A. Zalar

Oxidation of TiN, ZrN, TiZrN, CrN, TiCrN and TiN/CrN multilayer hard coatings reactively sputtered at low temperature

Abstract All the coatings and multilayer structures were deposited in a Sputron plasma-beam-sputtering apparatus at a temperature below 150 °C on polished alumina substrates (Ra= 25 nm) and polished tool steel discs. The coatings were annealed in an oxygen flow at temperatures in the range 500–850 °C. The oxidation kinetics of these coatings were studied by means of the weight gain as a function of the oxidation time at each temperature. On the same coatings, continuous in situ electrical resistivity measurements were taken and these indicate grain boundary oxidation. The composition and the depth profiles of the oxidation products formed were investigated using AES and XPS combined with sputter profiling. The oxide layers were found to grow according to a parabolic diffusion law with activation energies of 1.04, 1.89, 1.92, 2.37,2.91 and 3.98 eV for Ti0.63Zr0.37N, TiN, CrN, ZrN, TiN/CrN and Cr0.72Ti0.28N, respectively.

Effect of chromium nitride coating on the corrosion and wear resistance of stainless steel

Abstract Ion beam-assisted deposition (IBAD) technique has been used to deposit chromium nitride on the stainless steel substrates. Characterization and performance of this coating was carried out by a round-robin test at various laboratories. About 300 samples, prepared at Spire, USA, were distributed to 10 different laboratories. Characterization of coated materials, carried out using Rutherford backscattering (RBS), X-ray diffraction (XRD), glancing X-ray diffraction, Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), confirmed a well-adherent layer of chromium nitride with composition and thickness of Cr0.8N0.2 and 1.2 μm, respectively. The performance of the coating was tested by tribological tests: dynamic micro-indentation, micro-hardness, wear and friction, and corrosion tests. The coating was found to be hard with good wear resistance and had enhanced resistance to corrosion in acid media.

High-temperature oxidation of TiN/CrN multilayers reactively sputtered at low temperatures

The high-temperature (600–850°C) oxidation of multilayer hard TiN/CrN coatings was investigated. TiN/CrN multilayer coatings (2.6 μm thick) with modulation periods in the range 83–425 nm were deposited at low temperatures (150°C) onto polished tool steel discs and polished alumina ceramic substrates (Ra = 25 nm) using the plasma-beam sputtering technique. The oxidation rate was obtained from the weight gain as a function of the oxidation time. The activation energy for oxidation of TiN/CrN multilayers was determined and compared with that for CrN, TiN and CrTiN coatings. The depth profiles of samples oxidized at various temperatures were examined by Auger electron spectrometry (AES) and glow discharge optical spectrometry (GDOS) to determine the thickness and the composition of the oxide layer. The morphology of the oxidized coatings was investigated by scanning electron microscopy (SEM). Continuous in-situ electrical resistivity measurements were performed on the same coatings to detect grain-boundary oxidation. The adhesion and microhardness of the multilayers were also determined.

OXIDATION BEHAVIOUR OF TIALN COATINGS SPUTTERED AT LOW TEMPERATURE

Abstract The basic mechanical and structural properties, as well as the oxidation behaviour of Ti 1- x Al x N coatings sputtered at low temperature are reported. Ti 1- x Al x N coatings of four different compositions were sputter deposited in a Sputron (Balzers) plasma-beam sputtering apparatus at a temperature below 200°C. Polished tool steel discs, silicon wafers and polished alumina ceramics were used as substrates. Oxidation of coatings was carried out by heating the samples at temperatures of 700–900°C in an oxygen atmosphere for selected times. The surface and fracture cross-sectional morphology of the as-deposited and oxidized films were studied by scanning electron microscopy, while the structure of the coatings was examined by the XRD and TEM techniques.

A method of studying carbon particle distribution in paint films

Abstract The process of dispersion of pigment particles within the resinous component of the system is one of the most important parameters in the manufacture of any surface coating. Determining the degree of pigment dispersion is of fundamental importance, since it affects the optical, color strength and rheological properties of a paint system. In the present paper we describe a method of treatment of carbon black paint film which enables the determination of distribution of carbon black particles in the film. The method is based on selective etching of the paint using a low pressure weakly ionized highly dissociated oxygen plasma. At the pressure of 50 Pa, the neutral gas temperature of approximately 50°C, the electron temperature of 5 eV, the density of charged particles of 2×10 15 m −3 and the density of neutral oxygen atoms of 4.4×10 20 m −3 , high selectivity of etching is obtained. At these conditions, optimal time of etching is approximately 30 s. The etching is due mainly to interaction of neutral oxygen atoms with surface carbon atoms and the probability for interaction is estimated to 0.026.

Recombination of neutral oxygen atoms on stainless steel surface

Abstract The recombination coefficient of neutral oxygen atoms on polycrystalline AISI 304 stainless steel surface was determined experimentally. The source of neutral oxygen atoms was an inductively coupled RF oxygen plasma. The density of oxygen atoms was determined with a nickel catalytic probe and was between 3×10 19 and 2×10 21 m −3 . A virgin stainless steel disc was activated by exposure to atomic oxygen at the density of 1.5×10 21 m −3 for 120 s. During the activation, a layer of oxide with the thickness of about 10 nm was formed on the surface. After successful activation, the temperature of the stainless steel disc during exposures to atomic oxygen was measured at different O density and different pressure in the system. It was found that the recombination coefficient was a constant at the value of 0.070±0.009.

