The structure, surface topography and mechanical properties of Si-C-N films fabricated by RF and DC magnetron sputtering

Silicon carbon nitride thin films were deposited on Co-Cr alloy under varying deposition conditions such as sputtering power and the partial pressure ratio of N₂ to Ar by radio frequency and direct current magnetron sputtering techniques. The chemical bonding configurations, surface topography and hardness were characterized by means of X-ray photoelectron spectroscopy, atomic force microscopy and nano-indentation technique. The sputtering power exhibited important influence on the film composition, chemical bonding configurations and surface topography, the electro-negativity had primary effects on chemical bonding configurations at low sputtering power. A progressive densification of the film microstructure occurring with the carbon fraction was increased. The films prepared by RF magnetron sputtering, the relative content of the Si-N bond in the films increased with the sputtering power increased, and Si-C and Si-Si were easily detachable, and C-O, N-N and N-O on the film volatile by ion bombardment which takes place very frequently during the film formation process. With the increase of sputtering power, the films became smoother and with finer particle growth. The hardness varied between 6 GPa and 11.23 GPa depending on the partial pressure ratio of N₂ to Ar. The tribological characterization of Co-Cr alloy with Si-C-N coating sliding against UHMWPE counter-surface in fetal bovine serum, shows that the wear resistance of the Si-C-N coated Co-Cr alloy/UHMWPE sliding pair show much favourable improvement over that of uncoated Co-Cr alloy/UHMWPE sliding pair. This study is important for the development of advanced coatings with tailored mechanical and tribological properties.     

Interface adhesion properties of functional coatings on titanium alloy formed by microarc oxidation method

Three functional coatings (namely Al-C, Si-P-Al and P-F-Al coating) were fabricated by microarc oxidation method on Ti6Al4V alloy in different aqueous solutions. The microstructure, phase and chemical composition of coatings were investigated using scanning electron microscope, X-ray diffraction and energy dispersive spectroscopy. The interface adhesion failure mode of the coating is revealed by shear, tensile and thermal shock methods. The coatings exhibit high adhesion strength by the quantitative shearing test, registering as 110, 70, and 40 MPa for Al-C, Si-P-Al and P-F-Al coating, respectively. The tensile test of the coated samples shows that microarc oxidation treatment does not significantly deteriorate mechanical properties of substrate titanium alloy. The observations of the coating failure after subjected to the identical tensile elongation of 3.0% are well in agreement with those results of the shear test. The thermal cycle test indicates that all the coatings have good anti-thermal shocking properties.     

碳化钨对激光熔覆高熵合金的影响

为了获得高性能的涂层材料,采用激光熔覆的方法,在Q235钢基体上制备了FeSiCrCoMo高熵合金涂层,并研究了WC对高熵合金涂层的组织和性能的影响。通过金相、X射线衍射、扫描电镜、硬度计、磨损试验机分别研究了添加WC前后涂层的微观形貌、相结构、硬度及磨损性能。结果表明:高熵合金FeSiCrCoMo涂层组织为粗大枝状晶,主要由BCC相和金属间化合物构成,添加WC后,涂层中形成了致密细小的胞状晶,同时BCC相增多,金属间化合物明显减少;添加WC后涂层的硬度明显增强,平均硬度提升了23%,涂层表面平均硬度达到了687HV0.2;WC的添加使得涂层的摩擦系数减小,磨损率减小,耐磨性能提高。     

Parametric study of Al and Al2O3 ceramic coatings deposited by air plasma spray onto polymer substrate

Aluminum and ceramic (Al₂O₃) coatings were deposited onto the polymer substrate by air plasma spray (APS) to improve the mechanical properties of the polymer surface. The effect of spray parameters (current and spray distance in this paper) on the phase composition, microstructure and mechanical properties was investigated. Shear adhesion strength between the coatings and the substrates was also examined. The results indicate that the deposition parameters have a significant effect on the phase composition, microstructure and mechanical properties of as-spayed coatings. The maximum shear adhesion strength of the bond coats was 5.21 MPa with the current of 180 A and 190 mm spray distance.     

