Deposition of TiSiN coatings by arc ion plating process

Titanium silicon nitride (TiSiN) thin films were deposited on tungsten cemented carbide tools by cathode arc ion plating (AIP) process using alloy TiSi targets. The effects of silicon addition and negative substrate bias on the development of the textures of films were studied systematically by varying the bias voltage from −20 to −200 V. The structural features of the films were investigated in detail using X-ray diffraction. The effect of the texture on such mechanical properties as hardness and adhesion of the films was also studied. A maximum hardness of 42 GPa was obtained at a DC substrate bias of −150 V. The characteristics of TiSiN thin films exhibited excellent adhesion of over 150 N. The cutting performance of end-mills and drillers was evaluated by milling and drilling of highly hardened material under high-speed cutting conditions. The results reveal that cutting tools with TiSiN coatings markedly outperformed those with TiN coatings, and the uncoated cutting tools. TiSiN coating increased the cutting lifetime to seven times that of the uncoated one.     

Mechanical and electrochemical characterization of vanadium nitride (VN) thin films

Vanadium nitride (V-N) thin films were grown using a reactive d.c. magnetron sputtering process, from a vanadium target (99.999%) in an Ar/N₂ gas mixture at different deposition bias voltage. Films were deposited onto silicon (1 0 0) and RUS-3 steel substrates at 400 °C. Structural, compositional, mechanical and electrochemical characterizations were performed by X-ray diffraction (XRD), elastic forward analysis (EFA), nanoindentation, electrochemical impedance spectroscopy (EIS), and Tafel polarization curves, respectively. X-ray diffraction patterns show the presence of (1 1 1) and (2 0 0) crystallographic orientations associated to the V-N cubic phase. Nanoindentation measurements revealed that when the bias voltage increases from 0 V to −150 V the hardness and elastic modulus are increased from 11 GPa to 20 GPa and from 187 GPa to 221 GPa, respectively. EIS and Tafel curves showed that the corrosion rate of steel, coated with V-N single layer films deposited without bias voltage, diminishes 90% compared to the steel without this coating. On the other hand, when the V-N coating was deposited at the highest d.c. bias voltage (−150 V), the corrosion rate was greater than in the steel coated with zero-voltage (0 V) V-N films. This last result could be attributed to the formation of porosities produced by the ion bombardment during the deposition process.     

The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to −200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp³ carbon content and mechanical properties of the deposited DLC films. A maximum sp³ content of 33.3% was obtained at −100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.     

Ti-Cu-N hard nanocomposite films prepared by pulse biased arc ion plating

In this work, Ti-Cu-N hard nanocomposite films were deposited on high-speed-steel (HSS) substrates using a TiCu (88:12 at.%) single multi-component target by pulse biased arc ion plating. The influence of pulse bias voltages was examined with regard to elemental composition, structure, morphology and mechanical properties of the films. The Cu atomic content of Ti-Cu-N films was determined by Electron Probe Micro-Analyzer (EPMA). The structure and morphology were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Hardness and film/substrate adhesion were determined by nanoindenter and scratch test, respectively. The results showed that the content of Cu appeared to be in the range of 1.75-4.5 at.%, depending on pulse bias voltages. The films exhibit a preferred orientation TiN (1 1 1) texture when the substrate bias voltages were −100 V and −300 V, while the preferred orientation change to be a preferred orientation TiN (2 2 0) one when the substrate bias voltages increase to −600 V and −900 V. And no obvious sign of metal copper phase was observed. The SEM morphologies showed some macroparticles (MPs) on the surface of the films and the relative content of the MPs decreased significantly when the substrate bias voltages increased from −100 to −900 V. The maximum value (74 N) of the film/substrate adhesion of the films was obtained when the substrate bias voltage was −600 V with Cu content of 1.75 at.%. Hardness enhancement was observed, the value of the hardness increased firstly and reached a maximum value of 31.5 GPa, corresponding to Cu content of 1.75 at.%, and then it decreased when the substrate bias voltage changed from −100 to −900 V. The hardness enhancement was discussed related to the concept for the design of hard materials.     

