15 steel laser cladding. A calculation method was proposed to reveal the physics of the solidification and precipitation behavior of carbides by combining the finite element method (FEM) and thermodynamic calculations. The results showed that the hardness of the intertrack HAZ was higher than the hardness of the CZ due to the high amount and small size of vanadium carbide (VC) particles. The calculation proved that the major strengthening phase was VC precipitate, while tungsten carbide (WC) was not stable in the cooling process and converted to Fe 3 W 3 C. The volume fraction of VC in the HAZ was 14.3%, which was higher than the volume fraction in the CZ, which was only 10.0%. The high temperature was prone to a high volume fraction and many VC precipitates with a small radius in the intertrack HAZ, which qualitatively agreed with the experimental characterization.