Optimisation of multiple quality characteristics of hardfacing using grey-based Taguchi method

Hard-particle metal matrix composites (MMC) represent an efficient way of increasing the lifetime of machinery equipment which is exposed to severe wear conditions. The abrasive wear resistance of these materials, usually designed by reinforcement with tungsten carbides, is highly dependent on the MMC's microstructure. Plasma transferred arc (PTA) is a commonly used and efficient welding method for hardfacing deposition. Dissolution of carbide markedly influences the microstructure parameters, decreasing the carbide volume fraction as well as the mean carbide diameter, whereas matrix hardness increases with increasing carbide dissolution. However, optimisation of the multiple, process determining quality characteristics is a key factor for successful application in industrial practice. In this paper, the grey relational Taguchi method was used for the optimisation of PTA-processing in hardfacing of WC/W2C-reinforced Ni-based MMC, considering multiple quality characteristics of the microstructure parameters relevant to abrasion resistance. An L-8 orthogonal array with three control factors (welding current, welding speed and oscillating speed) was used to study linear effects and interactions on signal-to-noise ratios of the various quality responses (carbide volume fraction, equivalent diameter, matrix hardness). Based on this study, optimised processing conditions of the hard-particle MMC fabrication were defined. (C) 2011 Elsevier Ltd. All rights reserved.