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利用化学气相反应法对掺杂石墨材料进行了SiC梯度涂层,研究了SiC梯度涂层对掺杂石墨材料热力学性能以及微观结构的影响。获得了约100μm的SiC涂层,涂层后的材料导热性能下降,而机械强度有所增加。对涂层表面的物相成分分析表明,除了SiC之外,还有少量的单质Si。厚膜SiC梯度涂层的掺杂石墨材料在HT-7托卡马克装置中经等离子体放电实验后,SiC的颗粒形貌发生了明显的变化,涂层厚度下降到约30μm。     

Effect of spraying power on the microstructure and mechanical properties of supersonic plasma-sprayed Ni-based alloy coatings

The aim of this paper was to investigate the microstructure and mechanical properties of the supersonic plasma-sprayed Ni-Cr-B-Si-C coatings prepared at different spraying powers. The microstructure, phase composition, porosity, Young's modulus, micro-hardness, and residual stresses of the coatings were investigated and determined. The variations of the porosity, Young's modulus and micro-hardness of the coatings were evaluated by using statistical method. Results showed that the variations of porosity, Young's modulus and micro-hardness of the coatings followed the Weibull distributions. With increasing the porosity, the micro-hardness and Young's modulus of the coating decreased. The mean value of the Young's modulus of the coating calculated from Weibull plot was almost proportional to the square root of the micro-hardness of the coating. With increasing the power, Young's modulus of the coating increased, which, in turn, resulted in the increment of the residual stress at the coating surface.     

Influence of annealing treatment on the microstructure and mechanical performance of cold sprayed 304 stainless steel coating

In this study, 304 stainless steel coatings were deposited on interstitial-free steel substrate by cold spraying method. The effect of annealing treatment on microstructure, microhardness, ultimate tensile strength and fracture performance of the coatings were studied. The results showed that annealing treatment had made a dominant contribution to heal up the incomplete interfaces between the deposited particles. Both of the microstructure and the mechanical properties have been obviously optimized by annealing treatment. In addition, the coating microhardness decreased from 345 HV_0.2 for the as-sprayed coating to 201 HV_0.2 for the annealed coating. The coating ultimate tensile strength increased from 65 MPa for the as-sprayed coating to 357 MPa for the annealed coating, which resulted from the increase of the metallurgically bonded areas in the coating induced by annealing treatment. Fracture morphology of the coatings also revealed that annealing treatment changed the fracture character of the cold sprayed 304 stainless steel coating from brittle type to plastic type.     

Influence of FeSO4 concentration on thermal emissivity of coatings formed on titanium alloy by micro-arc oxidation

Ceramic coatings with high emission were fabricated on Ti6Al4V alloy by microarc oxidation (MAO) with additive FeSO₄ into the electrolyte. The microstructure, chemical composition and chemical state of the coatings were determined by SEM, XRD, EDS and XPS, respectively. The bonding strength between the coating and substrate was studied by tensile strength test, together with the thermal shock resistance of the coating. The results showed that Fe content in the coating layer significantly affect its thermal emissivity. The relative content of Fe in the coatings surface increased at first and then decreased with increasing the concentration of FeSO₄ in electrolytes, so does the emissivity of the coatings. The bonding strength became weaker with increasing the concentration of FeSO₄. In addition, the coating remains stable over 40 cycles of thermal shocking. The coating formed at 3 g/L FeSO₄ demonstrates the highest an average spectral emissivity value around of 0.87, and bonding strength higher than 33 MPa.     

Wear resistance of reactive plasma sprayed and laser remelted TiB2-TiC0.3N0.7 based composite coatings against medium carbon steel

Wear resistance of reactive plasma sprayed TiB₂-TiC_0.3N_0.7 based composite coatings and the as-sprayed coating with laser surface treatment was investigated using plate-on-plate tests. Wear tests were performed at different normal loads and sliding speeds under dry sliding conditions in air. The surface morphologies of counterparts against as-sprayed and laser remelted coatings were investigated. The microstructure and chemical composition of wear debris and coatings were studied using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The results show that the wear resistance of the laser remelted coating is improved significantly due to their increased microhardness and reduced flaws. The primary wear mechanism of the remelted coating is oxidation wear and its minor wear mechanisms are grain abrasion and fatigue failure during the course of wear test. In contrast, the primary wear mechanism of the as-sprayed coating is grain abrasion at the low sliding speed (370 rpm) and fatigue failure at the high sliding speed (549 rpm). The oxidation wear mechanism is a minor contributor for the as-sprayed coating.     

Synthesis and microstructure observation of titanium carbonitride nanostructured coatings using reactive plasma spraying in atmosphere

In the present study, nanostructured titanium carbonitride (TiCN) coatings were successfully deposited by reactive plasma spraying (RPS) technology using a self-designed gas tunnel mounted on a normal plasma spray torch. The phase composition and microstructure of the TiCN coatings were characterised by XRD, SEM and TEM. The results indicated that the main phase of the coatings was FCC TiC_0.2N_0.8 with a small amount of Ti₃O. The coating that was deposited using 35 kW displayed better microstructure and properties. The coating exhibited a typical nanostructure including 90 nm diamertrical equiaxed grains and 400 nm long columnar grains by TEM images. The SEM observation further revealed that the equiaxed grains in parallel direction to the substrate surface in TEM images were actually the columnar grains perpendicular to the substrate surface. The formation mechanism of the nanostructured coatings was also discussed. The measured microhardness value of the coating was approximately 1659 Hv_100 g, and the calculated crack extension force was about 34.9 J/m².     

