Si3N4和52100钢对磨副材料对CrN薄膜干摩擦学行为的影响

利用阴极电弧离子镀技术在316L不锈钢基体上制备了CrN薄膜。采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、纳米压痕仪对CrN薄膜的形貌、成分和力学性能进行了表征。为了研究Si_3N_4和52100钢对磨副材料对CrN薄膜和316L不锈钢干摩擦行为的影响,在2N、5N、8N三种载荷下,将CrN薄膜和316L不锈钢基体与Si_3N_4陶瓷球和52100钢球分别进行了往复式滑动干摩擦实验。采用扫描电子显微镜观察了磨痕的微观形貌,并对CrN薄膜和316L不锈钢基体的磨损机制进行了分析。结果表明:CrN薄膜表面平整,缺陷较少;CrN薄膜的纳米硬度约为28GPa,弹性模量约为350GPa;与Si_3N_4陶瓷球相比,CrN薄膜与52100钢球摩擦时摩擦因数相对较小(保持在0.7左右)且更加稳定;316L不锈钢的摩擦因数远大于CrN薄膜且波动较大;对磨球为Si_3N_4陶瓷球时,CrN薄膜的主要磨损机制为磨粒磨损,伴有少量的氧化和黏着磨损,316L不锈钢的磨损机制主要为磨粒磨损和塑性变形,伴有少量的氧化和黏着磨损;对磨球为52100钢球时,CrN薄膜的主要磨损机制为黏着磨损,伴有少量的氧化,316L不锈钢的磨损机制主要为黏着磨损,伴有少量的氧化和磨粒磨损。CrN薄膜与两种对磨球的磨损量均小于316L不锈钢基体的磨损量,说明CrN薄膜有效提高了基体的耐磨性。     

Stress tuning in AIN thin films

Aluminium nitride films were deposited on fused silica by reactive dc magnetron sputtering from an Al-target in an Ar/N₂ atmosphere. In-situ measurements during deposition provided data concerning mechanical stresses inherent to the growing thin films. By variation of both the gas composition (Ar, N₂) and the total gas flow in the vacuum chamber, the occuring intrinsic stresses could be shifted in magnitude and direction. Stress values of the AIN films ranged from ?0.9 GPa (compressive) to +1.2 GPa (tensile) when the Ar/N₂ ratio was varied between 3:1 and 1:3 for the different total gas flows of 50 sccm, 100 sccm, and 200 sccm (corresponding to total gas pressures of approximately 2 × 10^?1 Pa, 4 × 10^?1 Pa, and 8 × 10^?1 Pa respectively). Investigations of optical and structural film properties were carried out and the results were related to the observed film stress.     

Microstructure of brazed joints between mechanically metallized Si<Subscript>3</Subscript>N<Subscript>4</Subscript> and stainless steel

Brazing has been increasingly used to join metals to advanced ceramics. Brazing covalent materials requires either the use of active filler alloys or the previous metallization of the surface. To that end, a new and simple mechanical technique has been applied to metallize advanced ceramics, thus avoiding the use of costly Ti-based active filler alloys. The mechanical metallization of Si₃N₄ with Ti was employed as an alternative route to deposit active metallic films prior to brazing with stainless steel using 72% Ag--28% Cu or 82% Au—18% Ni eutectic alloys. The brazing temperatures were set to 40°C or 75°C above the eutectic temperature of each filler alloy. Ti-films of average thickness 4 μm produced adequate spreading of both filler alloys onto Si₃N₄ substrates, which were subsequently brazed to stainless steel. The interface of Si₃N₄/310 stainless steel basically consisted of a reaction layer, a precipitation zone and an eutectic microconstituent. Mechanically sound and vacuum-tight joints were obtained, especially upon brazing at relatively lower temperatures. Increasing the brazing temperature resulted in thermal cracking of the Si₃N₄, possibly due to increased thermal stress.     

Reactive pulse magnetron sputtered SiOxNy coatings on polymers

Amorphous SiO₂, Si₃N₄ and SiO_xN_y single layers have been deposited on silicon, glass and glycol modified polyethylene terephthalate substrates by reactive pulse magnetron sputtering. Apart from the expected correlation between refractive index, coating density and nitrogen content in the reactive gas mixture further results have been found regarding mechanical stress and the humidity barrier property of these thin films. The lowest compressive stress was observed in the coatings deposited with nitrogen contents of around 30% to 50% in the reactive gas mixture. The humidity barrier effect of the thin films already begins to increase significantly at low nitrogen contents of below 20% in the reactive gas. Additional investigations regarding chemical composition, coating adhesion and environmental stability complement this work with the main focus on optimizing these materials for optical multilayer systems on polymer substrates.     

