D. Zhong

Mechanical properties of Ti-B-C-N coatings deposited by magnetron sputtering

Abstract This work investigated structure, mechanical properties and tribological performance of the Ti–B–C–N thin films deposited using RF magnetron sputtering in different argon–nitrogen atmospheres from a TiB2–TiC composite target synthesized by a one-step SHS-consolidation technique. Quasi-amorphous nano-composite films were deposited using RF power density of 11.2 W/cm2 and a substrate bias of −50 V. In this paper, the mechanical properties of the composite films, including nanohardness, Youngs modulus, film adhesion and residual stress, are presented together with their tribological behavior. The best properties and performance were achieved by depositing the film with a 50-nm-thick titanium interlayer and using a substrate bias of 50 V. The nitrogen content in the deposition atmosphere changed the film properties and performance slightly. The Ti–B–C film and the Ti–B–C–N film deposited in an argon–nitrogen atmosphere with 10% nitrogen exhibited the best adhesion to substrate, lowest residual stress, and best tribological performance. In general, these Ti–B–C–N thin films appear to be a promising composite film system suitable for engineering wear applications.

Composition and oxidation resistance of Ti–B–C and Ti–B–C–N coatings deposited by magnetron sputtering

Abstract Nanocomposite Ti–B–C and Ti–B–C–N coatings were deposited from a TiB 2 –TiC target using RF magnetron sputtering. In this paper, the composition and oxidation kinetics of Ti–B–C and Ti–B–C–N coatings are presented. The film composition was characterized using XPS. Compared to the target composition, preferential sputtering of the carbon component was observed. Introducing nitrogen into the sputtering gas resulted in the formation of TiN, with nitrogen of approximately 30 at.%, and shifted the C 1s peak from the typical position for carbide to a higher binding energy position, which is typical of graphite. Both dynamic and isothermal oxidation kinetics were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The oxide compositional depth profile, structure and morphology were characterized by Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that: (1) catastrophic oxidation started at 920 K; (2) TiB 2 and TiC in Ti–B–C coatings oxidized in sequence; (3) isothermal oxidation of Ti–B–C coatings in the temperature range from 1173 to 1323 K obeyed a parabolic rate law with an activation energy of 1.64 eV/atom, indicating a diffusion-controlled mechanism; and (4) well-crystallized oxide scales formed after oxidation in air at 1173 K for 2 h are mainly rutile TiO 2 , with XRD-detectable hexagonal B 2 O 3 and hematite Fe 2 O 3 resulting from iron outward diffusion.

Wettability of NiAl, NiAlN, TiBC, and TiB–CN films by glass at high temperatures

Abstract The sticking/adhesion of glass to glass molding dies and forming tools is a critical problem which limits the quality of glass products and the performance and reliability of molding dies and forming tools. Depositing NiAl, NiAlN, TiBC, and TiBCN coatings and characterizing their wettability by glass at high temperature are part of an overall program that is being conducted to develop a non-sticking, oxidation resistant, and wear resistant coating system for glass molding dies and forming tools. The use of contact angle analysis for evaluation of wettability is described in this paper. The contact angles were measured by the sessile drop technique and analyzed by an image analyzer. The film microstructures were studied using cross-sectional TEM technique. Factors affecting the wettability are discussed. NiAl and NiAlN films seemed to offer more potential than TiBC and TiBCN films in terms of non-wettability by glass at high temperatures, they are promising ‘working’ layers for glass molding dies and forming tools.

Microstructure and mechanical properties of superhard Ti–B–C–N films deposited by dc unbalanced magnetron sputtering

Superhard quarternary Ti–B–C–N films were successfully deposited on AISI 304 stainless steel substrates by a dc unbalanced magnetron sputtering technique from a Ti–B–C composite target. The relationship between microstructures and mechanical properties was investigated in terms of the nanosized crystallites∕amorphous system. The synthesized Ti–B–C–N films were characterized using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). These analyses revealed that our Ti–B–C–N films are composites of solid-solution (Ti,C,N)B2 and Ti(C,N) crystallites distributed in an amorphous boron nitride (BN) phase including some of carbon, CNx, B2O3 components. The hardness of the Ti–B–C–N films increased with the increase of N content up to a maximum value of approximately 45 GPa at 10 at. % N, with a subsequent decrease in hardness at higher N content. This value is considerably higher than the hardness measured in our Ti–B–C films (∼35GPa). The Ti–B–C–N(10 at .%)...

