ICMCTF2018 Session BP: Symposium B Poster Session

Aluminum alloys are light and have good workability; however, they have drawbacks such as low hardness and poor wear resistance. These drawbacks limit their wide application in the automotive field. The deposition of a diamond-like carbon (DLC) film, which has high hardness and good wear resistance, on the substrate surface can improve these drawbacks. Because aluminum alloys and DLC films have poor affinity, the adhesion between them is poor. However, the usage of an interlayer can improve the adhesion between them. In this study, to investigate the effect of multi-interlayers on the adhesion and durability, a DLC film with an interlayer of Ti, Si-DLC, or Ti/Si-DLC was deposited on the EN AW-2024 Al alloy substrate via plasma enhanced chemical vapor deposition. Argon bombardment treatment was conducted to clean the substrate surface before deposition, the Ti interlayer was deposited via sputtering for 15 min, the Si-DLC interlayer was deposited using gas mixture of tetramethylsilane and methane for 15 min, and DLC was deposited using methane gas for 90 min. The nano-hardness of the Ti/Si-DLC multi-interlayered sample reached 21 GPa, which is nearly 4 GPa more when compared with single interlayered samples. A ball-on-disc test showed that the wear volumes of the ball and the multi-interlayered sample were smaller compared with the single interlayered samples. In addition, the durability distance of the Ti/Si-DLC multi-interlayered sample was 3300 m, increasing more than 1500 m than the single interlayered samples.

The fatigue properties are very important for cutting tools due to service life. Due to improve fatigue properties of cutting tools, transition metal nitrides with soft metal (Cu, Ni etc.) are coated on cutting tool materials. To investigate Cu effect on fatigue properties of transition metal nitride coatings, TiZrNbN and Cu doped TiZrNbN coatings were deposited on M2 high speed steel using reactive closed field unbalanced magnetron sputtering (CFUBMS) in bias voltage of -80V, coating pressure of 0.26 Pa and Cu target current of 0.6 A. Microstructure properties of the coatings were determined by XRD, SEM and EDAX. Mechanical properties of the coatings were examined with microhardness test. Fatigue properties of the films were examined using multipass scratch tester. According to the results, the mechanical properties of TiZrNbN doped Cu is better than TiZrNbN.

Acknowledgements

In order to access this highly interesting material characteristics, physical vapour deposition (PVD) can be used to make this promising material system accessible to many other applications and extend the field of operation. However, the most common deposition temperatures of about 500 °C do not lead to the desired phase combination, but rather to homogeneous, X-ray amorphous thin films. Alloying titanium to the ternary system is known to stabilise the T₂ phase, by substituting the Mo atoms within the tetragonal crystal structure up to concentrations of 40 % - also reducing the density significantly.

1500 °C by using X-ray diffraction analysis as well as various (high-resolution) electron microscopy techniques and differential scanning calorimetry (DSC). The mechanical properties were investigated by nano-indentation of the as deposited and annealed state.

Titanium materials are widely used in aerospace, automotive and biomaterial engineering fields due to high specific strength, superior fatigue and corrosion resistance as well as excellent biocompatibility. However, titanium exhibits low hardness and poor wear resistance. Therefore, the development of a suitable surface modification technology is necessary to expand the use of titanium materials. In order to improve hardness and wear resistance of materials, there is the method to form the hard ceramics layer on the matrix surface. In this study, carburizing method was applied. The carburizing method can form the carbide layer which is superior in adhesion with the matrix compared with PVD or CVD method. However, in conventional carburizing methods, the deterioration of the mechanical properties of the matrix as a result of long-term and high-temperature processing is problematic. Therefore, spark plasma sintering technique, which features short processing times, was applied to form a carbide layer in this study. The purpose of this research is to form a TiC layer on commercially pure Ti (CP-Ti) and evaluate its properties. CP-Ti was used as the substrate, and graphite powder was used as the carburizing source. XRD analyses indicated that a TiC layer was formed on the substrates. Corrosion tests indicated that the corrosion resistance of the carburized samples was remarkably improved compared to that of CP-Ti. Wear tests revealed that the carburized samples exhibited low friction coefficients and improved tribological properties.

