Kinetics of the Dissolution of Tungsten Carbides Induced by Advanced GMAW Hardfacing Processes to Produce MMC Coatings

Abstract GMAW hardfacing with consumables containing tungsten carbides is limited by the dissolution of the carbide particles in the droplet and subsequently in the weld pool. This study investigates the dissolution behavior of unmodified, commercially used eutectoid WC/W 2 C carbides (WSC) and carburized variants (cWSC) featuring a stabilizing WC surface layer under an energy-reduced, controlled short-circuit GMAW hardfacing process. Thermal exposure is considered as two consecutive stages involving dissolution in the molten droplet and diffusion-dominated dissolution during weld-pool residence. Transient electrical process data and weld-pool surface temperature measurements are used to determine the specific droplet enthalpy and the relevant temperature–time regimes. An analytical model based on the shrinking-core concept is developed to quantify carbide dissolution as a function of particle size and cooling time and is validated experimentally by statistical particle-size analysis and particle-counting methods. The results reveal a pronounced size dependence of dissolution, with particles smaller than approximately 80 µm undergoing extensive degradation largely independent of heat input. Carburized carbides exhibit significantly reduced dissolution compared to conventional eutectoid carbides, retaining an intact WC surface layer throughout processing. Furthermore, dissolution is markedly enhanced in iron-based melts compared to iron-nickel systems, indicating that Fe-Ni matrices in combination with carburized carbides are preferable for minimizing carbide degradation in GMAW hardfacing applications.