Deposition and characterization of NiAl and Ni-Al-N thin films from a NiAl compound target

Abstract NiAl and Ni–Al–N thin films have been deposited from a dense and homogeneous NiAl compound target onto various substrates, including stainless steel, glass, and Si 100 wafer, by using RF magnetron sputtering. The films have been characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and scanning transmission electron microscopy. Both the NiAl and Ni–Al–N thin films exhibited the near equiatomic NiAl phase. The Ni–Al–N thin films showed an increasing nitrogen content with increasing the amount of N2 in the sputtering atmosphere during deposition. XPS spectra confirmed the possible formation of aluminum nitride in the Ni–Al–N films. The texture, composition, and microstructure of the NiAl films change with the discharge power used. The NiAl thin films deposited using 500 W RF power exhibited the microstructure of a 0.5–0.7-μm amorphous layer adjacent to the substrate and a dense and columnar zone T crystalline microstructure which had a preferred orientation [110]. The Ni–Al–N films showed a homogeneous microstructure of very fine (nano scale) NiAl (110) grains distributed into an amorphous matrix. The results confirm the feasibility of producing high-quality NiAl and Ni–Al–N thin films from a NiAl compound PVD target.

Finite element analysis of a coating architecture for glass-molding dies

Finite element analysis (FEA) is being used as an integral part of an overall research program that is being conducted to develop a non-sticking, oxidation- and wear-resistant coating system for glass-molding dies and forming tools. This non-linear thermomechanical FEA consists of two parts: (1) a global analysis using a coupled thermomechanical model of the complete die to predict the locations where the die experiences extreme stress/strain condition during molding cycles; and (2) a local analysis of the die coating used to protect the die at those positions where extreme conditions were predicted by the global analysis, to analyze the stresses generated in the coating system during a simulated glass-molding process. This paper outlines the methodology developed in this work, which can be used to explore the effects of die geometry, die material, and coating materials on the integrity, reliability and performance of a coated die. This methodology may also be helpful for investigation of the mechanisms relating to the thermal fatigue problem. The preliminary results presented here demonstrate that it is possible to find an optimized coating architecture with optimal stress transition from the substrate to the outmost working layer by selecting appropriate coating materials and engineering the compositional gradients of the functionally graded material (FGM) intermediate layer.

Effect of Pulsed Plasma Processing on Controlling Nanostructure And Properties of Thin Film/Coatings

Abstract The benefits of pulsed plasma processing, including pulsing both cathode and substrate in physical vapour deposition (PVD) processes (magnetron sputtering and cathodic arc evaporation (CAE)) and the pulsed plasma enhanced chemical vapour deposition (P-PECVD) process were demonstrated by correlating the pulsed plasma process parameters, microstructure and properties. Five coating systems were developed for structural, electronic, functional and tribological applications. These are: pulsed reactive magnetron sputtering of TiO thin films; alumina deposition with pulsed plasma in closed field unbalanced magnetron sputtering; deposition of thin film silicon using P-PECVD; high energy pulsed bias assisted CAE of Cr–N graded coatings on 7075-T6 Al substrates; and sputter deposition of nickel anode on protonic BaCe0.9Y0.1O3–a electrolyte under pulsed dc biasing of substrate. Pulsed plasma was found to change particle energies and plasma composition in both PVD and CVD processes. Through controlled ion bombardment (ion energies and relative abundances of plasma species) by varying pulse frequency, pulse duration and bias voltage, film growth and therefore film properties can be tailored. The films became denser and nanostructured. The interface structure was graded, allowing superior adhesion. Better film performance (e.g. wear resistance, fracture toughness and efficiencies of solar cells and fuel cells) was achieved because of the modified film microstructure and architecture. These results clearly indicate the significant effects of the plasma species and their energies on modification of both the structure and properties of thin films. In several of these examples, the properties could not have been achieved in continuous dc magnetron sputtering. SE/518

Nanocomposite Coating Systems Tailored for Specific Engineering Applications

Nanostructured PVD coatings in the Cr-N, Ni-Al-N, Ti-B-C-N, and Ti-Al-Si-N systems exhibit superior properties and have been tailored for specific engineering applications. These examples demonstrate that ion bombardment (ion energies and relative abundances of plasma species) of the substrate controls the relative amount of constituent phases of a nanocomposite and its crystallite size, and determines the microstructure (including crystal structure, interfacial structure, and grain structure) evolution during film growth. Through engineering the composition and microstructure, the desired relative density, mechanical, physical and chemical properties of the resulting film were obtained.