The present work evaluate the growth of the boride coatings formed in the surface AISI W2 steel by powder pack boriding. This process was carried out in the temperature range of 1173–1273 K with the exposure times ranging from 2 h to 8 h. The presence of borides Fe₂B formed on the surface of steel substrate was confirmed by optical microscopy and X-ray diffraction. The distribution of alloy elements from the surface to the interior was confirmed by energy dispersive X-ray spectroscopy.

The morphology presented the boride layer Fe₂B showed smooth and compact, with range thickness average from 9.96 ± 2.61 μm to 45.86 ± 4.13 μm. A mathematical model of the growth kinetics of the Fe₂B coatings on AISI W2 was proposed for the powder-pack boriding. The boron diffusion coefficient (D_Fe2B) was determinated by mass balance equation of the (Fe₂B/substrate) interface, the kinetic model was set for the Fe₂B coatings, assuming that the growth of boride layers follows a parabolic growth law. In addition, a contour diagram describing the evolution of Fe₂B coatings as a function of time and temperature parameters was proposed to be used in practical application. Finally, the boron activation energy for the AISI W2 steel is estimated as 183.44 kJ mol⁻¹ and this value of energy was compared with the literature data.

Integration of smooth nanocrystalline diamond coatings on steel substrates for biomedical implant applications has great application potentials due to their extraordinary wear/corrosion resistance and biocompatibility. However, CVD deposition of adherent and continuous diamond coating on steel substrates has met technical barrier of easy delamination. We will report on our recent progress on enhancing the adhesion of diamond coatings on steel substrates by using CrN/Al interlayer. The morphology, microstructure, composition and adhesion of the formed surface products are comprehensively characterized by SEM, TEM, XRD, Raman and synchrotron XAS as well as indention test. The fundamental mechanism of enhanced interfacial adhesion is discussed.

First principles calculations of undefected MoN/TaN superlattices suggest an interface-induced structural transformation from cubic to tetragonal phases (ζ-TaN, ζ-MoN). An analysis of their elastic constants reveals that the TaN volume fraction must be larger that that of MoN in order to be mechanically stable. This stability range can be further influenced by considering the point defects, namely vacancies. It is shown that the stability of superlattices critically depends not only on the amount of vacancies, but also on their distribution as well as on the superlattice bi-layer period. Impact of the interface and its orientation on the tensile strength is also briefly presented.

To compare the calculated results with experiments, magnetron-sputter deposited superlattices with various bi-layer periods are studied using conventional XRD, conventional and high-resolution TEM, and mechanical testing. The structural analysis confirms single-phase cubic superlattices with a strong (100), (110) or (111) interface orientation, as dictated by the MgO substrate orientation. Quantitative EELS measurements are used to prove the non-stoichiometry of individual constituents, MoN and TaN, as a function of the bi-layer period.

Experimental results reveal that the duplex treated fabrics can achieve water contact angle (WCA) over 118°. Anti-staining tests performed at 1, 4, and 10 weeks after surface treatment show that the the tested fabrics can tolerate 10 times of the washing test without altering surface appearance. Results of SEM and EDS analysis show that fluorocarbons still exhibit on the surfaces of PET fabrics after anti-staining tests. Above all, a spraying/plasma polymerization duplex coating on the surfaces of PET fabrics exhibits favorable hydrophobicity and anti-staining durability.

The focus is deformation mechanisms of transition metal nitride nano-composites coatings. The deformation in these materials is strongly dependent on interface structure and become more complex in nano-composites involving high density of interfaces. We present mechanical response of TiN/ZrAlN multilayers and monolithic ZrAlN nano-composite coatings investigated through nano indentation and micropillar compression tests. The study highlights effect of interface structure on pre yield and post yield behavior of nano scale multilayer deformation in compression.

