Multilayered decorative a-C:H/CrC coating on stainless steel

A nano-structured multilayer coating of a combination of a soft layer (a-C:H) produced by PECVD together with a hard layer (Cr/Cr_3 − xC_x) produced by PVD allows to tailor the coating properties by choosing the thickness of the individual layers. The resulting coating is well adherent, may have the elastic properties compatible with the substrate and is much harder than the substrate. The best coating properties were found for about 7-8 nm thick layer thickness for both CrC/Cr and a-C:H. The adhesion (L_C1 > 30 N) and abrasion resistance (Rösler test > 1 h) indicate a coating resistant to normal handling of a handheld consumer product. The colour of the coating may be chosen by adjusting the thickness of the top Cr layer between black (5 nm thick Cr layer) and metallic Cr like (> 30 nm thick Cr layer). The colour and the adhesion (as verified by tape test) did not change during a 6 d humidity cycle tests or 3 month exposure to normal atmospheric conditions.     

Relation of the polymeric ion species in plasma to the hardness of a-C:H film made by PSII&D

The amorphous carbon (a-C:H) films formed by plasma source ion implantation and deposition (PSII&D) have expanded the tribological properties. Especially, the hardness can be widely changed by adequately selecting RF power, pulse bias voltage, gas species and gas pressure. Previously, we reported that a-C:H film hardness depended on the electron temperature in C₂H₂ plasma which was ignited with pulsed RF power, and that the hardness was in inverse proportion to the electron temperature in the range of less than 2.5 eV. We have discovered that the film hardness is, in some cases, changing even if the electron temperature is constant. This suggests that there are some new factors to determine the film hardness besides the electron temperature in the plasma. In this study, we employ a quadrupole mass spectrometer to measure the intensity of each polymeric ion in C₂H₂. The film hardness is determined by the synergy of the polymeric ion abundances and ion irradiation.     

Microstructure and tribology of TiC(Ag)/a-C:H nanocomposite coatings deposited by unbalanced magnetron sputtering

TiC(Ag)/a-C:H nanocomposite coatings with various Ag concentrations were fabricated on Si p(100) substrates. The composition and structure of as-deposited nanocomposite coatings were systemically investigated, and the friction and wear behaviors were also evaluated under the ambient, high temperature and high vacuum, respectively. Results show that the TiC nanocrystallites were formed in the amorphous hydrogenated carbon matrix near the substrate. The co-dopant Ag possessed nanocrystalline structure in the as-fabricated coatings whilst it formed Ag clusters (10–50 nm) on the surface. Furthermore, the introduction of Ag caused a significant reduction in the residual compressive stress without considerable decrease of the hardness and improved the adhesive strength of nanocomposite coatings. Tested as-deposited and after annealed at 500 °C coatings, the TiC(Ag)/a-C:H coatings showed a reduction of friction coefficients and wear rates with increment of Ag concentration. Under high vacuum condition, the TiC(Ag)/a-C:H coatings presented superlow friction behavior where the friction coefficient was reduced from 0.01 to 0.005 and lifetime increased from 0 to 1500 cycles. The significant improvement in tribological properties was mainly attributed to the low shear strength of Ag clusters on the surface as well as Ag diffusion to surface and wear track of coatings. The superior friction and wear behaviors of TiC(Ag)/a-C:H coatings make them good candidates as solid lubrication materials in space and aircraft applications.     

Microstructure and tribological properties of the a-C:H films deposited by magnetron sputtering with CH4/Ar mixture

Hydrogenated amorphous carbon (a-C:H) films were deposited on steel and silicon wafers by unbalanced magnetron sputtering under different CH₄/Ar ratios. Microstructure and properties of the a-C:H films were investigated via Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Atomic force microscopy (AFM) and substrate curvature method. The results revealed that CH₄/Ar ratio played an important role in the H content but acted a little function on the sp³/sp² ratio of the films. Also, the internal stress of those films was relatively low (< 1 GPa), and the deposition rate decreased firstly and then increased with the decrease of the CH₄ fraction. The film deposited under CH₄/Ar = 1/1 (55 sccm/55 sccm) with moderate sp³ C-H / sp³ C-C had the best tribological properties. The composition, microstructure and properties of the a-C:H films were strongly dependent on the deposition process and composition of reactant gases.     

