Çakir, M. Aslan

The structure, phase composition, wear resistance, and electrochemical behaviors of oxynitride films on the surface of austenitic 316L stainless steel substrates formed via plasma oxynitriding using gas mixtures of different compositions are studied. Plasma oxynitriding is carried out at a temperature of 425 °C for 2 h at various ratios of the gas mixtures, i.e., 25% O2 – 75% N2, 50% O2 – 50% N2, 75% O2 – 25% N2. The structure of the coatings is studied by scanning electron microscopy and x-ray diffraction. The wear resistance of the films is evaluated by sliding an alumina ball under dry conditions and in an SBF environment simulating body fluid conditions. The corrosion resistance of the films is determined in the SBF medium. It is shown that the formation of the S (111) and S (200) phase layer upon oxynitriding of steel 316L increases its wear and corrosion resistances. The films formed during the treatment at the gas ratio of 75% O2 – 25% N2, have the highest properties.

Bayrak, Ö.; Kovaci, H.; Yildiz, F.; Yetim, A.F.; Çelik, A.

Forged low-carbon alloy Co – 27% Cr – 6% Mo – 0.06% C is studied after 2-h plasma nitrocarburizing in a gaseous mixture of 10% CO2 + 20% N2 + 70% H2 at 400, 500 and 600°C. The surface layer and the core are studied by diffractometric analysis and scanning electron microscopy. The microhardness and the tribological characteristics of the alloy are determined. The effect of the temperature of nitrocarburizing on the wear resistance, surface roughness and friction coefficient of the alloy is considered.

Kovací, Halim; Ghahramanzadeh, Hojjat; Albayrak, Çigdem; Alsaran, Akgün; Çelik, Ayhan

The effect of the temperature and duration of plasma nitriding on the microstructure and friction and wear parameters of Inconel 718 nickel alloy is investigated. The process of plasma nitriding is conducted in a nitrogen- hydrogen gaseous mixture at a temperature of 400, 500 and 600°C for 1 and 4 h. The modulus of elasticity of the nitrided layer, the micro- and nanohardness, the surface roughness, the friction factor and the wear resistance of the alloy are determined prior to and after the nitriding. The optimum nitriding regime providing the best tribological characteristics is determined.