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Ti-doped diamond-like carbon (Ti-doped DLC) films were deposited on 304 stainless steel through a pulsed filtered cathodic vacuum arc deposition with an individual cathodic arc source. Structural dependent thermal stability, mechanical properties, adhesion, and corrosion performance were thoroughly investigated as a function of the Ti content. Only 0.8 at.% Ti content in the DLC films offers the relatively high hardness (28.8 GPa), high corrosion resistance, enhanced adhesion strength as well as improved thermal stability compared to the undoped DLC films. The reduction in the internal stress and the sp3 content associated with a slight decrease in the mechanical properties is from Ti doping. Higher thermal stability is due to the TiC phase in the Ti-doped DLC structure. Enhancement of the adhesion strength is owing to the relief of the internal stress and the occurrence of the strong atomic intermixing bond at a Ti-doped DLC/Ti intermediate layer interface. Interestingly, the formation of the TiO2 film on the Ti-doped DLC surface due to a small amount of Ti doping significantly exhibited a better corrosion performance. Ti-doped DLC films, therefore, are a promising coating for tribological applications.

Titanium was incorporated and interlayered into diamond-like carbon (DLC) films deposited on 316L stainless steel using a filtered cathodic vacuum arc. The local bonding structure, corrosion, and biocompatibility of non-doped DLC (ta-C), Ti-interlayered (ta-C/Ti), Ti-doped (ta-C:Ti), and Ti-doped and Ti-interlayered (ta-C:Ti/Ti) DLC films were thoroughly investigated. ta-C:Ti/Ti (0.55 at.%Ti) exhibited not only the highest corrosion resistance performance, including the lowest corrosion rate (7.34 × 10−8 mm yr−1), the highest pitting potential (1672.97 mV), and the highest polarization resistance (5.97 MΩ cm2), owing to the formation of TiO2 on its surface, as confirmed by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, but also the highest amount of hydroxyapatite, an indicator for biocompatibility, on its surface as determined with Fourier transform infrared spectroscopy and scanning electron microscopy. Two barrier layers, namely, outer and inner layers, were observed in ta-C/Ti and ta-C:Ti/Ti, while only one barrier layer was in ta-C and ta-C:Ti, as demonstrated by electrochemical impedance spectroscopy. Therefore, ta-C:Ti/Ti is an alternative promising DLC film for joint replacement biomaterials.

Al and N were incorporated into diamond-like carbon (DLC) films deposited using a filtered cathodic vacuum arc on AISI 4140 low-alloy steel. The structure, nanomechanical properties, local bonding, and thermal stability of non-doped DLC (ta-C), Al- and N-doped (ta-C:Al and ta-C:N), and Al- and N-co-doped (ta-C:Al:N) films were thoroughly investigated. The thermal stability of the deposited films was measured using radiative heating and electron beam bombardment under a vacuum during thermal annealing. In-situ near-edge X-ray absorption fine structure spectroscopy was performed to characterize the surface nanostructures at different temperatures. ta-C:Al:N exhibited not only high hardness (49.04 GPa) and high (58.43%) elastic recovery (ER)—approximately equal to those of non-doped DLC films: 51.12 GPa and 60.06% ER, respectively)—but also higher thermal stability than ta-C at ~600 °C owing to the synergy of Al2O3 and sp3 N-C bonds formed in the DLC films, as confirmed by X-ray photoelectron spectroscopy. ta-C:Al:N, therefore, is a suitable coating for wear and tribological applications, especially at high temperatures.

A cemented carbide end mill was coated with AlCrTiSiN film by cathodic arc physical vapor deposition methods (CAPVD). A performance of AlCrTiSiN film for increasing tool life was evaluated by scratch test, cutting test and oxidation test in comparison with uncoated end mill. From the scratch test, the AlCrTiSiN film was helpful to resist crack and delamination of coating. From the cutting test, the maximum flank wear of AlCrTiSiN film was about two times higher than that of the uncoated end mill resulting in tool life extension. From the oxidation test, the first oxide of AlCrTiSiN film generated after service life was a titanium dioxide (TiO2) at a temperature of 900oC. From all of results, it revealed that the AlCrTiSiN film significantly enhanced the tool life of the cemented carbide end mill.

