Optimization of gas carburizing treatment parameters of low carbon steel using Taguchi and grey relational analysis (TA-GRA).

This work aims to optimize the micro-hardness (H), thickness of the hardened layer (THL), carbon contents (%C) and surface roughness (Ra) of XC10 steel using a gas carburizing thermochemical treatment. The combination of Taguchi and grey relational analysis (TA-GRA) was applied with 9 experiments on the basis of L9 orthogonal design using the following factors: carbon flow rate (0.9%, 1% and 1.2%), temperature (900°, 920° and 940°) and holding time (4 h, 5 h and 6 h). A statistical analysis of the results was carried out on the basis of the S/N ratio and an ANOVA to identify the most significant parameters affecting the experimental responses. A desirability function approach was established to find the optimal factors to maximize H, THL and %C and minimize Ra. The gas carburizing treatment has shown a strong increase in the micro-hardness with about 140%, the thickness of the hardened layer with more than 1400 μm, carbon content 775% and good decrease in the surface roughness (Ra) with 140%.