Modification of carbon steel surface by the Tenifer® process of nitrocarburizing and post-oxidation

Abstract

The surface of the non-alloyed carbon steel was subjected to thermo chemical modification by salt bath nitrocarburizing with or without post-oxidation based on the Tenifer procedure in order to improve mechanical properties, corrosion and wear resistance. Nitrocarburized layers were characterized by testing their basic properties (compound layer thickness, nitrocarburizing depth, surface hardness) according to current standards. Detailed estimation of the quality of the modified metal surface was performed by additional testing of chemical compositions by EDX and X-ray diffraction, microstructure, surface roughness and topography, and corrosion resistance. The corrosion resistance was investigated in a water solution of 5% NaCl using electrochemical polarization methods and electrochemical impedance spectroscopy. The corrosion properties of the treated and non treated samples are compared among themselves and with the properties of austenitic steel. The surface layer obtained after nitrocarburization treatment consists mainly of ε-Fe2-3N and γ'-Fe4N. The surface layer of the samples after post-oxidation consists also of ε-Fe2-3N and γ'-Fe4N, but contains additionally Fe3O4. The results obtained show that nitrocarburizing and post-oxidation treatments, based on the Tenifer procedure, result in better mechanical and corrosion properties of nonalloyed carbon steel. The corrosion properties of the thermo chemically modified nonalloyed carbon steel were improved and approach the corrosion properties of austenitic steel, known for its very good corrosion resistance.

Corrosion resistance of surface treated 42CrMo4 steel

“…To the corrosion resistance has a significant influence the thickness and the surface layer composition obviously. The Arcor , a nitrocarburizing process in the salt bath, was followed by a post-oxidation process to form a thin and compact Fe 3 O 4 oxide layer covering the pores in the tie-layer [15]. This surface layer is especially resistant to abrasion, corrosion and galling as well [16].…”

Phase Transformations during Low Temperature Nitrided Inconel 718 Superalloy

“…19) For the corrosion resistant alloy, the conventional nitriding cannot be used because it is well established that nitriding of alloys containing Cr above 500°C produces undesirable CrN that degrades the corrosion resistance. 16) Thus the treatment temperature must be lower.…”

“…Most of the research was focused on plasma nitridization, gas nitridization, plasma carburization and gas carburization of different alloys. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] However, much less attention have been paid to nitridization of nickel based superalloys, in that such alloys are difficult to be nitrided. 20,21) This is due to the formation of passivated oxide layer on the surface, which impedes the infusion of alloying elements.…”

“…22) Moreover, the salt bath nitriding was a highly effective and low-cost method with many advantages such as low nitriding temperature, short treatment time, high degrees of shape and dimension stabilities, and easy reproducibility. [19][20][21][22][23] However, the liquid phase nitriding was considered harmful to the environment by lots of researchers. The truth is that the main components of the conventional liquid phases for nitriding comprise urea, carbonate, chloride and some nontoxic trace components.…”

Tribological Comparison of Traditional and Advanced Firearm Coatings

“…The surface layer consists of ε-Fe 2-3 N and γ'-Fe 4 N. (58) The nitrogen and carbon content decreases continuously from the edge towards the core, as a result of nitrogen diffusion. The corrosion resistance is also better for iron and conventional steel, but not for stainless steel.…”