RF-PACVD of water repellent and protective HMDSO coatings on bell metal surfaces: Correlation between discharge parameters and film properties

Hexamethyldisiloxane (HMDSO) films have been deposited on bell metal using radiofrequency plasma assisted chemical vapor deposition (RF-PACVD) technique. The protective performances of the HMDSO films and their water repellency have been investigated as a function of DC self-bias voltage on the substrates during deposition. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. Optical emission spectroscopy (OES) analyses of the plasma during deposition reveal no significant change in the plasma composition within the DC self-bias voltage range of −40 V to −160 V that is used. Raman and X-ray photoelectron spectroscopy (XPS) studies are carried out for film chemistry analysis and indicate that the impinging ion energy on the substrates influences the physio-chemical properties of the HMDSO films. At critical ion energy of 113 qV (corresponding to DC self-bias voltage of −100 V), the deposited HMDSO film exhibits least defective Si-O-Si chemical structure and highest inorganic character and this contributes to its best corrosion resistance behavior. The hardness and elastic modulus of the films are found to be bias dependent and are 1.27 GPa and 5.36 GPa for films deposited at −100 V. The critical load for delamination is also bias dependent and is 11 mN for this film. The water repellency of the HMDSO films is observed to be dependent on the variation in surface roughness. The results of the investigations suggest that HMDSO films deposited by RF-PACVD can be used as protective coatings on bell metal surfaces.     

Structure and properties of DLC–MoS2 thin films synthesized by BTIBD method

Diamond-like carbon (DLC)–MoS₂ composite thin films were synthesized using a biased target ion beam deposition (BTIBD) technique in which MoS₂ was produced by sputtering a MoS₂ target using Ar ion beams while DLC was deposited by ion beam deposition with CH₄ gas as carbon source. The structure and properties of the synthesized films were characterized by X-ray diffraction, X-ray absorption near edge structure (XANES), Raman spectroscopy, nanoindentation, ball-on-disk testing, and corrosion testing. The effect of MoS₂ target bias voltage, ranging from −200 to −800 V, on the structure and properties of the DLC–MoS₂ films was further investigated. The results showed that the hardness decreases from 9.1 GPa to 7 GPa, the Young?s modulus decreases from 100 GPa to 78 GPa, the coefficient of friction (COF) increases from 0.02 to 0.17, and the specific wear rate coefficient (k) increases from 5×10⁻⁷ to 5×10⁻⁶ mm³ N⁻¹ m⁻¹, with increasing the biasing voltage from 200 V to 800 V. Also, the corrosion resistance of the DLC–MoS₂ films decreased with the raise of biasing voltage. Comparing with the pure DLC and pure MoS₂ films, the DLC–MoS₂ films deposited at low biasing voltages showed better tribological properties including lower COF and k in ambient air environment.     

Effects of pulsed bias duty ratio on microstructure and mechanical properties of TiN/TiAlN multilayer coatings

TiN/TiAlN multilayer coatings were deposited on M2 high speed steel by a pulsed bias arc ion plating system. The effect of pulsed bias duty ratio on the microstructure, mechanical and wear properties was investigated. The amount of macroparticles reduced with the increase of the duty ratio. The surface roughness was 0.0858 μm at duty ratio of 50%. TiN/TiAlN multilayer coatings were crystallized with orientations in the (1 1 1), (2 0 0) (2 2 2) and (3 1 1) crystallographic planes and the microstructure strengthened at (1 1 1) preferred orientation. At duty ratio of 20%, the hardness of TiN/TiAlN multilayer coatings reached a maximum of 3004 HV, which was 3.2 times that of the substrate. The adhesion strength reached a maximum of 77 N at 50% duty ratio. Friction and wear analyses were carried out by pin-on-disc tester at room temperature. Compared with the substrate, all the specimens coated with TiN/TiAlN multilayer coatings exhibited better tribological properties.     

A magnetron sputtering technique to prepare a-C:H films: Effect of substrate bias

Amorphous hydrogenated carbon (a-C:H) films were deposited by magnetron sputtering with a mixture gas of Ar and CH₄. The a-C:H films deposited by this method have relatively low internal stress (<1 GPa) compared to some films deposited by conventional deposition process. The effects of substrate bias voltage on microstructure, surface morphology and mechanical properties of the films were investigated by various techniques. It has been found that the polymer-like structure is dominated at low bias voltage (−100 V), while the diamond-like structure with the highest hardness and internal stress is the main feature of the a-C:H films deposited under high bias voltage (−300 V). With increasing the bias voltage further, the feature of diamond-like structure decreases associating with the increase of graphitization. The frictional test shows that the friction coefficient and wear rate of the a-C:H films are depended strongly on structure and mechanical properties, which were ultimately influenced by the deposition method and bias voltage.     

