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

Plasma nitriding is an effective surface treatment to improve unsatisfactory wear properties of machine elements. Such machine elements may also subject to magnetic fields in many industrial applications. Therefore, AISI 4140 ferromagnetic steel samples were plasma nitrided. Then, the samples were quenched in water and then post-aged at a temperature of 400°C for 30 and 120min in plasma environment. Reciprocating wear tests were performed under different oriented DC magnetic field to determine wear behavior of the samples. It was obtained that the magnetic field and its orientation during wear test were the most effective parameters on wear behavior. It was observed that post-aged samples showed better wear resistance and lower friction coefficient values than the merely nitrided samples. Hard Fe16N2 precipitations were formed in the nitrided layer after post-aging treatment and their amount increased with magnetic field. This gave rise to improvement the wear resistance.

Albayrak, Çiǧdem; Hacisalihoǧlu, Ilyas; Yenal vangölü, S.; Alsaran, Akgün

Commercially pure titanium (CP Ti) is widely used as an implant material, which has excellent corrosion resistance and high biocompatibility. However, pure Ti has poor tribological properties. For this reason, surface modification techniques and/or surface coatings have been applied on implant materials. For instance, plasma nitriding processes have been used to obtain protective coatings on pure Ti implants in order to improve their wear resistance and durability. In this study, a plasma nitriding process was applied on pure Ti substrates, which formed a hard compound layer consisting of TiN and Ti2N phases. An anodizing process was implemented on nitrided samples, which created a porous TiO2 oxide layer. Tribocorrosion tests were carried out with a reciprocating tribometer combined with a three-electrode cell. Tests were performed at open circuit potential (OCP), potentiostatic and potentiodynamic studies condition in Simulated Body Fluid (SBF). The OCP value and friction coefficient of duplex treated specimen under wear conditions were better compared to the other samples; nevertheless it was observed that the wear and the wear products were more effective during tribocorrosion tests.