Effect of Ti Incorporation on the Microstructure and Properties of the a-C:H Films Deposited by Magnetron Sputtering Technique

Amorphous hydrogenated carbon(a-C:H)and Ti-incorporated a-C:H(Ti/a-C:H)films were deposited by magnetron sputtering with a mixture gas of CH4 and Ar.The effect of the Ti incorporation on the chemical composition,microstructure and properties of the as-deposited and the annealed films were investigated by various techniques.It has been shown that the bonding structure and the internal stress were sensitive to the incorporation of the Ti atoms.The results of the XPS revealed that the concentration of Ti atom on the surface of the film increased when the Ti/a-C:H film annealed at 300oC.The tribologcial properties of the(Ti/)a-C:H films changed greatly after annealed,due to the graphitization,oxidation of carbon,and so forth.It compared and discussed in detail the change of the microstructure and properties of the a-C:H and Ti/a-C:H films before and after annealed     

The effect of deep-case oxygen hardening on the tribological behaviour of a-C:H DLC coatings on Ti6Al4V alloy

A new duplex surface treatment combining the boost diffusion oxidation (BDO) treatment with amorphous hydrogenated diamond-like carbon hard coatings (BDO/a-C:H DLC) has been developed. Experiments results demonstrated that the BDO pre-treatment can effectively improve the scratch resistance and load bearing capacity of a-C:H DLC on Ti6Al4V. This is mainly because the hardened case in Ti6Al4V conferred by the BDO treatment can provide adequate mechanical support for the thin hard top carbon coating.     

Characterization of fatigue and adhesion properties of a-C:H/CrN coatings on bearing rings by impact tests

The impact test is used for the quantitative assessment of various properties of thin hard coatings, deposited on machine elements, tools etc. This test is mainly applied on coated specimens with simple geometries such as of cutting inserts and coated plates. In the described investigations, perpendicular and inclined impact tests were conducted directly on PVD coated bearing rings. The tests were performed with the aid of appropriate fixtures on the internal cylindrical surface of the outer bearing ring, as well as on the external one of the inner ring. Through a developed FEM simulation of the contact between the indenter ball and the cylindrical ring surfaces during the perpendicular and the inclined impact test, the film fatigue endurance stress was determined and the coating's adhesion was quantified. The mechanical properties of the applied thin films and substrates, used in the FEM calculations, were detected by nanoindentations and appropriate results evaluation. The obtained film fatigue endurance stress of the investigated coating can be considered as adequate however the coating adhesion is assessed as poor.     

Ti层对316L不锈钢表面TiB2薄膜结合力的影晌

基于多层膜优异的力学性能,采用磁控溅射法在316L不锈钢基体表面沉淀[Ti／TiB2]。（n=1,2,3）多层膜以增强TiB2薄膜的膜基结合强度。研究周期数对多层膜的结构、硬度及结合力的影响。结果表明：TiB：单层膜表现为（001）方向的织构。随着周期数的增加,多层膜的织构方向由（001）转变为（100）;多层膜的硬度从20GPa增加到26GPa,但略低于TiB2单层膜的硬度（33GPa）;相对于单膜的膜基结合力（9．5N）,多层膜表现出较好膜基结合力,最大结合力可达24N。     

离子源功率对a-C:H(Al)薄膜结构及性能的影响

目的研究离子源功率对a-C:H(Al)薄膜结构及性能的影响。方法采用阳极离子源离化CH_4气体,中频磁控溅射Al靶,通过改变离子源功率,在n(100)型单晶硅及16Mn Cr5钢基体上沉积a-C:H(Al)薄膜。利用扫描电镜、维氏显微硬度计、摩擦磨损试验机和表面轮廓仪等设备对a-C:H(Al)薄膜的结构及性能进行表征。结果薄膜的硬度均在1000HV以上。摩擦系数较低,为0.05~0.15。离子源功率为450 W时,薄膜摩擦系数和结合力均出现了最优值,分别为0.05和21.46 N。离子源功率在550 W时,磨损率达到最低值,为3.59×10~(-7) mm~3/(N·m)。结论离子源功率较低时,薄膜表面较疏松,随着离子源功率的增加,薄膜逐渐趋于平整致密。随离子源功率的增加,薄膜的硬度增大,薄膜的结合力先增大后减小,而薄膜的摩擦系数先减小后增大,磨损宽度减小,磨损深度降低,磨损率减小。     

