Optimization of processing parameters, physical and mechanical properties of SiC – CNF composites using Taguchi approach

Abstract

Abstract Silicon carbide (SiC) based composite with the low specific weight, the high specific strength over a large temperature range, and their great damage tolerance compared to their monolithic counterpart make them extremely useful as a high temperature load bearing material for many advanced applications. However, the reliability of these highly tough fibre containing composites pose a problem in actual use unless consistent material properties are maintained by adopting optimized processing parameters. In this study an attempts have been made to develop carbon nanofibers (CNF) dispersed thin SiC tubes used in applications like nuclear industries, power industry, semiconductor industry, chemical and paper industries etc. The material properties of the composite tubes were optimized through design of experiments to optimize the parameters like sintering temperature, heating rate, holding time and at different CNF compositions by using Taguchi experimental design method with an L9 (3^4) orthogonal array. Further, experiments were designed at the optimized processing conditions to evaluate the effect of particle size of SiC and CNF loading on properties of SiC-CNF composites by choosing an L9 (3^3) orthogonal array of design. The experimental results i.e. performance parameters were analysed by Taguchi optimization method and microstructure analysis. The effect of variables on the properties of the composites were studied from the signal to noise ratio (S/N), analysis of variance (ANOVA), and interaction plots. Processing at optimized conditions through design of experiments resulted in obtaining best properties when the values mentioned in parenthesis for the respective processing parameters like sintering temperature (2150°C), heating rate (8°C/min) and holding time (1hr) were maintained. SiC based composite with 1wt% CNF loading was identified to be the best homogeneous composite with superior properties at optimized design parameters. Thin composite tubes with wall thickness around 1mm with superior properties having density - 3.21g/cc, hardness - 26.5 GPa, fracture toughness - 5.12 MPam1/2respectively were than fabricated for further use in nuclear applications.