1,721,010 research outputs found
The influence of superimposed DC current on electrical and spectroscopic characteristics of HiPIMS discharge
No full textThe electrical characteristics and spectroscopic properties have been comprehensively investigated in a DC superimposed high power impulse magnetron sputtering (DC-HiPIMS) deposition system in this paper. The influence of superimposed DC current on the variation of target and substrate currentw aveforms, active species and electron temperatures with pulse voltages are focused. The peak target currents in DC-HiPIMS are lower than in HiPIMS. The time scales of the two main discharge processes like ionization and gas rarefaction in DC-HiPIMS are analyzed. When the pulse voltage is higher than 600 V, the gas rarefaction effect becomes apparent. Overall, the ionization process is found to be dominant in the initial similar to 00 mu s during each pulse. The active species of Ar and Cr in DC-HiPIMS are higher than in HiPIMS unless that the pulse voltage reaches 900 V. However, the ionization degree in HiPIMS exceeds that in DC-HiPIMS at around 600 V. The electron temperature calculated by modified Boltzmann plot method based on corona model has a precipitous increase from 0.87 to 25.0 eV in HiPIMS, but varies mildly after the introduction of the superimposed DC current. Additionally, the current from plasma flowing to the substrate is improved when a DC current is superimposed with HiPIMS. (c) 2018 Author(s)
Microstructure and properties of duplex coatings on magnesium alloy
No full textThe duplex Ti cold spray + MAO coatings were deposited on the Mg alloy substrates using combined cold spray and micro arc oxidation (MAO). The microstructure, mechanical property and corrosion resistance of the duplex coatings were investigated compared with the MAO coated Mg alloy substrate. Results indicate that the Ti cold spray coating with 130 mu m showed an obvious boundary between the Mg substrate, and the TiO2 phase was formed by MAO on the top coating. The duplex coating showed a little coarse and porous structure, which resulted in low mechanical property and wear resistance compared with the MAO treated Mg substrate. However, it showed an excellent corrosion resistance due to the difference of chemical stability for the coatings. Furthermore, this duplex coating might be very useful for improving the photocatalytic ability of titania due to its markedly increasing specific area
Preparation of Ti2AlC MAX Phase Coating by DC Magnetron Sputtering Deposition and Vacuum Heat Treatment
No full textconsidered as a candidate for applications as corrosion resistant and irradiation resistant protective coating. MAX phase coatings can be fabricated through firstly depositing a coating containing the three elements M, A, and X close to stoichiometry of the MAX phases using physical vapor deposition, followed by heat treatment in vacuum. In this work, Ti-Al-C coating was prepared on austenitic stainless steels by reactive DC magnetron sputtering with a compound Ti50Al50 target, and CH4 used as the reactive gas. It was found that the as-deposited coating is mainly composed of Ti3AlC antiperovskite phase with supersaturated solid solution of Al. Additionally, the ratio of Ti/Al remained the same as that of the target composition. Nevertheless, a thicker thermally grown Ti2AlC MAX phase coating was obtained after being annealed at 800 degrees C in vacuum for 1 h. Meanwhile, the ratio of Ti/Al became close to stoichiometry of Ti2AlC MAX phases. It can be understood that owing to the higher activity of Al, it diffused quickly into the substrate during annealing, and then more stable Ti2AlC MAX phases transformed from the Ti3AlC antiperovskite phase. Copyright (C) 2015, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved
Ab initio molecular dynamics simulation on stress reduction mechanism of Ti-doped diamond-like carbon films
No full textStructural properties of Ti-doped diamond-like carbon (DLC) films as a function of Ti concentrations (1.56-7.81 at.%) were investigated by ab initio molecular dynamics simulation to clarify the stress reduction mechanism. Results showed that with introducing Ti into DLC films, the residual compressive stress decreased firstly and then increased, which was consistent with the previous experimental results. Structural analysis revealed that the addition of Ti efficiently relaxed both the highly distorted bond angles and bond lengths, which led to the reduction of residual stress; the increase of residual stress at the high Ti concentration was attributed to the existence of distorted Ti-C structures and the increased fraction of distorted C-C bond lengths. (C) 2014 Elsevier B.V. All rights reserved
Effect of N Doping on Microstructure, Mechanical and Tribological Properties of V-Al-C Coatings
No full textThe crises of resource shortage have prompted ocean exploitation to spring up all over the world. Some crucial frictional components of marine equipment have to be directly faced with the conjoint action of wear and corrosion. Transition metal nitrides or carbides hard coatings have been widely used to improve tribological performance in various applications. However, the poor toughness, wear and corrosion resistance of coatings cannot meet the harsher marine environment, which needs to obtain multi-functional hard coatings providing complex properties. The nanocomposite structure coatings containing nanocrystalline phase embedded in an amorphous matrix allow tailoring their properties to desired value by designing chemical composition and nanostructure. In this work, V-Al-C and V-Al-C-N coatings were deposited on silicon and high speed steel (HSS) substrates by magnetron sputtering. The crystal microstructure, chemical