The subject of the study concerns the enhancement of corrosion and wear resistance of nitrided 42CrMo4 steel by the formation of zinc phosphate top layer. The present work is aimed at the assessment of the effect of increasing thickness of nitrided layer from approximately 2 µm to 16 µm on the morphology and properties of zinc phosphate coating. XRD analysis showed that along with the increase in the thickness of the nitrides layer, a change in the phase composition was observed. SEM/EDS examination revealed that top layer consists of crystalline zinc phosphate coating. The shape and size of crystals does not significantly depend on a thickness of nitrides layer but corrosion resistance determined by potentiodynamic method in 0.5M NaCl increased with an increase of thickness of a “white layer”. Similarily the wear resistance determined by the 3-cone-roll test was also the highest for 16 µm nitride layer.
Nitrogen-doped DLC (diamond-like carbon) coatings were produced on 316L nitrided austenitic steel in direct current and pulsed glow discharge conditions. The chemical composition, surface topography, hardness and corrosion resistance of the obtained carbon coatings were examined. The coatings varied in surface morphology, roughness and hardness. Direct current glow discharge made it possible to produce a coating characterized by lower hardness, greater thickness and higher nitrogen content. The coating featured improved corrosion resistance and adhesion compared to coatings produced in the pulsed process.
The oral cavity due to its temperature fluctuations, changing pH, high humidity, action of mechanical forces and the presence of microorganisms is a favorable environment for degradation of dental materials. The paper presents comparative results on orthodontic arch-wires AISI304 steel before and after low temperature plasma nitriding carried out at cathodic potential (conventional) and at plasma potential, i.e. in a process incorporating an active screen. Corrosion resistance test on nitrided layers produced on stainless steel were carried out via electrochemical impedance spectroscopy (EIS) and the potentiodynamic method in non-deaerated artificial saliva solution at 37°C. The results were complemented with analysis of the structure, surface topography and microhardness. The results showed an increase in corrosion resistance of AISI304 steel after conventional glow-discharge nitriding.