Synthesis of aluminum nitride thin films by filtered arc ion plating deposition

Thin films of aluminum nitride (AlN) were deposited on stainless steel and glass substrates by a modified deposition technique, filtered arc ion plating, at an enhanced deposition rate. X-ray diffraction spectra confirmed the exclusive presence of AlN hexagonal wurtzite phase. Under a mixed gas (Ar + N₂) pressure of 0.90 Pa and a bias voltage of − 400 V, the deposited films exhibited a fairly low surface roughness of 2.23 nm. The thin films were proved higher than 75% transparent in the visible spectral region. The bonding strength between the film and substrate was verified higher than 20 N. Thus high performance of such AlN thin films can be expected in applications.     

Influence of bias voltages on the structure and wear properties of TiSiN coating synthesized by cathodic arc plasma evaporation

Nanocomposite TiSiN films have been deposited on M2 tool steel substrates using TiSi alloy as target by a dual cathodic arc plasma deposition (CAPD) system. The influences of bias voltages on the microstructure, mechanical and tribological properties of the films were investigated. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction techniques were employed to analyse the microstructure, grain size and residual stress. Nano-indentation and tribometer testers were used to measure the mechanical and tribological properties of nanocomposite TiSiN thin films. The results showed that the hardness of the films ranged from 25 to 37 GPa, which were higher than that of TiN (21 GPa). The coefficient of friction of the TiSiN thin films was more stable but was higher than that of TiN when wear against both Cr steel and WC-Co ball, respectively. When encountered with both Cr steel and WC-Co ball of the counter ball, the tribological mechanisms of TiSiN thin films are adhesive and abrasion wears, respectively. It has been found that the microstructure, mechanical and wear properties of the films were correlated to bias voltage, grain size, and amorphous Si₃N₄ nanocomposite formed in film structure, resulting in a superhard TiSiN coating.     

Residual compressive stress in sputter-deposited TiC films on steel substrates

Polycrystalline TiC films with thickness between 0.1 and 2.8 microm were deposited by r.f. sputtering onto 1010 steel and borosilicate glass substrates at 200°C. All films were found to be in a state of compression. For a film grown under a given set of deposition conditions, the incremental compressive stress, i.e. the average stress in the uppermost deposited layer, was generally found to be largest near the film-substrate interface and to become constant with film thickness t_f for t_f ? 0.3 microm. However, for a given t_f the incremental stress increased with a decrease in the argon sputtering pressure P_Ar. Experimental results showed that the incremental compressive stress in bulk films could be directly related to the trapped argon concentration. Argon incorporation is due to the burial of energetic species incident on the growing film surface from two primary sources: energetic neutrals produced by Ar⁺ ions scattered off the target in binary collisions and Ar⁺ ions accelerated to the substrate owing to its induced negative potential with respect to the positive space charge region in the r.f. discharge. The trapped argon concentration from both contributions increased with decreasing P_Ar. All films grown on steel substrates exhibited good adhesion as indicated by indentation and diamond stylus scratch tests. The residual compressive stress in the films was found to be beneficial for wear-related applications in which the film was subjected to a large tensile stress.     

AES study of passive films formed on a type 316 austenitic stainless-steels in a stress field

The type AISI 316 stainless steel, in addition to the principal alloying elements chromium and nickel, contains 2.5–3.5% of molybdenum. This element is added to improve the mechanical properties and the pitting resistance of austenitic alloys. Concerning the Stress Corrosion Cracking (SCC) resistance of austenitic stainless steels, molybdenum additions to alloys have a variable effect: the effect is detrimental for small additions of Mo, and it is beneficial for the alloy containing more than 4% Mo. Thus the Mo concentration on passive film plays an important role on the SCC resistance of steels. On the other hand, in a previous investigation, it was shown that the composition of passive films formed on the stressed 302 alloy depended on the compressive or tensile nature of stresses. Consequently, the aim of the present work is to study the composition of passive films formed on 316 steel and the migration of molybdenum in a stress field. Thus, Auger electron spectroscopy spectra were recorded to determine the chemical composition of the passive films formed on both sides of the type AISI 316 stainless steel U-bend samples. The results obtained show that the behaviour of chromium and oxygen in passive films formed on 316 steel in the stress field was nearly similar to that formed on 302 steel. Concerning the molybdenum diffusion outwards the passive film formed on the 316 steel was reduced by either the tensile or compressive stress field.     