composition, surface morphology, cross-sectional structure, mechanical property and friction behavior of the coatings under different contact conditions (air, distilled water and artificial seawater) were studied by XRD, XPS, SEM, nano-indentation and ball-on-disc tribometer. The results showed that the V-Al-C coating displayed columnar structure with coarse grain. When the nitrogen was incorporated, the coating structure evolved into nanocomposite structure composed of nanocrystallite and amorphous carbon. The hardness increased from (14 +/- 0.48) GPa to (24.5 +/- 0.8) GPa, and the toughness was significantly improved (H/E>0.1). In air condition, the friction coefficient decreased from 0.70 to 0.42, owing to the synergy interaction between V2O5 and amorphous carbon during sliding. The friction coefficients of the both coatings in distilled water and artificial seawater were lower than those in air owing to the boundary lubrication forming lubricative film by absorbed water. The friction coefficient in seawater was lower than those in distilled water, resulting from the formation of Mg(OH)(2) and CaCO3 during sliding. However, the wear rates of the both coatings in artificial seawater were larger than that in distilled water, which demonstrated a synergism between corrosion and wear in artificial water. The V-Al-C coating was all worn out under different contact conditions owing to severe abrasive wear, while the V-Al-C-N coating showed better wear resistance, with a wear rate of 3.0x10(-16) m(3)/(N center dot m) in air and 1.4x10(-15) m(3)/(N center dot m) in artificial water, respectively
Ab initio molecular dynamics simulation on stress reduction mechanism of Ti-doped diamond-like carbon films
No full textDISCHARGE CHARACTERISTICS OF Ti AND FILM PREPARATION USING HYBRID HIGH POWER IMPULSE MAGNETRON SPUTTERING
No full textHybrid high power impulse magnetron sputtering (HIPIMS) is a new-generation HIPIMS technique with a pulse and dirrect current power supply parallelled connection operation. In this work, the influence of dirrect current from 0 to 4.0 A supplied by the dirrect current power is investigated on hybrid HIPIMS Ti discharge characteristics, plasma parameters (plasma potential, electron temperature and electron density) and Ti film properties in an Ar atmosphere. The results show that target voltage and current are characterized by a peak with variation of time in different dirrect currents. Although the target voltage is barely affected, the target current decreases with increasing the dirrect current during the pulse turn-on stage. The plasma parameters determined by a Langmuir probe have been significantly influenced by the dirrect current. Moreover, the deposition rate and average roughness increase while the hardness and elastic modulus have a slight decrease with the variation of dirrect current from 1.0 to 3.0 A. The samples are selected for comparison with that prepared by conventional direct current magnetron sputtering (DCMS) at the same average target power 650 and 1500 W. The results demonstrate that Ti films using hybrid HIPIMS have a close deposition rate and a superior quality and performance to those prepared using DCMS especially at the low target power 650 W when the direct current is 1.0 A
Tribological Property of Cr-B Coatings Prepared by HIPIMS Technique
No full textTo investigate the tribological behavior of Cr-B coatings under different environments(dry,distilled water and sea water conditions),the Cr-B coatings were deposited by high power impulsed magnetron sputtering technique. The composition,morphology,microstructure and mechanical properties were analyzed,and the tribological behavior of Cr-B coatings under different environments was mainly investigated.The results show that the deposited binary Cr-B coating exhibits a preferred(101)-texture with boron deficiency(B/Cr atom ratio is about 1.8),the hardness and elastic modulus were(26.91.0)GPa and(306.76.0)GPa,respectively.The coating under the dry environment displays a high coefficient of friction of 0.75and wear rate due to the wear debris in the wear track that lead to serious abrasive wear.However,under the distilled water and sea water environments,the coating shows a relatively low friction coefficient of 0.26in distilled water and 0.22in sea water because of the formed boundary lubrication.Meanwhile,the wear mechanism under the distilled water environment is abrasive wear,while under the sea water condition,it attributes to the synergistic effect of abrasive wear and corrosion wear
Influences of Different Interlayers on Mechanical and Tribological Properties of DLC Films
No full textAdhesion between the film and the substrate is a key factor to determine the performance of the films.Due to the low adhesion of diamond-like carbon(DLC)film on cemented carbide,the DLC films with different W interlayer(single W layer,single WC layer,W bilayer,and W trilayer)were deposited on cemented carbide YG8substrate by a novel linear ion beam source composited with a DC magnetron sputtering process.The mechanical and tribological properties of DLC films were evaluated.The results show that the DLC films with different W interlayers are dense,and the interfacial columnar structure with the increased layers is interrupted,which is conducive to improve the toughness of DLC films.For the DLC film with W trilayer,its the biggest toughness is 6.44MPa·m~(1/2). The hardness decreases, howerver,the residual stress can be reduced by 55%compared to the film with single W layer and the adhesion strength reaches to 85N.Additionally,this film has lower friction coefficient and wear rate,which exhibits excellent anti-wear and anti-friction properties
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