TiAlN coatings synthesised using a dense plasma focus system and varied focus shots

TiAlN coatings were synthesised by a 2.3 kJ pulsed plasma focus system. The effect of focus shots on crystallography, microstructure, surface morphology, roughness and hardness was investigated. The coating's crystallography and microstructure were investigated using X-ray diffraction (XRD) characterisation. The XRD data showed that TiAlN coatings were crystallised in the cubic NaCl B1 structure with orientations in the (111), (200), (220) and (311) crystallographic planes. Texture coefficients showed a competition between (111) and (200) planes. The coatings surface morphology and thickness analyses were carried out using scanning electron microscopy (SEM). SEM micrographs showed dense and uniformly spread film with fine-grained morphology with hardly any pit, hole and crater. The surface roughness and hardness of TiAlN coatings were investigated by atomic force microscopy and Vickers microhardness tester. Grain size and roughness were found to decrease, whereas thickness and hardness were found to increase, with increasing focus shots.     

The effect of substrate bias voltages on impact resistance of CrAlN coatings deposited by modified ion beam enhanced magnetron sputtering

CrAlN coatings were deposited on silicon and AISI H13 steel substrates using a modified ion beam enhanced magnetron sputtering system. The effect of substrate negative bias voltages on the impact property of the CrAlN coatings was studied. The X-ray diffraction (XRD) data show that all CrAlN coatings were crystallized in the cubic NaCl B1 structure, with the (1 1 1), (2 0 0) (2 2 0) and (2 2 2) diffraction peaks observed. Two-dimensional surface morphologies of CrAlN coatings were investigated by atomic force microscope (AFM). The results show that with increasing substrate bias voltage the coatings became more compact and denser, and the microhardness and fracture toughness of the coatings increased correspondingly. In the dynamic impact resistance tests, the CrAlN coatings displayed better impact resistance with the increase of bias voltage, due to the reduced emergence and propagation of the cracks in coatings with a very dense structure and the increase of hardness and fracture toughness in coatings.     

Ti/TiN multilayer thin films deposited by pulse biased arc ion plating

In this work, the effect of modulation period (Λ) on Ti/TiN multilayer films deposited on high-speed-steel (HSS) substrates using pulse biased arc ion plating is reported. The crystallography structures and cross-sectional morphology of Ti/TiN multilayer films were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. Their mechanical properties were determined via nanoindentation measurements, while the film/substrate adhesion via the scratch test. It was found that the highest hardness value reached 43 GPa for the modulation period of 54 nm, while the film/substrate adhesion also reached the highest value of 83 N. Furthermore, the hardness enhancement mechanism in the multilayer films is discussed.     

Structural and tribological properties of nitrogen doped amorphous carbon thin films synthesized by CFUBM sputtering method for protective coatings

Nitrogen doped amorphous carbon (a-C:N) films are a material that may successfully compete with DLC coatings, which have high hardness, high wear resistance, and a low friction coefficient. The a-C:N films were prepared on silicon substrate by a closed-field unbalanced magnetron sputtering method with a graphite target and using the Ar/N₂ mixture gases. And, we investigated the effects of various DC bias voltages from 0 to −300 V on the structural and tribological properties of the a-C:N films. This study was focused on improving physical properties of the a-C:N film by controlling process parameters like negative substrate DC bias voltage. The maximum hardness of the a-C:N film was 23 GPa, the friction coefficient was 0.08, and the critical load was 25 N on a Si wafer. Consequently, the structural and tribological properties of the a-C:N film showed a clear dependence on the energy of ions bombardment and the density of the sputtering and the reaction gases during film growth.     