Mid-frequency PECVD of a-SiCN:H films and their structural,mechanical and electrical properties

The mid-frequency pulsed plasma enhanced chemical vapour deposition (PECVD) of hydrogenated amorphous silicon carbonitride (a-SiCN:H) was investigated to prove the suitability of these films as a mechanical stiff insulator for the integration of piezoelectric fibres in microstructured aluminium plates. For the a-SiCN:H deposition trimethylsilane (SiH(CH₃)_3; 3MS) and nitrogen in mixture with argon were used. The films were characterised regarding their deposition rate, elastic modulus and hardness (nanoindentation), mechanical stress, elemental composition (ERDA) and electrical insulating properties.The breakdown field strength of μm-thick a-SiCN:H films is in the range of 2–4 MV/cm. At pressures of a few Pa the deposition rate reached values up to 6 μm/h. It is limited by the power absorption in the 100 kHz bipolar-pulsed discharge. Varying the pressure from 2 Pa to 15 Pa has only little influence on the film composition. With increasing pressure during deposition the elastic modulus of the films decreases from about 146 GPa to 100 GPa and the compressive film stress from 1.2 GPa to 0.55 GPa. By reducing the 3MS flow rate from 50 sccm to 10 sccm (at 8 Pa deposition pressure), the carbon and the hydrogen concentrations in the films were reduced by about 10 at. %. The Si-content is only slightly reduced but the N-content is more than tripled. In contrast, the changes in the mechanical film properties are comparatively small. The mechanical properties of a-SiCN:H films are not simply correlated to the stoichiometry but are rather controlled by the ion bombardment during growth.     

Formation of β-FeSi2 thin films on non-silicon substrates

β-FeSi₂ films were prepared on non-silicon substrates by sputtering. The crystalline growth, stress induced cracks and adhesive ability to the substrate were investigated on substrate temperature and thermal expansion coefficient of substrate materials. It was found that crack formation in β-FeSi₂ films was dependent on the thermal expansion coefficients of CaF₂, MgO and quartz glass insulating materials. High-density cracks were observed from β-FeSi₂ films on CaF₂ and quartz glass substrates with large difference of the thermal expansion coefficient between β-FeSi₂ film and substrate materials, and it was crack-free on MgO substrate with a thermal expansion coefficient close to that of β-FeSi₂ films. Polycrystalline β-FeSi₂ films grew on Mo, Ta, W, Fe and stainless steel (SS) substrates at low substrate temperature around 400 °C. There was no α-FeSi₂ phase confirmed in the films. All the films had continuous structures without noticeable cracks even though they have different thermal expansion coefficients. Capacity-voltage measurements showed that β-FeSi₂ films formed on SS substrates has n-type conductivity, with residual carrier concentrations of about 1.3∼6.4 × 10¹⁸ cm^− 3. Auger electron spectroscopy depth profile measurements identified homogeneous distribution of Fe and Si atoms in the film region, but with a large interface region between the film and the substrate.     

Mechanical properties optimization of tungsten nitride thin films grown by reactive sputtering and laser ablation

Transition metal nitrides coatings are used as protective coatings against wear and corrosion. Their mechanical properties can be tailored by tuning the nitrogen content during film synthesis. The relationship between thin film preparation conditions and mechanical properties for tungsten nitride films is not as well understood as other transition metal nitrides, like titanium nitride. We report the synthesis of tungsten nitride films grown by reactive sputtering and laser ablation in the ambient of N₂ or N₂/Ar mixture at various pressures on stainless steel substrates at 400  C. The composition of the films was determined by XPS. The optimal mechanical properties were found by nanoindentation based on the determination of the proper deposition conditions. As nitrogen pressure was increased during processing, the stoichiometry and hardness changed from W₉N to W₄N and 30.8-38.7 GPa, respectively, for films deposited by reactive sputtering, and from W₆N to W₂N and 19.5-27.7 GPa, respectively, for those deposited by laser ablation.     

X-ray diffraction study of thermal stress relaxation in ZnO films deposited by magnetron sputtering

X-ray diffraction stress analyses have been performed on two different thin films deposited onto silicon substrate: ZnO and ZnO encapsulated into Si₃N₄ layers. We showed that both as-deposited ZnO films are in a high compressive stress state. In situ X-ray diffraction measurements inside a furnace revealed a relaxation of the as-grown stresses at temperatures which vary with the atmosphere in the furnace and change with Si₃N₄ encapsulation. The observations show that Si₃N₄ films lying on both sides of the ZnO film play an important role in the mechanisms responsible for the stress relaxation during heat treatment. The different temperatures observed for relaxation in ambient and argon atmospheres suggest that the thermally activated stress relaxation may be attributed to a variation of the stoichiometry of the ZnO films. The present observations pave the way to fine tuning of the residual stresses through thermal treatment parameters.     

