No abstract

Comparative studies of niobium carbide and niobium carbonitride coatings deposited on AISI 430 stainless steel have been presented. The NbC and NbCN coatings have been deposited by vacuum-arc evaporation in Bulat-type device by using the pulsed biasing mode with repetition frequency 50 kHz, allowing decreasing the micro-arcs formation. An additional magnetic coil for plasma flow focusing was used, allowing one to enhance deposition rate up to 35 µm/h. The phase composition of the obtained coatings was analyzed via X-ray diffraction. The surface morphology was monitored by scanning electron microscopy; whereas, chemical composition was examined by using energy dispersive X-ray analysis. X-ray fluorescent analysis was used to evaluate the thickness of the coatings. The reflectance R(λ) of the obtained coatings in the wavelength 300-625 nm at normal incidence was measured. The XRD data from NbC coating revealed the existence of the niobium carbide phase with a NaCl-type lattice with fine-crystalline grains ranging from 14 to 16 nm. For the NbCN coating, the two-phase state with c-NbC and hexagonal NbN 0.95 phases was monitored. The average grain size for c-NbC phase comprised 16-17 nm; whereas, for NbN 0.95 the average grain size was only 1-2 nm, confirming formation of a nanocrystalline structure. Surface nanomechanical behavior under nanoindentation of NbC and NbCN was studied. It was revealed that nanohardness for a NbC coating was varied from 30 to 43 GPa; whereas, for NbCN the data spread comprised 30-48 GPa. It was established that the surface of the grown coatings was very smooth with an extremely low amount of macroparticles.

No abstract

No abstract

No abstract