Structure and properties of electrodeposited Ni-Co-YZA composite coatings

The aim is to develop an economical composite coating with high thermal stability. Ni-Co alloys are found to possess better thermal, physical and mechanical properties compared to Ni. Also, oxide particles as distributed phase can impart better thermal stability. Hence, particulates of composite Yttria stabilised zirconia, a commonly used high temperature material and alumina (YZA) were reinforced in various Ni-Co alloy matrices through electrodeposition. The influence of YZA on the microhardness, tribology and corrosion behaviour of Ni-Co alloys with Co contents of 0 wt.%, 17 wt.%, 38 wt.% and 85 wt.% was evaluated. Optical and Scanning Electron Microscopy (SEM) confirmed the presence of YZA particles and Energy Dispersive X-ray Analysis (EDX) revealed the composition. Tribology testing showed that composite containing 38 wt.% Co displayed better wear resistance. It was found from the immersion corrosion studies that Ni-17Co-YZA coating displayed improved corrosion resistance. Thermal stability studies showed that Ni-85Co-YZA coating retained its microhardness at temperatures of 600oC. Thus, these coatings can be tailored for various applications by varying the cobalt content