Influence of individual Cr-C layer thickness on structural and tribological properties of multilayered Cr-C/a-C:Cr thin films

Multilayered Cr-C/a-C:Cr thin films were prepared by using a hybrid technique of combined vacuum cathodic arc/magnetron sputtering/ion beam deposition. The multilayered films consisted of a dense gradient base layer and 10 bi-layers of Cr-C (chromium matrix containing some carbon) and a-C:Cr (amorphous carbon matrix containing a small amount of chromium). The thickness of individual a-C:Cr layer was kept constant at about 18.5 nm, while that of individual Cr-C layer varied from 11.1 to 55.1 nm. It was found that an increase of the individual Cr-C layer thickness from 11.1 to 40 nm resulted in increase in material nanohardness from 7.6 to 13.6 GPa and Young's modulus from 107 to 164.8 GPa. However, a further increase in the individual Cr-C layer thickness to 55.1 nm led to decrease in nanohardness to 9.5 GPa and Young's modulus to 142.4 GPa. The scratch tests indicate that the adhesion strengths between the films and substrates are dramatically improved through the multilayered structure, acquiring critical loads exceeding 80 N. The results of pin-on-disk tests show that the lowest wear rate 1.35 × 10^− 6 mm³/Nm was achieved from the coated sample with the individual Cr-C layer thickness of about 40 nm.     

不同气体流量比对Cu/a-C∶H复合薄膜结构及摩擦学性能的影响

采用磁控溅射技术结合等离子体气相沉积技术,通过调节CH₄与Ar的气体流量比例,获得了不同Cu含量的Cu/a-C∶H复合薄膜。采用XPS、Raman等表征方法分析了不同气体流量比对Cu在复合薄膜中的存在形式及薄膜结构的影响,利用纳米压痕仪测量了复合薄膜的硬度与弹性模量,采用往复式摩擦磨损试验机、白光干涉仪、FESEM等分析了复合薄膜在空气中的摩擦学性能及相关机理。结果表明:随着CH₄在混合气体中所占比例增加,复合薄膜中sp²C含量升高,Cu含量降低,Cu晶粒的尺寸变小,复合薄膜的硬度逐渐升高,韧性降低。CH₄气体流量比为60%、Cu含量为 6.68at%的复合薄膜具有较高的硬度、良好的韧性以及在空气中最低的摩擦因数(0.091)与磨损率(1.77×10^-6 mm³·N^-1·m^-1),这与复合薄膜中sp²C含量及Cu纳米粒子的尺寸和含量有关。     

Effect of Methane Flow Rate on Growth and Properties of TiSi-C:H Films Deposited by Middle-frequency Magnetron Sputtering

以甲烷为先驱气体通过中频磁控溅射Ti80Si20靶材在硅和不锈钢基底上制备TiSi-C:H薄膜,研究了甲烷流量对薄膜沉积速率、结构、力学和摩擦学性能的影响。结果表明,甲烷流量对薄膜结构、力学和摩擦学性能有显著影响,随甲烷流量增加薄膜从包含约10 nm晶的锥状纳米晶/非晶复合结构向非晶结构转变,在低甲烷流量下沉积的薄膜具有高硬度、高应力和高磨损率;在高甲烷流量下薄膜硬度和应力降低,而摩擦学性能提高。薄膜力学和摩擦学性能的变化被认为是随甲烷流量增加薄膜结构演化的结果。     