Improvement in the properties of plasma-sprayed metallic, alloy and ceramic coatings using dry-ice blasting

Dry-ice blasting, as an environmental-friendly method, was introduced into atmospheric plasma spraying for improving properties of metallic, alloy and ceramic coatings. The deposited coatings were then compared with coatings plasma-sprayed using conventional air cooling in terms of microstructure, temperature, oxidation, porosity, residual stress and adhesion. It was found that a denser steel or CoNiCrAlY alloy coating with a lower content of oxide can be achieved with the application of dry-ice blasting during the plasma spraying. In addition, the adhesive strength of Al₂O₃ coating deposited with dry-ice blasting exceeded 60 MPa, which was nearly increased by 30% compared with that of the coating deposited with conventional air cooling. The improvement in properties of plasma-sprayed metallic, alloy and ceramic coatings caused by dry-ice blasting was attributed to the decrease of annulus-ringed disk like splats, the better cooling efficiency of dry-ice pellets and even the mechanical effect of dry-ice impact.     

Porosity, mechanical properties, residual stresses of supersonic plasma-sprayed Ni-based alloy coatings prepared at different powder feed rates

The aim of this paper was to investigate the effect of powder feed rate (PFR) on the microstructure and mechanical properties of the supersonic plasma-sprayed Ni-Cr-B-Si-C coatings. The microstructure, porosity and mechanical properties of the coatings and the residual stresses at the coating surfaces were experimentally determined. Results showed that the variations of porosity, elastic moduli and micro-hardness of the coatings followed Weibull distribution. From the statistical trend, the porosity of the coating increased with increasing PFR. However, the elastic modulus and the micro-hardness of the coating decreased and reached local minima and then increased with increasing PFR. Elastic modulus could be generally considered to be an increasing function of micro-hardness. The mean value of the elastic modulus of the coating calculated from Weibull plot was almost proportional to the square root of the mean value of the micro-hardness of the coating. Moreover, with increasing PFR, the residual stress at the coating surface, which was mainly governed by the elastic modulus of the coating, decreased to a local minimum and then increased.     

Zirconia coatings deposited by electrostatic spray deposition A chemical approach

The present study is focused on the preparation of zirconia-based coatings obtained by Electrostatic Spray Deposition (ESD). Microstructural properties of ESD coatings were optimised versus the composition of the precursor solution and the substrate nature. This chemical approach includes the influence of zirconia precursors, yttrium chloride, solvent mixtures, zirconia precursor concentration, additives and substrate nature in order to optimally tune the microstructure of the coating. A smooth, dense and homogeneous thin layer was successfully deposited.     

Study and simulation of the growth of solid lubricant MoSe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> coatings during pulsed laser deposition

The chemical composition and tribological properties of the thin-film diselenide molybdenum coatings deposited by pulsed laser deposition in vacuum and a rarefied inert gas (argon) atmosphere are studied. Upon deposition in a gas at a pressure of ∼2 Pa, stoichiometric coatings with improved antifriction properties as compared vacuum-deposited coatings form. However, a too strong increase in the argon pressure (to ∼10 Pa) degrades the tribological properties of the coating. Structure formation in the MoSe _x coatings grown by pulsed laser deposition on an unheated substrate is investigated. Deposition in vacuum or argon at a pressure of 2 Pa leads to formation of rather smooth coatings with a dense amorphous structure containing molybdenum nanoinclusions. Deposition at a high argon pressure results in a developed surface relief and a loose coating structure. A mathematical model is developed using the kinetic Monte Carlo method in order to describe structure formation in the coatings that grow during physical deposition of an atomic flux. A comparative analysis demonstrates satisfactory agreement between the simulated and experimentally studied structures in the coatings created by pulsed laser deposition at various gas pressures.     

Microstructure and selected properties of hot-work tool steel with PVD coatings after laser surface treatment

The paper presents the effect of HPD laser treatment on the microstructure and selected properties of the PVD CrN, (Ti,Al) and Ti(C,N) coatings deposited onto hot-work tool steel substrates. The microstructure and surface topography of the investigated samples are characteristic of the diversified morphology connected with the applied laser beam power. Employment of laser beam at 0.7 kW power to the laser treatment of samples with Ti(C,N) coatings causes clear coating adhesion growth because of the diffusive processes induced by heat release. Because of the higher value of the (Ti,Al)N absorption coefficient one can state that the observed substrate materials change and finally coatings destruction in case of those samples is the most noticeable. The moderate effect of the laser beam treatment of the hot-work tool steel with the PVD coating was observed for CrN coatings. However, for laser beam power above 0.5 kW differences in the thermal expansion coefficients of the substrate materials and coatings generate coating crackings.     

