Tomasz Suszko

This study examines the structure and properties of NiMo-C coatings synthesized via reactive magnetron sputtering of a NiMo alloy target in an argon/acetylene atmosphere. The coating structure evolves with carbon content from nanocrystalline, through amorphous to quasi-amorphous with a nanocolumnar structure. The nanostructure consists of metallic columns perpendicular to the substrate surrounded by an amorphous carbon shell. The coatings are evaluated for their potential use as catalytic materials in the hydrogen evolution reaction (HER) in an acidic environment. The medium carbon content coatings show optimal properties in this direction, i.e., high corrosion resistance in an acidic environment and good HER performance described by the Tafel slope and characteristic overpotentials. Even at the highest carbon content, 74 at. %, the Tafel slope does not increase substantially, which is more likely attributable to the distinctive nanocolumnar structure, ensuring the presence of catalytic centers in the form of metallic islands on the surface. At the highest current densities applied, a weak but visible correlation is observed between the characteristic overpotentials and the contact angle hysteresis derived from the wettability measurements.

The purpose of the study was to ascertain the corrosion resistance in Hanks’ solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating thickness as well as the correlated effect of the metallic sublayer type and defects present in DLC films on corrosion propagation were discussed. The results obtained were compared with findings on the adhesion of DLC to the steel substrate. The synthesis of carbon thin films with Cr and Ti adhesive sublayers was performed using a combined DC and a high-power-impulse vacuum-arc process. Evaluation of the corrosion resistance was carried out by means of potentiodynamic polarisation tests and scanning electron microscopy. Adhesive properties of the sublayer/DLC coating systems were measured using a scratch tester. It was found that systems with Ti sublayers were less susceptible to the corrosion processes, particularly to pitting. The best anti-corrosion properties were obtained by merging Ti with a DLC coating with a thickness equal to 0.5 μm. The protective properties of the Cr/DLC systems were independent of the carbon coating thickness. On the other hand, the DLC coatings with the Cr sublayer showed better adhesion to the substrate.

The article presents a complex system of design, in situ visualization and control of the commonly used surface treatment process: the gas nitriding process. In the computer design conception, analytical mathematical models and artificial intelligence methods were used. As a result, possibilities were obtained of the poly-optimization and poly-parametric simulations of the course of the process combined with a visualization of the value changes of the process parameters in the function of time, as well as possibilities to predict the properties of nitrided layers. For in situ visualization of the growth of the nitrided layer, computer procedures were developed which make use of the results of the correlations of direct and differential voltage and time runs of the process result sensor (magnetic sensor), with the proper layer growth stage. Computer procedures make it possible to combine, in the duration of the process, the registered voltage and time runs with the models of the process.