F. J. Martin

Carburization-Enhanced Passivity of PH13-8 Mo: A Precipitation-Hardened Martensitic Stainless Steel

Interstitial hardening of the martensitic stainless steel PH13-8 Mo has been achieved by low temperature gas-phase carburization. After treatment, hardness is increased to a depth of =50 μm, with a surface hardness that is twice the core hardness and a corresponding improvement in pin-on-disk wear resistance. Pitting potential is increased by ≈ 0.5 V in 0.6 M NaCl. Elemental analysis and X-ray diffraction suggest the formation of a thin (= 2 μm) carbidic surface layer that is both wear and corrosion resistant.

Chloride Interactions with the Passive Films on Stainless Steel

The uptake of chloride (Cl - ) by the passive oxide film on 316L austenitic stainless steel polarized at potentials below (less positive than) the pitting potential in 0.6 M NaCl solutions was studied using X-ray photoelectron spectroscopy (XPS) and compared to our previous work on aluminum. The XPS spectra for the stainless steel showed that chloride was not adsorbed or present in the passive oxide film. This is quite different from the case of aluminum, where XPS data for the presence of chloride on the surface and incorporated into the oxide film are unambiguous. These differences in the adsorption and incorporation of chloride for these two metals will be discussed in the context of the mechanisms of passive film breakdown.

Interstitial hardening of duplex 2205 stainless steel by low temperature carburisation: enhanced mechanical and electrochemical performance

Abstract The mechanical properties and corrosion resistance of duplex (ferrite–austenite) grade 2205 stainless steel have been substantially improved by interstitial hardening using low temperature carburisation. The austenite phase of the duplex stainless steel responds to low temperature carburisation in a similar manner as single phase austenitic stainless steels, forming ‘expanded’ austenite (also called S phase). The surface layer that forms on the ferritic portion of 2205 steel consists of a paraequilibrium carbide, a carbide with the same metal composition as the underlying ferrite. This two-phase case has about three times the Vickers hardness of non-treated material, an improved ultimate tensile strength and increased fatigue resistance, and much improved crevice corrosion resistance.

Interstitial hardening of type 316L stainless steel to improve corrosion resistance and mechanical properties

A low-temperature (450°C to 500°C), gas-phase interstitial hardening (IH) process that introduces substantial amounts of carbon, without carbide formation, into austenitic stainless steels was inve...