Microstructure and infrared emissivity property of coating containing TiO2 formed on titanium alloy by microarc oxidation

Ceramic coatings containing TiO₂ were formed on Ti6Al2Zr1Mo1V alloy surface by microarc oxidation (MAO) method. The microstructure, phase and chemical composition of the coatings were analyzed by SEM, XRD and EDS techniques. The coating mainly consists of rutile TiO₂ and a small amount of anatase TiO₂. The infrared emissivity values of coated and uncoated titanium samples when exposed to 700 °C were tested. It was found that the coating exhibits a higher infrared emissivity value (about 0.9) in the wavelength range of 8–14 μm than that of the uncoated titanium alloy, although which shows a slight increase from 0.1 to 0.3 with increasing exposure time at 700 °C. The relatively high infrared emissivity value of the MAO coating is possibly attributed to the photon emission from the as formed TiO₂ phase.     

The structure and tribological behaviors of CrN and Cr-Ti-N coatings

The Cr-Ti-N coatings with different composition were deposited in a medium frequency magnetron sputtering system on Si (1 1 1) substrates. The structures, surface morphology and wear properties were measured. The binary CrN coatings, formed a single-phase fcc structure with nearly random (1 1 1), (2 0 0) and (2 2 0) orientation, while for the Ti was introduced, coatings show a preferred orientation of (2 0 0). Cr-Ti-N coating shows a much smoother surface than CrN coating. Cr-Ti-N coating with 31.75% Ti content shows the best wear behavior. The excellent tribological properties of this composition coating are corresponding to the solid solution nitride structures.     

退火对AlTiN多层薄膜结构及力学性能影响

使用TiAl合金靶,利用中频反应磁控溅射系统,通过交替改变氮气流量的方法,在高速钢(W18Cr4V)基体上沉积了一组氮含量周期性改变的AlTiN多层薄膜,并分别在600,700和800 ℃下真空退火热处理. 利用X射线衍射仪、场发射扫描电镜和高分辨透射电镜等方法研究了沉积态和退火态AlTiN多层薄膜组织和微观结构;AlTiN多层薄膜的力学和膜基结合性能用纳米压痕硬度仪、摩擦磨损仪以及划痕试验仪得到. 研究表明,采用沉积过程中周期改变氮气流量的方法,可以制备出稳定的、力学性能良好的AlTiN多层薄膜. 80 关键词： AlTiN多层薄膜 退火 微观结构 力学性能     

碳纳米管增强镍磷基复合镀层研究

对CVD方法制备的碳纳米管进行表面改性处理，然后在液相中分散，利用化学共沉积方法形成碳纳米管镍磷基复合镀层，研究了碳纳米管表面改性后的红外谱、碳纳米管复合镀层的表面形貌、硬度及摩擦学行为.结果表明：碳纳米管的加入明显地提高镍磷复合镀层的硬度和改善了镍磷复合镀层的摩擦性能.硬度达到946HV，20N载荷时摩擦系数为0.7，增至80N时降为0.6；相同条件下与传统耐磨材料SiC增强的镍磷基复合镀层相比，具有更低的摩擦系数和磨损量. 关键词： 碳纳米管 表面改性 复合镀层 摩擦行为     

Structure, hardness and corrosion behavior of a gradient CrNx thick coating applied to turbine blades

In order to protect turbine blades from solid particle erosion, a gradient CrN_x coating was deposited on 10% Cr heat-resistant steel by ion plating; the thickness of the coating was about 40 μm. The chemical composition, microstructure and nano-hardness of gradient CrN_x coating were analyzed. The bonding force was determined using scratch test. The potentiodynamic polarization and high-temperature oxidation tests were respectively conducted to investigate the corrosion behavior. The results indicate that gradient variation of phase structure, chemical composition and nano-hardness in the coating is found, and the bonding force with substrate is excellent. The microstructure obtained can enhance the corrosion performance of the substrate. The corrosion resistance improvement is not only attributed to the increase of coating in thickness, but also to internal microstructure and chemical composition of coating. Based on SEM and TEM observations, the cross-sectional fracture of the coating shows nano-crystalline and fine columnar crystalline structures. There are no penetrable pinholes, which could validly reduce the electrolyte transferring to inner substrate. In addition, the corrosion resistance of coating is further improved by the formation of nitrogen and chromium rich transition layers.