Interfacial reactions in Al2O3/Ti, Al2O3/Ti3Al and Al2O3/TiAl bilayers

Abstract Interfacial reactions were studied at three different heat-treated oxide/metal bilayers (oxide: amorphous a-Al 2 O 3 and metal: crystalline c-Ti, Ti 3 Al or TiAl) by means of AES depth profiling. The different oxide/metal bilayers were sputter deposited on smooth silicon substrates, covered with a TiN thin-film diffusion barrier. The reactions at the oxide/metal interfaces were activated in a differential scanning calorimeter by heating the samples in an argon atmosphere at a linear heating rate of 40°C/min, between room temperature and different final temperatures (350 to 700°C). In order to characterize the reaction products, i.e. solid solution of oxygen in the α -Ti and the newly formed α 2 -Ti 3 Al phase, XPS and TEM investigations were performed on selected samples. The thermal stability of three interfaces was investigated in dependence of aluminium content and consequently with respect to the solubility of atomic oxygen in the metallic layers. Thermodynamic calculations revealed that the heat of solution of oxygen in the metallic layers is crucial for the interfacial reactions. The experimental results are consistent with thermodynamic data: the a-Al 2 O 3 /c-Ti interface shows the highest reactivity, followed by the a-Al 2 O 3 /c-Ti 3 Al interface. In the a-Al 2 O 3 /c-TiAl bilayer no reaction was detected at the interface, indicating thermal stability up to 700°C. The mechanism of the chemical reaction at the interfaces of the different bilayers is discussed

Characterization of intermetallic phases and oxides formed in annealed NiAl multilayer structures

Abstract Two different multilayer structures composed of ten alternating Ni and Al thin films were sputter deposited on Si (111) substrates. These multilayers with individual Ni and Al thin film thicknesses of about 25 nm and 38 nm and of 25 nm and 13 nm, respectively, have the average compositions of Ni0.50Al0.50 and Ni0.75Al0.25. The samples were heat treated in a differential scanning calorimeter instrument with a constant heating rate of 40 °C min −1 in Ar from room temperature to 550 °C. The compositions of as-deposited and heat-treated samples were studied with high-resolution Auger electron spectroscopy (AES) rotational depth profiling. X-ray photoelectron spectroscopy (XPS) analyses show an excess of Ni in both annealed samples. X-ray diffraction measurements of annealed multilayers show the formation of Ni2Al3 and NiAl3 phases in the Ni0.50Al0.50 sample and the presence of Ni3Al and Ni A13 phases with some excess of Ni in the Ni0.75Al0.75 sample. AES and XPS investigations of the reacted layers after 15 min annealing in air at 500 °C disclose considerably different surface oxide thin films: on the Ni0.50Al0.50 layer the oxide thin film consists of Al2O3 with a small amount of NiO, whereas that on the top of the Ni0.75Al0.25 layer is thicker and consists of NiO on top and some Al2O3 below.

Recombination of neutral hydrogen atoms on AISI 304 stainless steel surface

Abstract The recombination coefficient of neutral hydrogen atoms in the ground state on polycrystalline AISI 304 stainless steel surface was determined experimentally. The H source was an inductively coupled RF hydrogen plasma with the density of 1016 m−3 and the electron temperature of 6 eV. The gas from the discharge vessel was leaked into another vessel through a Schott 8250 glass tube with the inner diameter of 5 mm and the length of 6 cm. Charged particles created in the discharge vessel were effectively recombined on the walls of the glass tube, so that the gas entering the experimental chamber was solely a mixture of neutral hydrogen atoms and molecules. The density of hydrogen atoms in the experimental chamber was measured with a well activated nickel catalytic probe. The H density depended on pressure in the discharge vessel and was between 3 and 19×1020 m−3. The nickel catalytic probe was replaced with an identical probe made of stainless steel. After successful activation of the stainless steel surface, the signal due to atomic hydrogen recombination was measured at different pressure. Comparing the results obtained with the nickel probe and the stainless steel disc enabled determination of the recombination coefficient for the reaction 2H→H2 on polycrystalline stainless steel surface: γ=0.10.

Auger electron spectroscopy depth profiling studies on stationary and rotated samples of a new model metal/semiconductor multilayer structure

Abstract Multilayer structures for application in microelectronics are becoming increasingly complex. A sputter deposited multilayer structure composed of chromium, nickel and silicon layers with a total thickness of 310 nm on a smooth silicon substrate was characterized by transmission electron microscopy (TEM) and by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) depth profiling. AES depth profiles of the Ni/Cr/Si multilayers were obtained with Ar + ion bombardment at various angles of incidence using stationary and rotated samples. In some cases a strong influence of semiconductor structure on the experimentally obtained metal-metal and metal-semiconductor interface widths was observed. Owing to ion beam induced Si(LVV) Auger electrons in the crater wall of the Ni/Cr/Si sample, a distortional influence on depth resolution during simultaneous AES analysis and ion sputtering was found. Silicide formation during sputtering at the silicon-metal interfaces was confirmed by XPS. The measured compositional depth profiles are explained with respect to the influence of polycrystalline metallic and amorphous semiconductor structures; the effects of ion beam induced topography, atomic mixing and silicide formation are discussed.