Optimization of spark plasma sintering parameters of inconel 738LC alloy using response surface methodology (RSM)

Abstract

The quality and properties of a material can be improved by the choice of processing technique adopted. This study investigates the influence of process parameters of spark plasma sintering (SPS) method on the densification and microhardness properties of IN738LC superalloy. In order to reduce the numbers of experiments and eliminate trial by error approach, design of experiment (DOE) approach was adopted. This involved the use of response surface methodology and central composite design (CCD) with temperature and pressure as the SPS experimental variables. Analysis of the variance (ANOVA) was studied to validate the developed model, coupled with understanding the influence of individual variable and their combined interaction on the output (responses). In this case, the responses were the density and the hardness properties. The data obtained from the numerically predicted values and the physical experiment was statistically examined to obtain a predictive model which harmonizes the density and the hardness as a function of the independent operation parameters. Empirical models were developed for the responses and fifteen solution runs was processed to establish whose response desirability is closest to 1. It was observed that SPS processing temperature (variable) have a major effect on the responses and the most desired temperature is 1200 °C at 50 MPa pressure. Under this condition, the hardness is 362.028 HV and the corresponding percentage relative density id 98.457% (7.772 g/cm3). The theoretical density is given as 7.894 g/cm3. Keywords: Optimization, IN738LC alloy, Density, Hardness, Temperature, Pressure