Structure related corrosion behavior of DLC films in high Cl− environment

The diamond-like carbon (DLC) films were successfully fabricated on the surface of 13Cr super martensitic stainless steel by plasma enhanced chemical vapour deposition, and the microstructure changed with the variation of pulse voltages of the high pulse power supply. The microstructure of the DLC films was characterized by atomic force microscope, and the corrosion behavior of the films in a high Cl− environment was analyzed by open circuit potential, polarization curve and electrochemical impedance spectroscopy. It is found that the substrate corrosion occurred first for the DLC films with open pores, followed by a substrate surface passivation before the final corrosion failure. The DLC film with closed pores can effectively prevent Cl− from attacking the substrate before the corrosion pits formed at the local defects.

Fatigue strength evaluation of a 13%Cr supermartensitic stainless steel by the thermographic method

The fatigue limits of a 13Cr super-martensitic stainless steel from a hot rolled seamless tube were determined for three heat treatment conditions, including the as received quenched and tempered (QT) condition, quenched (Q), and quenched and double tempered (Q-DT). These heat treatments were applied to produce different microstructures and different tensile mechanical properties. The microstructures were characterized by microscopy and magnetic methods. The fatigue strength was accessed through the utilization of the thermographic technique. The results show that fatigue limits measured were between 38% and 44% of the ultimate strength. The as quenched condition gave the higher fatigue limit (444 MPa). However, the material has the lower dutility at this condition. The results aid to decide the best heat treatment condition and give support to design in applications where dynamic loadings are expected