Improvement of mechanical and tribological properties in steel surfaces by using titanium-aluminum/titanium-aluminum nitride multilayered system

Improvement of mechanical and tribological properties on AISI D3 steel surfaces coated with [Ti-Al/Ti-Al-N]_n multilayer systems deposited in various bilayer periods (Λ) via magnetron co-sputtering pulsed d.c. method, from a metallic binary target; has been studied in this work exhaustively. The multilayer coatings were characterized in terms of structural, chemical, morphological, mechanical and tribological properties by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy, nanoindentation, pin-on-disc and scratch tests, respectively. The failure mode mechanisms were studied by optical microscopy. Results from X-ray diffraction analysis revealed that the crystal structure of TiAl/TiAlN multilayer coatings has a tetragonal and FCC NaCl-type lattice structures for Ti-Al and Ti-Al-N, respectively, i.e., it was found to be non-isostructural multilayers. An enhancement of both hardness and elastic modulus up to 29 GPa and 260 GPa, respectively, was observed as the bilayer periods (Λ) in the coatings were decreased. The sample with a bilayer period (Λ) of 25 nm and bilayer number n = 100 showed the lowest friction coefficient (∼0.28) and the highest critical load (45 N), corresponding to 2.7 and 1.5 times better than those values for the coating deposited with n = 1, respectively. These results indicate an enhancement of mechanical, tribological and adhesion properties, comparing to the [Ti-Al/Ti-Al-N]_n multilayer systems with 1 bilayer at 26%, 63% and 33%, respectively. This enhancement in hardness and toughness for multilayer coatings could be attributed to the different mechanisms for layer formation with nanometric thickness such as the novel Ti-Al/Ti-Al-N effect and the number of interfaces that act as obstacles for the crack deflection and dissipation of crack energy.     

High-temperature oxidation resistant (Cr, Al)N films synthesized using pulsed bias arc ion plating

(Cr, Al)N films were deposited by pulsed bias arc ion plating on HSS and 316L stainless steel substrates. With pulsed substrate bias ranging from −100 V to −500 V, the effect of pulsed bias on film composition, phase structure, deposition rate and mechanical properties was investigated by EDX, XRD, SEM, nanoindentation and scratch measurements. The high-temperature (up to 900 °C) oxidation resistance of the films was also evaluated. The results show that Al contents and deposition rates decrease with increasing pulsed bias and the ratio of (Cr + Al)/N is almost constant at 0.95. The as-deposited (Cr, Al)N films crystallize in the pseudo-binary (Cr, Al)N and Al phases. The film hardness increases with increasing bias and reaches the maximum 21.5 GPa at −500 V. The films deposited at −500 V exhibit a high adhesion force, about 70 N, and more interestingly good oxidation resistance when annealed in air at 900 °C for 10 h.     

Microstructures and tribological properties of CrN/ZrN nanoscale multilayer coatings

Nanoscale multilayer CrN/ZrN coatings with bilayer thicknesses ranging from 11.7 to 66.7 nm were prepared by reactive magnetron sputtering techniques. The structure of the thin films was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction results showed that CrN individual layers presented a <1 1 1> preferred orientation in the multilayer coatings. The diffraction peaks of CrN shifted continuously to low diffraction angle with decreasing bilayer thickness. TEM observations showed that the multilayer did not form a superlattice structure instead of the coexistence of nanocrystalline CrN and ZrN layers. Columnar growth for all the coatings was observed by cross-sectional SEM. Nanoindentation tests showed that the multilayer coatings had almost a constant nanohardness of 29 GPa in spite of the variations of bilayer thickness. Pin-on-disk tests indicated that both the friction coefficients and wear rates increased when decreasing bilayer thickness. However, in comparison with the monolayer coating, the multilayer coatings exhibited excellent wear resistance.     

Effect of deposition and annealing temperature on mechanical properties of TaN film

Tantalum nitride films (TaN) were synthesized by microwave ECR-DC sputtering. The effects of deposition and annealing temperature on mechanical properties of TaN films were investigated. Cross-section pattern, microstructure and binding energy of the films were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Mechanical properties were evaluated using nano-indentation and scratch tester. The results showed that the maximal hardness value of approximately 40 GPa was deposited in the TaN sample at 573 K. While the preparation temperature decreased, the hardness, modulus and adhesion of TaN film also decreased. Hardness and modulus also decreased with the increase in annealing temperature. Meanwhile the adhesion strength was also sensitive to the annealing temperature, with a maximum adhesion strength of 40 N measured in the TaN film annealed at 448 K. The results demonstrated that a desirable mechanical property of TaN films deposited by DC reactive magnetron sputtering can be obtained by controlling the deposition and annealing temperature.     