To understand stress-strain response in a uniaxial micropillar compression tests the pillars of height of 1 mm and diameter of 300 nm were compressed using in situ SEM nanoindenter equipped with a flat punch (diameter 5mm)[Ref 2]. The pillars were milled using focused ion beam. The interface structure of the multilayers is tuned by varying growth parameters during magnetron sputter deposition on MgO (001) substrates. The growth temperatures above 700 °C facilitated in situ segregation of ZrN-and AlN- rich domains within ZrAlN layer during growth [Ref 1]. The growth conditions and multilayer design are varied to tailor crystal structure of AlN rich domains from cubic to wurtzite and consequently to obtain coherent, semicoherent, and incoherent interfaces. Dependence of plastic deformation and work hardening on the multilayer period as well as on the coherency of involved interfaces is investigated. Micropillar compression tests revealed higher yield stresses and larger post yield displacements in 2 and 5 nm thin ZrAlN layers consisting of cubic phases of ZrN and AlN- rich domains forming coherent interfaces. For 15 and 30 nm thick ZrAlN layers, involving incoherent interfaces, the dominant crack propagation occur through layer interfaces. The dominant deformation mechanisms in connection with interface coherency and multilayer periodicity will be presented.

Aluminum oxynitride (Al-O-N) in its transparent ceramic form provides attractive properties for hard coatings. Thin films of this material with different O and N contents were deposited by reactive unbalanced closed field direct current magnetron sputtering (R-UCFDCMS) and investigated with respect to the induced changes upon varying O/N ratios.

It was discovered that O addition leads to a gradual transformation of polycrystalline wurtzite AlN via Al-O-N nanocomposite towards amorphous Al₂O₃. The boundary between polycrystalline AlN and Al-O-N nanocomposite is set by the solubility limit of O in AlN and was found to be at 8 at% O. Below this critical value, O substitutes N in in the wurtzite lattice. This leads to a continuous unit cell shrinkage in c direction measurable by XRD. Above 8 at%, O starts to surround crystallites in the form of an amorphous Al₂O₃ matrix.

The shrinkage of the c lattice parameter upon O incorporation can hypothetically be attributed to the generation of Al vacancies. Since O has one valence electron more than the N it replaces, the ideal wurtzite 1:1 stoichiometry of electron donor and acceptor as found in AlN can no more be matched. In order to maintain the wurtzite crystal structure, the proportional amount of Al has to reduce to fit the stoichiometry AlO_1.5xN_1-x. The hypothesis that this is achieved through vacancies in the Al lattice positions was tested by ab initio DFT calculations. Lattice parameter changes upon O introduction and consequent Al vacancy defect generation were calculated and found to be in good agreement with the experimentally observed values. The obtained results were compared to data for the related ternary Al-Si-N system.

The potential use of chromium carbide thin films has been a great interest to academia and industry due to their outstanding properties such as chemical stability, low coefficient of friction, adequate hardness and high wear resistance. In this study, the chromium carbide thin films were fabricated by a magnetron sputtering using different power supply systems, including direct-current (DC), high power impulse magnetron sputtering (HiPIMS), and superimposed middle-frequency (MF)-HiPIMS. The Cr target poisoning status was controlled by a plasma emission monitoring system by adjusting the gas flow ratio of Ar and acetylene (C₂H₂ ). The morphology and microstructure of thin films were evaluated by scanning electron microscope. The crystallinity of films was studied using X-ray diffractometer. The electron probe micro analyzer, X-ray photoelectron spectroscope, and Raman spectroscope were used to determine the chemical compositions and binding structures of thin films. The mechanical, adhesion and tribological properties were explored by using scratch tester, tribometer, and nanoindentation. The influence of different power supply systems on the microstructure, chemical composition, and mechanical properties of chromium carbide films were investigated in this work.

Metal-containing carbon-based films (Me-C films) have been attracted much attention because metal-dopping can effectively improve and regulate film’s properties (such as reducing the internal stresses, enhancing the adhesion to the substrate and improving environmental sensitivity of tribology). It has been wildly reported that various metals have been introduced into carbon-based films by different groups. However, it will bring wide differences in precisely controlling microstructure and interaction mechanism etc. aspects to metallic dopping carbon-based films due to diverse metallic elemental, prepared methods and conditions.