The objective of this research is to study wear behaviors of TiN, nanolaminated AlCrN and nanocomposite TiAlSiN coated on cemented carbide end mill deposited by cathodic arc physical vapor deposition methods in comparison with uncoated end mill. Wear behaviors were investigated by nanoindentation hardness test, scratch test and cutting test. Oxidation test was also done in air at temperatures of 700°- 900°C in order to evaluate resistance of oxidation. In the nanoindentation hardness and scratch tests, nanocomposite TiAlSiN coating exhibited higher hardness than TiN and nanolaminated AlCrN coatings. The nanolaminated AlCrN coating represented the highest adhesion ability in terms of critical load and the lowest coefficient of friction in comparison with the TiAlSiN and TiN coatings, respectively. The cutting performance, represented in terms of maximum flank wear as a function of cutting length, was found to be highest in the AlCrN coating. Oxides of these coatings, i.e., TiO2 for TiN, TiO2 for TiAlSiN and Cr2O3 for AlCrN, generated at different temperatures of 700°, 800° and 900°C, respectively. From all of results, it is obvious that the AlCrN coating exhibited more excellent wear resistance and oxidation resistance than the uncoated end mill, TiN coating and TiAlSiN coating.

Decorative Ni-Cr plating on ferritic stainless steel was exposed to pure carbon dioxide (CO2) at 200 and 300oC for 180 hours under continuous and cyclic oxidation tests. After oxidation test, weight changes of samples exposed to CO2 were found to be less than that of samples exposed to air. However, weight changes were dependent on temperature and oxidation conditions. Heat-quench test was operated at temperature of 200-500oC for determining adhesion behavior of decorative Ni-Cr plating. From the heat-quench test, it revealed that adhesion ability between Ni-Cr plating layer and substrate increased with thickness of Ni pre-plating layer at temperature of 200 and 300°C. But, at temperature above 300°C, the adhesion ability increased with surface roughness of substrate before coating. In order to achieve important properties of decorative Ni-Cr plating, i.e., oxidation resistance, beautiful appearance and good adhesion, surface of substrate was necessarily prepared under medium roughness and then it was pre-plated with the thickest Ni layer before Cr coating was applied.

Although the phenomenon of hydrogen assisted cold cracking (HACC) and respective avoidance procedures have extensively been investigated in the seventies and eighties, the reasons for recent failures are still a lack of knowledge about the basic hydrogen effects on steel microstructures and, in particular, a lack of welding procedure specifications and standards accounting directly and consistently for cold cracking avoidance in modern high strength structural steels with yield strengths of up to 1 100 MPa. In previous several contributions the consequences of various heat treatment procedures targeted at HACC avoidance have been shown, as for instance their effects on stress-strain build up and on hydrogen diffusion in high strength steel welds. But, a principal interaction of three local influences on hydrogen assisted cold cracking, i.e. local microstructure; local mechanical load and local hydrogen content have not yet been studied in detail for these materials. For this, a numerical model for HACC has been developed, accounting particularly for crack-initiation and crack-propagation criteria, like the hydrogen redistribution during the process of cracking. The numerical model has been used to investigate HACC in such materials, i.e. in the weld microstructures of an S 1100 QL steel, under severe restraint and various hydrogen levels. The results were achieved by in depth thermal and structural finite element simulations combined with numerical hydrogen diffusion modelling. By such procedure, HACC in single-layer welded plates with thickness of 20.0 mm at realistic restraints has been studied. As a particular result, it turned out that the crack-initiation location is typically in the centre of the weld metal (WM), where only a single crack is initiated at hydrogen contents of up to 10.0 Nml/100 g Fe. But, it was evidently shown by such analyses that the crack-initiation location is shifted into the HAZ and that multiple cracking occurs at higher hydrogen contents of up to 15.0 Nml/100 g Fe.

Corrosion behavior of diamond-like carbon (DLC) films was evaluated via potentiodynamic polarization in a 3.5 wt. % NaCl solution with pH 2 at room temperature. The polarization results elucidated that the corrosion resistance of the films was enhanced with the variation of the chemical compositions and film thicknesses. The use of the spectromicroscopy method in the investigation of the pitting corrosion was a success in this study. Formation of orbital mapping, bonding state, and composition of the DLC films at non-corrosion and corrosion areas indicate the different structures between DLC and graphite oxide. Also, the π* (C=C) and π* (C=O) bonding states were found to increase in the corrosion areas. This finding not only exhibited the increase of sp2 content but also promoted the rise of oxygen atoms in corrosion zones. Consequently, the present results indicate that the synchrotron–based spectromicroscopy plays an important role in the characterization of the corrosion on DLC films.