H13钢激光熔覆Co基涂层工艺优化及组织性能

采用Nd:YAG激光器在H13钢表面制备Co基合金涂层,分析扫描速度和电流强度对涂层成形质量的影响,确定最优参数。借助扫描电镜和X射线衍射仪分析了涂层组织形貌及物相组成。使用显微硬度计和摩擦磨损试验机测试了涂层截面硬度及耐磨性能。结果表明：激光熔覆扫描速度增加和电流强度降低,均可使Co基合金涂层熔高和熔宽降低,孔洞和裂纹数量减少。优化工艺参数为：扫描速度120 mm/min,电流200 A。该工艺制备涂层组织主要由细小的枝晶和共晶组成,包括γ-Co和M23C6相,涂层硬度达到610 HV0.2;耐磨性是淬火回火态H13钢的1.32倍。     

H13钢表面TiC/Co基激光修复层的显微组织与力学性能

采用激光熔覆技术在H13热作模具钢表面分别制备了Co50合金涂层和TiC/Co基复合涂层.借助XRD,SEM与显微硬度计对比分析了涂层与基材的结合状态、涂层物相组成、截面组织形貌和显微硬度分布.结果表明,Co50合金涂层和TiC/Co基复合涂层均与H13钢基材呈良好冶金结合特征.Co50合金涂层主要由初生γ-Co枝晶及其间的共晶组织组成,而TiC/Co基复合涂层主要由TiC颗粒、枝晶及细小的共晶组织组成,其组成相除含有TiC,TiCo₃和Cr₂Ni₃外,还有Cr-Ni-Fe-C等相.涂层截面显微硬度分布表明,TiC/Co基复合涂层截面平均显微硬度明显高于Co50合金涂层,分别为5520 MPa和4990 MPa,分别是H13钢基材的2.7和2.4倍.     

The structure and adhesion of hydrogenated amorphous carbon (a-C:H) films synthesized on CoCrMo alloy by plasma immersion ion implantation and deposition at different flow ratios of acetylene to argon

Hydrogenated amorphous carbon (a-C:H) film is deposited on CoCrMo alloy by plasma immersion ion implantation and deposition (PIII-D) at different flow ratios of acetylene to argon (C₂H₂/Ar). The results show that Ar fraction in the C₂H₂-Ar gas mixture has an important effect on the structure and the adhesion of the a-C:H films. When Ar fraction in the C₂H₂-Ar gas mixture is less than 50%, the fabricated a-C:H film composition transfer from graphite-like to diamond-like which contains higher sp³ binding thanks to Ar ion bombardment, and the adhesion strength decreased with the increment of Ar fraction. But when Ar fraction in the C₂H₂-Ar gas mixture is beyond 50%, the fabricated film contains more sp² bonding for thermally driven and exhibits higher adhesion strength with the increment of the Ar fraction.     

Growth of carbon nanofiber coatings on nickel thin films on fused silica by catalytic thermal chemical vapor deposition: On the use of titanium, titanium-tungsten and tantalum as adhesion layers

Coatings of carbon nanofiber (CNF) layers were synthesized on fused silica substrates using a catalytic thermal chemical vapor deposition process (C-TCVD). The effects of various adhesion layers-titanium, titanium-tungsten and tantalum-under the nickel thin film on the attachment of carbon nanofibers and their morphological properties are presented. The diameter and the thicknesses of the CNF-coatings were analyzed by scanning electron microscopy, whereas the microstructure and crystallinity of the synthesized carbon nanofibers were investigated by transmission electron microscopy and Raman spectroscopy, respectively. Specific surface areas of CNF-coatings were determined with nitrogen adsorption-desorption isotherm measurements.Using C-TCVD of ethylene at 700 °C (1 h), well-attached, entangled, quasi-crystalline platelet carbon nanofibers were synthesized with tip-type growth mode on 25 nm thick nickel films with an adhesion layer of 10 nm Ta or Ti-W. The thickness of CNF-coating was ~ 3.5 μm, and the diameter of the fibers depended on the composition of the metallic thin film stack: 20-50 nm for Ni/Ta and 80-125 nm for Ni/Ti-W. The ultimate goal is the integration of these CNF-coatings as catalyst support in microfluidic devices, for which it is important to control CNF-coating characteristics such as fiber diameter, layer thickness, specific surface area and adhesion to the surface.