This report highlights a peculiar phenomenon that spontaneous formation of various nanostructure in the carbon-based films during co-deposition of different metallic element process. Consideration of different interaction between metal and carbon, we choice copper, titanium, and nickel as three typically dopping metals. The influence of various metallic elements on self-organizing special nanostructure in carbon-metal films is systematically studied. For copper, it is noncarbide and immiscible with carbon, self-organized nano-multilayered structure can be formed in the copper-carbon film when the copper concentration maintaining at 20%-40% at.%; Titanium are strong carbide former, the nanocomposite structure of titanium carbide nanocrystalline dissolved in the amorphous carbon matrix is observed in the titanium-carbon film; Nickel possess the ability to catalysis the growth of carbon nanowires, and self-organized carbon nano-wires structure in nickel-carbon film has been successfully prepared, the field-emission tests of this self-assembled carbon nanowires structured film shows excellent behaviors.

ZrSiN-Ag thin films were deposited by reactive magnetron sputtering in order to study the effect of addiction of silver on the structure, chemical composition and mechanical properties in ZrSiN thin films. The structure of thin films was characterized by X-ray diffraction (XRD), the morphology by scanning electron microscopy (SEM) and the chemical composition by energy-dispersive x-ray spectroscopy (EDS). A nanoindenter was used to study the mechanical properties such as hardness and elastic module in function the silver content in the films deposited. The XRD results showed that nanostructured ZrSiN-Ag thin films were obtained. The ZrN film exhibited a face-centered cubic (f.c.c) phase with columnar structure while that the Zr-Si-N films showed a mixture of f.c.c and near-amorphous phases without columnar structure, similar to the ZrSiN-Ag films. The hardness obtained for ZrN film was of 58,80 GPa, which decreases as silver contents increase.

Aluminum silicon nitride (AlSiN) thin films with different Si content were deposited using the simultaneous laser ablation of aluminum and silicon targets in a nitrogen atmosphere and a substrate temperature of 200 ^oC. Films were deposited at two values of working pressure, 0.6 and 1 Pa. The silicon content in the films ranged between 3 and 20 at. %, and was varied by changing the density of the plasma produced during the ablation of the silicon target, i.e. the highest the plasma density gave the highest the silicon concentration in the films. The plasma parameters (mean kinetic ion energy and plasma density) were measured using a planar Langmuir probe. Samples deposited with low silicon contents (up to about 6 at. %), contained nanocrystals embedded in an amorphous matrix. Those crystals were identified as hexagonal aluminum nitride (w-AlN). For higher concentrations of silicon the amorphous phase was predominant and the nanocrystals were no longer observed. The hardness of the films had a maximum value of 30 Gpa, and an elastic recovery of about 50 % when the silicon content was close to 4 at. %. For higher silicon concentrations the hardness was lower at 19 GPa. Scratch tests were carried out on samples with different silicon contents. For the samples with low silicon contents (the highest hardness) delamination was observed at loads of 90 N, in the transition to the solid solution regime (Si content of 8 at. %) delamination was observed to begin at 10 N, and for the highest concentrations of silicon no delamination of the films was observed even for loads of 90 N.

In order to deposit DLC to the inner surface of a small hole 0.1 mm in diameter and 5 mm in depth, PECVD employing MVP is conducted with blowing source gas from nozzle to the hole inlet. After DLC coating, film thickness is measured by 0.1 mm in axial direction of the hole and the maximum depth where a film thickness is detectable is defined as coating depth. We found that blowing source gases increases coating depth. Furthermore, the linear increase of coating depth from 0 to 1 mm was observed with the increase of the flow rate of blown gas from 0 to 780 sccm. We are going to further investigate the effect of source gas flux on coating depth by numerical simulation of plasma with the commercial software VizGlow at the conference.

