Optimization of Porosity Response in Electroless Ni-YSZ Co-Deposition

Abstract

Background/Objectives: The paper discusses on the porosity content optimization by varying electroless nickel codeposition process parameters in the Ni-YSZ coating. Methods/Statistical Analysis: The Ni-YSZ co-deposition was produced by electroless nickel process co-deposited with 8mol% Yttria Stabilized Zirconia (YSZ) powder on alumina substrate. ElectrolessNickel (EN) process parameters investigated in the study were bath loading ranges between 225- 150 ml, bath temperature ranges 84-94oC, stirring speed between 250-500 rpm and pore formers namely graphite, activated carbon and starch. Design of Experiment (DoE) Taguchi L9 method was used and analyzed by statistical tool analysis of variance (ANOVA) in Minitab software. Findings: The rank of parameters affecting the porosity response is the bath loading, poreformer, stirring speed and lastly the bath temperature. The best optimum condition at nominal setting for porosity response is bath loading at 225 ml, bath temperature at 890C and stirring speed at 375 rpm. Graphite pore former gives the most reliable porosity formation compared to activated carbon and starch. This was supported by the Scanning Electron Microscope (SEM) micrographs. Applications/Improvements: In general, standard bath temperature of 890C and moderate stirring speed at 375 rpm that gives better porosity content. Coating surface was analyzed using SEM coupled with Energy Dispersive X-ray (EDX) which shows the presence of nickel and YSZ elements.