Structural and mechanical properties of multi-element (AlCrMoTaTiZr)Nx coatings by reactive magnetron sputtering

(AlCrMoTaTiZr)N_x high-entropy films were deposited on silicon wafer and cemented carbide substrates from a single alloy target by reactive RF magnetron sputtering under a mixed atmosphere of Ar and N₂. The effect of nitrogen flow ratio R_N on chemical composition, morphology, microstructure, and mechanical properties of the (AlCrMoTaTiZr)N_x films was investigated. Nitrogen-free alloy film had an amorphous structure, while nitride films with at least 37 at.% N exhibited a simple NaCl-type FCC (face-centered cubic) structure. Mixed structures occurred in films with lower nitrogen contents. Films with the FCC structure were thermally stable without phase decomposition at 1000 °C after 10 h. The (AlCrMoTaTiZr)N film deposited at R_N = 40% exhibited the highest hardness of 40.2 GPa which attains the superhard grade. The main strengthening mechanisms for this film were grain-size and solid-solution strengthening. A residual compressive stress of 1.04 GPa was small to account for the observed hardness. The nitride film was wear resistant, with a wear rate of 2.8 × 10^− 6 mm³/N m against a loaded 100Cr6 steel ball in the sliding wear test. These high-entropy films have potential in hard coating applications.     

Effects of different needles and substrates on CuInS2 deposited by electrostatic spray deposition

Copper indium disulphide (CuInS₂) thin films were deposited using the electrostatic spray deposition method. The effects of applied voltage and solution flow rate on the aerosol cone shape, film composition, surface morphology and current conversion were investigated. The effect of aluminium substrates and transparent fluorine doped tin oxide (SnO₂:F) coated glass substrates on the properties of as-deposited CuInS₂ films were analysed. An oxidation process occurs during the deposition onto the metallic substrates which forms an insulating layer between the photoactive film and substrate. The effects of two different spray needles on the properties of the as-deposited films were also studied. The results reveal that the use of a stainless steel needle results in contamination of the film due to the transfer of metal impurities through the spray whilst this is not seen for the glass needle. The films were characterised using a number of different analytical techniques such as X-ray diffraction, scanning electron microscopy, Rutherford back-scattering and secondary ion mass spectroscopy and opto-electronic measurements.     

Composition and optical properties of silicon nitride films grown on SiO2-glass and R-Al2O3 substrates by reactive RF magnetron sputtering

We have grown silicon nitride (Si₃N₄) films on SiO₂-glass and R-Al₂O₃ substrates by using reactive RF magnetron sputtering deposition methods with N₂ pure gas and N₂ + Ar mixture gas. The film composition, thickness and impurities have been examined by ion beam analysis. It is shown that the films have stoichiometric composition and are free from Ar contamination, when N₂ gas was used for the film deposition. Effects of impurities on the film properties, e.g., optical properties will be discussed.     

Degradation behavior of amorphous silicon nitride fibers in low atmospheric pressure

We investigated the degradation behavior of amorphous silicon nitride (Si₃N₄) fibers in low air pressure and presumed the evolution mechanism. The obtained Si₃N₄ fibers were characterized by tensile strength, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and elemental analysis after being annealed (air pressure: 1 Pa–0.1 MPa, temperature: 1000–1600 °C, dwell time: 0–4 h). When air pressure was lower than 100 Pa or higher than 1000 Pa the strength of fibers dropped sharply. Due to the moderate partial pressure of oxygen in 100–1000 Pa, both active oxidation and passive oxidation were restrained resulting in the best mechanical property of fibers in 100–1000 Pa. Besides air pressure, annealing time also affected the thermal behavior of fibers. Firstly Si₃N₄ fibers were passive oxidized to form SiO₂ layer on the surface, and then Si₃N₄ decomposed into free Si and SiO₂ released gaseous SiO. Finally crystallization inside of fibers and formation of nanowires on the outer surface played the leading role in the progress of degradation.

