Cold-spray repair of CuCrZr crystallizers: Effect of substrate pretreatment

Abstract

Cold spraying is a promising technique for repairing damaged CuCrZr crystallizers, and the interface between the repair coating and the substrate plays a critical role in determining the heat transfer efficiency of the repaired crystallizers. In this study, two coating/substrate interfaces were prepared through polishing and grit-blasting the CuCrZr substrate surface. Effect of substrate pretreatment on microstructure and performance of the CuCrZr coating was studied using electron backscatter diffraction, adhesive shear strength and thermal conduction tests. Results show that the surface preparation method does not affect the microstructure and hardness of the CuCrZr coating, but the coating sprayed on the grit-blasted substrate has a lower shear adhesive strength and heat conductivity than the coating sprayed on the polished substrate. This difference is attributed to the formation of a work hardening zone during the grit-blasting process. After releasing this work hardening by annealing at 500°C, the difference in heat conductivity then disappears, but the average shear adhesive strength of the annealed coating on the polished substrate is still higher than that on the grit-blasted substrate. Therefore, polishing the substrate could serve as a more viable option for the cold spray repair of CuCrZr crystallizers.