Laser cladding strategies for producing WC reinforced NiCr coatings inside twin barrels

- Laser cladding of WC reinforced NiCr alloy inside twin barrels was studied.
- Energy input must be controlled in order to prevent clustering of carbide particles.
- Large crushed powders produce best results instead of small and spherical ones.
- A buffer layer and preheating are needed for producing crack-free coatings.

Thick and hard coatings are widely applied in a substantial number of heavy-duty industrial applications to improve wear and corrosion resistance. The techniques that allow producing depositions of metallic, ceramic or metallic-ceramic mixtures in zones with difficult access, like inner walls of a cylinder, are quite limited. Methods like spin casting, for instance, are successfully applied in parts with cylindrical symmetry. Nevertheless, when parts with more complex geometries have to be coated, new solutions must be applied. The use of laser cladding as a possible alternative for these applications is studied in the present work. Coatings of a NiCr matrix reinforced with hard tungsten carbide particles were produced in internal walls. Carbides with different shape and size were employed in order to find the most suitable candidate for producing defect free coatings with maximum thickness. In order to achieve this goal, the effect of different processing parameters was investigated. The use of preheating and a soft buffer layer were also considered for minimizing the thermal stresses produced during the rapid cooling of the coating, from the melting point to the solid state.