     

Stress and microstructure evolution during growth of magnetron-sputtered low-mobility metal films: Influence of the nucleation conditions

Large tensile stresses (up to 3 GPa) were previously observed in low-mobility metallic Mo_1 − xSi_x films grown on amorphous Si and they were ascribed to the densification strain at the amorphous-crystalline transition occurring at a critical film thickness. Here, we focus on the influence of the nucleation conditions on the subsequent stress build-up in sputter-deposited Mo_0.84Si_0.16 alloy films. For this purpose, growth was initiated on various underlayers, including amorphous layers and crystalline templates with different lattice mismatch, and the stress evolution was measured in situ during growth using the wafer curvature technique. Tensile stress evolutions were observed on amorphous SiO₂ and (111) Ni underlayers, similarly to the stress behaviour found on amorphous Si. For these series, the films were characterized by large in-plane grain size (~ 500 nm). However, on a (110) Mo buffer layer, a different stress behaviour occurred: after an initial tensile rise ascribed to coherence stress, a reversal towards a compressive steady state stress was observed. A change in film microstructure was also noticed, the typical grain size being ~ 30 nm. The origin of the compressive stress source in the metastable Mo_0.84Si_0.16 alloy grown on (110) Mo is discussed based on the stress evolutions measured at varying deposition rates and Ar working pressures, as well as in comparison with stress evolutions in pure Mo films.     

Effects of bias voltage on the microstructure and mechanical properties of (Ti,Al,Cr)N hard films with N-gradient distributions

(Ti,Al,Cr)N hard reactive films were deposited on high speed steel substrates by multi-arc ion plating (MAIP) technology using pure Cr and Ti-50Al(at.%) alloy targets. The partial pressure of N₂ was raised step by step in each deposition process. The surface morphology, the cross-sectional morphology of fracture sample, the surface compositions and the phase structure of the (Ti,Al,Cr)N films were investigated by scanning electronic microscope (SEM) and X-ray diffraction (XRD). The dense columnar microstructure was obtained in all of the (Ti,Al,Cr)N films, though micro-droplets evidently existed on the surface of the films. The micro-hardness of the film surface, the adhesive strength of the film/substrate and the thermal shock resistance were investigated. The results revealed the effects of bias voltage on the composition, phase structure, and mechanical properties. The improved balanced properties of a micro-hardness of about 50 GPa, an adhesive strength larger than 200 N and a thermal shock resistance of 7-8 cycles were reached at a bias voltage of 150 V. The present super-hard (Ti,Al,Cr)N films with N-gradient distribution may be an actual substitution of TiN, (Ti,Al)N, (Ti,Cr)N and single-layer (Ti,Al,Cr)N hard films.     

Effect of compressive stress inducing a band gap narrowing on the photoinduced activities of sol-gel TiO2 films

TiO₂ thin films grown on different kinds of substrates were obtained by sol-gel process. X-ray diffraction revealed that the TiO₂ lattice parameter c decreased continuously, indicating a continuous variation in the compressive stress, a negligible compressive stress of the film grown onto Soda-Lime Glass (SLG), medium compressive stress of the film grown onto BoroSilicate Glass (BSG) and large compressive stress of the film deposited onto the Quartz Substrate (QS). UV-Vis absorbance spectra exhibited a red-shift of the absorbance edge of the TiO₂ films suggesting a lowering of the band gap, which is a direct consequence of the increase of the compressive stress. X-ray photoelectron spectroscopy revealed that the surface composition of titania films was similar except for sodium-ion concentration. The rate observed during the photo-oxydation of the stearic acid on TiO₂/QS was twice as high as that of TiO₂/BSG and about 1000 times superior to that of TiO₂/SLG. The photoinduced wettability shows an identical dependence of the compressive stress. According to these results, the compressive stress could be used to tune the band gap of the titanium oxide in order to enhance the photoinduced properties.     

Joining Si3N4 to type 405 steel with soft metal interlayers

Abstract

The suitability of four pure metals, Ni, Fe, Ti, and Nb, as interlayers for bonding silicon nitride to type 405 ferritic stainless steel has been examined. Bonding was carried out by hot isostatic pressing at temperatures between 1473 and 1673 K under a pressure of 100 MPa. Of the metals tested, Fe and Nb formed the strongest interfacial bonds with Si₃N₄. To reduce the influence of residual stress in joints, Fe/W and Nb/W laminated interlayers were also examined. The use of W restricted the contraction of Fe or Nb, and the Si₃N₄/steel joints with these interlayers had a tensile strength of more than 50 MN m^?2. A low-pressure (10 MPa) bonding process was also used for the Fe/W interlayer.

MST/470