Investigation of Titanium Effects on the Behavior and Corrosion Mechanism of Hadfield Steel By Using Electrochemical Tests and Electron Microscopy Studies

In this study, effect of titanium on the behavior and corrosion mechanism of Hadfield steel by using electrochemical tests and electron microscopy studies was investigated. For this purpose, initially 3 casting samples were prepared from Hadfield steel in coreless induction furnace (without Ti addition, and with 0.5% and 1% Ti additions). Then austenitising heat treatment was applied to samples at 1100C for 2 hours. Evaluation of the microstructures was conducted by optical microscopy. Corrosion morphology of samples were investigated by scanning electron microscopy and X-ray diffraction was used for the analysis of phases formed in the microstructure. Potentiodynamic polarization and electrochemical impedance spectroscopy methods in the 3.5 wt. % NaCl were used to evaluate the corrosion behavior of samples. Corrosion test results showed that by increasing the amount of titanium in the chemical composition, Hadfield steel shows less corrosion resistance. This is due to: 1- Ti leads to increasing the amount of carbides in the microstructure and formation of galvanic micro-cells. 2- Ti by increasing the amount of carbides leads to fine-grained structure and increasing number of grain boundaries. Also, scanning electron microscopy images indicated that increasing amount of Ti in the Hadfield steel composition, led to occurrence of micro-galvanic localized corrosion.