TiCN/TiNbCN multilayer coatings with enhanced mechanical properties

Enhancement of mechanical properties by using a TiCN/TiNbCN multilayered system with different bilayer periods (Λ) and bilayer numbers (n) via magnetron sputtering technique was studied in this work. The coatings were characterized in terms of structural, chemical, morphological and mechanical properties by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. Results of the X-ray analysis showed reflections associated to FCC (1 1 1) crystal structure for TiCN/TiNbCN films. AFM analysis revealed a reduction of grain size and roughness when the bilayer number is increased and the bilayer period is decreased. Finally, enhancement of mechanical properties was determined via nanoindentation measurements. The best behavior was obtained when the bilayer period (Λ) was 15 nm (n = 200), yielding the highest hardness (42 GPa) and elastic modulus (408 GPa). The values for the hardness and elastic modulus are 1.6 and 1.3 times greater than the coating with n = 1, respectively. The enhancement effects in multilayer coatings could be attributed to different mechanisms for layer formation with nanometric thickness due to the Hall-Petch effect; because this effect, originally used to explain the increase in hardness with decreasing grain size in bulk polycrystalline metals, has also been used to explain hardness enhancements in multilayers taking into account the thickness reduction at individual single layers that make the multilayered system. The Hall-Petch model based on dislocation motion within layers and across layer interfaces, has been successfully applied to multilayers to explain this hardness enhancement.     

Microstructure and mechanical properties of CrN films fabricated by high power pulsed magnetron discharge plasma immersion ion implantation and deposition

CrN films with strong adhesion with the substrate have been fabricated on Ti6Al4V alloy using novel plasma immersion ion implantation and deposition (PIII&D) based on high power pulsed magnetron sputtering (HPPMS). A macro-particle free chromium plasma is generated by HPPMS while the samples are subjected to high voltage pulses to conduct PIII&D. The CrN coatings have a dense columnar structure and low surface roughness. The grains in the films have the face-center cubic (fcc) structure with the (2 0 0) preferred orientation. An excellent adhesion is achieved with a critical load up to 74.7 N. An implantation voltage of 18 kV yields a hardness of 18 GPa and better wear resistance and a low friction coefficient of 0.48 are achieved.     

Chemical composition of ZrC thin films grown by pulsed laser deposition

ZrC films were grown on (1 0 0) Si substrates by the pulsed laser deposition (PLD) technique using a KrF excimer laser working at 40 Hz. The nominal substrate temperature during depositions was set at 300 °C and the cooling rate was 5 °C/min. X-ray diffraction investigations showed that films deposited under residual vacuum or under 2 × 10⁻³ Pa of CH₄ atmosphere were crystalline, exhibiting a (2 0 0)-axis texture, while those deposited under 2 × 10⁻² Pa of CH₄ atmosphere were found to be equiaxed and with smaller grain size. The surface elemental composition of as-deposited films, analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), showed the usual high oxygen contamination of carbides. Once the topmost 2-4 nm region was removed, the oxygen concentration rapidly decreased, down to around 3-8% only in bulk. Simulations of the X-ray reflectivity (XRR) curves indicated a smooth surface morphology, with roughness values below 1 nm (rms) and films density values of around 6.30-6.45 g/cm³, very close to the bulk density. The growth rate, estimated from thickness measurements by XRR was around 8.25 nm/min. Nanoindentation results showed for the best quality ZrC films a hardness of 27.6 GPa and a reduced modulus of 228 GPa.     

Influence of annealing temperature on the structural, optical and mechanical properties of ALD-derived ZnO thin films

ZnO thin films grown on Si(1 1 1) substrates by using atomic layer deposition (ALD) were annealed at the temperatures ranging from 300 to 500 °C. The X-ray diffraction (XRD) results show that the annealed ZnO thin films are highly (0 0 2)-oriented, indicating a well ordered microstructure. The film surface examined by the atomic force microscopy (AFM), however, indicated that the roughness increases with increasing annealing temperature. The photoluminescence (PL) spectrum showed that the intensity of UV emission was strongest for films annealed at 500 °C. The mechanical properties of the resultant ZnO thin films investigated by nanoindentation reveal that the hardness decreases from 9.2 GPa to 7.2 GPa for films annealed at 300 °C and 500 °C, respectively. On the other hand, the Young's modulus for the former is 168.6 GPa as compared to a value of 139.5 GPa for the latter. Moreover, the relationship between the hardness and film grain size appear to follow closely with the Hall-Petch equation.