Abstract
Cold spray technology is commonly used to repair metallic components with limited temperature influence on the original component. However, for many commercial alloys, such as Al6061, it is still challenging to achieve dense deposits by using low-priced nitrogen gas. The objective of this work was to investigate the effect of secondary peening with zirconia (ZrO2) ceramic beads on the microstructure and mechanical properties of the Al6061 cold spray coatings. Al6061 spherical powder with an average size of 20 mu m coupled with zirconia beads of similar to 210 mu m were deposited onto Al6061-T6 substrates using N-2 as the carrier gas. The microstructure and mechanical properties of coatings were compared with coatings produced using He and N-2 process gases. Microstructural characterization was performed using optical and scanning electron microscopy. Coatings produced with He process gas resulted in lowest porosity and with better mechanical properties compared to the coatings produced using N-2 and N-2 along with ZrO2. The use of ZrO2 along with N-2 process gas resulted in similar to 15% increase in microhardness, similar to 680% increase in adhesion strength, similar to 28% reduction in porosity, and similar to 34% increase in tensile strengths in the coatings when compared with the coatings produced using N-2 process gas only. However, both coatings produced using N-2 and N-2 coupled with ZrO2 exhibited brittle behavior with no appreciable ductility. Even with this limitation, using ZrO2 as a secondary peening media could provide a cheaper alternative to using He gas for certain cold spray applications where a higher hardness and good adhesion strengths are needed.
NSTL
Elsevier