An investigation of pitting initiation mechanism of 1Cr12Ni2W1Mo1V steel after induction hardening

Pitting potential of the 1Cr12Ni2W1Mo1V steel specimens, which is hardened and tempered at different temperatures, was measured under different corrosion environments and different stress levels. Test results showed that the external stresses have great influence on the pitting initiation of the 1Cr12Ni2W1Mo1V steel besides the material processing, microstructure and corrosion environments. Pitting potentials increase with decreasing of the concentration of chloride ion and have a linear relationship with log CCl. Under a certain concentration of chloride ion, the effects of pH on the induction-hardening specimens after low temperature tempering are negligible, while the effect of pH on the high temperature tempered specimen is relatively great. Pitting potentials decrease dramatically with the increasing of the stress when the stress is lower than 50 MPa; pitting potentials decrease little with the increasing of the stress in the region of 50–400 MPa; pitting potentials tend to be stable when the stress is higher than 400 MPa. Based on the test results, a Subscriptematical expression of passive film cracking coincides with the experimental results. Heat treatment have great effects on the corrosion resistance of 1Cr12Ni2W1Mo1V steel.