Pulsed laser deposition technique was applied for covering elastic cast-polyurethane membranes with titanium nitride and boron nitride layers. The deposition process was realized using a Nd:YAG laser with Qswitch in stages; firstly the membranes were coated with ultra-thin titanium nitride layer (TixN) by evaporation of a metallic titanium disk in nitrogen gas atmosphere and then a layer of boron nitride (BN) was deposited by ablation of hexagonal h-BN target in argon atmosphere. The surface morphology was observed by scanning electron microscopy. Chemical composition was analyzed by energy dispersive X-ray spectrometry. The phase analysis was performed by means of grazing incidence X-ray diffraction and attenuated total reflection infrared spectroscopy. The crystallographic texture was measured. The wear test was performed by pin-on-disk method. Hexagonal boron nitride layers with (0001)[uvtw] texture with flake-like grains were fabricated. The structure and texture of boron nitride was identical irrespectively of substrate roughness or BN thickness. Pin-on-disk wear tests showed that the coatings effectively decreased the friction coefficient from two to even four times comparing to pure polyurethane and polyurethane covered with graphite. This proved that deposited layers can replace graphite as a lubricating material used to protect polymer surfaces.
Boron nitride thin layers were produced by means of the pulsed laser deposition technique from hexagonal boron nitride target. Two types of laser i.e. Nd:YAG with Q-switch as well as KrF coupled with RF generator were used. Influence of deposition parameters on surface morphology, phase composition as well as mechanical properties is discussed. Results obtained using Fourier Transformed Infrared Spectroscopy, Transmission and Scanning Electron Microscopy, Atomic Force Microscopy are presented. Micromechanical properties measured during microindentation, scratch and wear tests are also shown.
In view of their advantageous properties (high hardness, good frictional wear resistance, chemical and thermal stability at elevated temperatures), cubic boron nitride (cBN) and tungsten carbide (WC) are commonly used for the fabrication of cutting tools. The composites were consolidated at a temperature of 1100°C under a load of 100 MPa for 10 min. The density of the thus produced material was close to the theoretical value (about 99.6%), and the hardness HV30 was about 1950. The phases identified in the composite were WC, Co, and cBN. Microstructural examinations revealed that numerous trans-crystalline fractures through the cBN particles occurred in the material. The present study is concerned with the wear of the WCCo and WCCo/cBN composites. Comparative tribological examinations were performed in a tribological tester using the ball-on-disc arrangement under the conditions of dry friction. The counterspecimens were steel and Al2O3 balls. The tests were conducted under a unit load of 10 N. After the tests, the surface of the samples was examined to describe the wear mechanisms active in various composite materials.