References

[1] R. Ota, H. Kousaka, L L. Raja, N. Umehara, M. Murashima: Internal DLC Coating to Small Hole in a Diameter of 100 μm by Plasma Enhanced Chemical Vapor Deposition with Gas Blowing to the Hole, ICMDT 2017, (2017).

Quaternary AlCrSiN coatings with silicon content ranging from 0 to 21 at.% were deposited on WC-Co alloy substrates by an arc ion plating technique using Cr-Al and Cr-Si composite targets in an N2/(Ar+N2) gas m ixture for hard material processing milling tools. The microstructure, mechanical, wear, tribological properties of the coatings were investigated by XRD, XPS, FESEM, HRTEM, surface 3D profiler, nano-indentation, scratch tester, and ball-on-disc tribo-meter. As the silicon content increased, the microstructure of the coatings changed from columnar grains to interconnected fine grains, and finally to nanocomposite structure, in which (Al,Cr)N nanocrystallites were surrounded by an amorphous silicon nitride matrix. The incorporation of silicon results in the (Al,Cr)N crystallite size refinement and the decrease of the average surface roughness. The nanohardness of the AlCrSiN coatings showed higher hardness values than that of AlCrN coating. The strengthening mechanisms include solid solution hardening and grain boundaries strengthening through the formation of a thin amorphous layer. Moreover, it was found that the improved nanohardness and the H/E ratio contributed to excellent wear resistance of the coatings. The friction coefficient and wear rate of the AlCrSiN coatings first decreased and then increased with increasing silicon content. The friction coefficient and wear rate were also mainly related to the lubricant wear debris in this work.

Functional graded Ti–Al–Si–N–O nanocomposite coatings were deposited onto WC-Co substrates by a filtered arc ion plating system using TiAl₃ and Ti₄Si composite targets under N2 atmosphere. XRD and XPS analyses revealed that the synthesized Ti–Al–Si–N–O coatings were nanocomposite consisting of nanosized (Ti,Al,Si)N crystallites embedded in an amorphous Si₃N₄/SiO₂ matrix. The hardness of the Ti–Al–Si–N–O coatings exhibited the maximum hardness values of ∼43GPa at a Si content of ~5.63 at.% due to the microstructural change to a nanocomposite as well as the solid-solution hardening. Ti–Al–Si–N–O coating with Si content of around 5.63 at.% also showed perfect adhesive strength value of 105.3N. These excellent mechanical properties of Ti–Al–Si–N–O coatings could help to improve the performance of machining tools and cutting tools with application of the coatings. Ti-Al-Si-N-O coatings were applied to insert tools. Their performances were evaluated about cutting-time and cutting-length to Inconel 718 super alloys. Performance of the coated tools were evaluated and compared with different Ti-Al-Si-N-O coatings onto cemented carbide substrates. Especially, the Ti-Al-Si(5.63at%)-N coated tool showed better performance and best tool life in this work.

Photocatalysis is a promising method for decontamination of air, water and soil. In particular, photocatalytic purification of wastewater is becoming an increasingly popular process, with the wide range of titanium dioxide-based materials successfully applied as photocatalysts for water treatment application. However, the use of titanium dioxide for efficient water treatment application is restricted with two major limiting factors, namely a relatively high band gap value and low photonic efficiency. The high band gap value results in titania photocatalysts being activated only with ultraviolet (UV) irradiation (<5% of the solar spectrum), therefore, for practical use, additional irradiation sources are required. Consequently, it is rather difficult to achieve high reaction rates, as required when dealing with heavily-polluted industrial wastewater or high throughput systems. As photocatalytic wastewater treatment is aimed at being an economical and practical technique, it is desirable to avoid the extra costs of using artificial light sources in the photocatalytic treatment setup. Use of natural sunlight represents a cheap and sustainable irradiation source, however, as in the case of titania-based photocatalysts, its efficiency can be rather low. Therefore, there is an obvious need for the development of photocatalytic materials based on the use of low band gap semiconductors, combining visible light activity with high photonic efficiency and high surface area.