Cold spray additive manufacturing: A viable strategy to fabricate thick B4C/Al composite coatings for neutron shielding applications

Abstract

This paper presents a design flexible, innovative strategy that can be used for the development, restoration and/or repairing of neutron shielding products in the near future. Cold spray additive manufacturing technique was employed to deposit a 6 mm thick neutron shielding B4C/Al composite coating on a 6061-T6 cylindrical substrate. Microstructure, mechanical behavior and neutron shielding performance of the free standing coating were investigated at different heat treatment conditions in the order: 200, 300, 400 and 500 °C. Microstructure evolutions were characterized using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), laser confocal scanning microscopy (LSM), X-ray diffraction (XRD) techniques, while mechanical properties were investigated via tensile and hardness tests. It was revealed that due to the presence of large amount of inter-splats' defects and intensive cold working, the as-deposited coating exhibited poor strength and fractured in a brittle manner. Moreover, as the heat treatment temperature was increased, the coating gradually recovered the ductility and gained strength due to progressive bonding/healing of inter-splat boundaries through recovery and recrystallization mechanisms. The coating heat-treated at 500 °C displayed maximum ductility (1.4%) and strength (60 MPa) with minimum porosity level of 1.9%. Neutron shielding results showed attenuation of thermal neutrons with increasing sample thickness. Neutron shielding results also displayed a slight improvement in the neutron shielding performance of the sample heat-treated at 500 °C.