Plasma Spray Deposition Enhancement of Titanium Nitride Layer Using Nitrogen-Contained Plasma Irradiation of Titanium Substrate as a Pre-spraying Method

Reactive plasma spray of TiN ceramic coating attracts much attention over the years because of its ability to deposit thick layers on various metal surfaces. However, some mechanical properties of the coating such as its hardness should be improved. In this study, initially a thin layer of titanium nitride was prepared on a titanium substrate during irradiation of titanium substrate by a thermal DC nitrogen-contained plasma jet. Then, during reactive plasma spraying, Ti particles were injected into plasma jet, converted to titanium nitride and huddled on to the substrate. This new hybrid method (primary plasma irradiation and post-reactive plasma spraying) for deposition of TiN coatings would combine the advantages of both plasma-enhanced chemical vapor deposition and reactive plasma spraying methods in part. It resulted in a thick and hard layer of titanium nitride film. Sample produced by this method was analyzed with x-ray diffraction confirming titanium nitride production. Vickers hardness was measured using optical microscopy which was around 1319 H_v300g. To study the cross section of the layer, optical microscopy and scanning electron microscopy (SEM) were used.     

TiN-TiB2 composite coatings reactively produced by electrothermally exploded powder spray

Composite coatings composed of titanium nitride, TiN, and diboride, TiB₂, were reactively produced by the electrothermally exploded powder spray technique, in which feedstock powder was prepared from titanium and boron nitride particles. The microstructure of the coating was composed of titanium-ceramic particles the size of which were on the order of several nanometers to a few hundred nanometers. Such reactive thermal spraying brought base-metal saturation into a coating layer at the early stages of coating formation. The ceramic composite spray using feedstock of TiN and TiB₂ particles preferentially brought a new phase of cubic titanium boronitride together with TiN and TiB₂ into a coating. On comparing such a coating to one produced by the conventional method, the reactive thermal spray coating was richer in TiN and TiB₂ due to the excess nitrogen in the feedstock.     

The yttrium effect on the corrosion resistance of CO2-laser processed MCrAlY coatings

To improve the corrosion resistance and to study the effect of yttrium in the behavior of coatings produced by thermal spraying MCrAlY (M=Ni, Co) powders, CO₂ laser processing was conducted. Three methods were used: (1) a combination of gas flame and plasma spraying in air followed by laser glazing in argon, (2) low-pressure plasma spraying (LPPS) and laser glazing in argon, and (3) LPPS and laser-gas (O₂) alloying. Laser glazing in argon of the MCrAlY coatings sprayed in air promoted formation of weakly adherent agglomerates of Al–Y oxides and an alumina-chromia solid solution. Glazing in argon atmosphere of LPPS CoNiCrAlY and NiCrAlY coatings caused the formation of nickel aluminides besides the formation of Y–Al compounds. Gas (O₂)-alloying of these coatings produces continuous and adherent (yttrium-containing) alumina and chromia layers. The effects of yttrium on the characteristics of the oxides formed in the coatings during laser glazing, laser-gas alloying, and high-temperature oxidation is discussed. This work also investigated the oxidation resistance of the laser-processed MCrAlY coatings in air and in the presence of 85 mol/o V₂O₅–Na₂SO₄ fused salt at 900°C.     

Hardness, microstructure and surface characterization of laser gas nitrided commercially pure titanium using high power CO2 laser

Surface nitriding of commercially pure (CP) titanium was carried out using high power CO ₂ laser at pure nitrogen and dilute nitrogen (N ₂ + Ar) environment. The hardness, microstructure, and melt pool configuration of the laser melted titanium in helium and argon atmosphere was compared with laser melting at pure and dilute nitrogen environment. The hardness of the nitrided layer was of the order of 1000 to 1600 HV. The hardness of the laser melted titanium in the argon and helium atmosphere was 500 to 1000 HV. Using x-ray analysis the formation of TiN and Ti ₂ N phase was identified in the laser nitrided titanium. The presence of nitrogen in the nitrided zone was confirmed using secondary ion mass spectroscopy (SIMS) analysis. The microstructures revealed densely populated dendrites in the sample nitrided at 100% N ₂ environment and thinly populated dendrites in dilute environment. The crack intensity was large in the nitrided sample at pure nitrogen, and few cracks were observed in the 50% N ₂ + 50% Ar environment.     

常压和低压环境下反应等离子喷涂Al/Fe2O3复合材料的合成机理(英文)

反应等离子喷涂(RPS)技术被广泛用于制备不同使用需求的高性能涂层材料。基于经典的铝热反应原理,采用反应等离子喷涂技术分别在近常压和低压环境下制备了Al-Fe₂O₃涂层,通过XRD、SEM和EDS等分析方法对所制备涂层的相组成和显微结构进行了表征。阐明了Al和Fe₂O₃在加热和反应等离子喷涂过程中的反应机理。DTA分析结果表明,氩气氛下长时间热处理产物主要为Fe、Al₂O₃和FeAl相。然而,在等离子喷涂过程中,低氧分压环境导致中间产物FeAl₂O₄铁尖晶石相的生成,由于近常压等离子喷涂过程的冷却速度极快,该相可以保留在最终涂层结构中。而低压反应等离子喷涂等离子体射流飞行距离长,还原性气氛和较长的反应时间将其进一步还原为FeAl相。     

Thermal-sprayed Fe-10CM3P-7C amorphous coatings possessing excellent corrosion resistance

An alloy of Fe-10Cr-13P-7C was thermally sprayed by three different processes: (1) 80 kW low-pressure plasma spraying (LPPS), (2) high-velocity oxyfuel (HVOF) spraying, and (3) 250 kW high-energy plasma spraying (HPS). The as-sprayed coating obtained by the LPPS process was composed of an amorphous phase. In contrast, the as-sprayed coatings obtained by the HVOF and HPS processes were a mixture of amorphous and crystalline phases. The as-sprayed coatings showed a high hardness of 700 DPN. A very fine structure composed of ferrite, carbide, and phosphide was formed, producing a maximum hardness of greater than 1000 DPN in the LPPS coating just after crystallization on tempering. The corrosion re-sistance of the amorphous coating was superior to a SUS316L stainless steel coating in 1N H₂SO₄ solution and 1N HC1 solution. Furthermore, the amorphous coating underwent neither general nor pitting corro sion in1NUCI solution and 6% FeCl₃ 6H₂O solution containing 0.05N HCl, whereas the SUS316L stain less steel coating was attacked aggressively.     

Study on Reactive Atmospheric Plasma-Sprayed In situ Titanium Compound Composite Coating

A titanium composite coating containing in situ synthesized oxides or nitrides was deposited on mild steel by reactive atmospheric plasma spraying. The relationships between the porosity, hardness, the phase composition of the sprayed coatings, and the spraying parameters were investigated. Titanium powders were used as starting powder materials. XRD analysis and microhardness test revealed that titanium oxides and nitrides were synthesized during the spraying process. The longer the spraying distance, the more the Ti nitrides’ content in the coating. It is shown that the Ti nitrides’ content has a significant influence on coating hardness. An in situ titanium composite coating with a hardness value of 1534HV_0.1 and an adhesive strength of 55.4 MPa was made with appropriate spraying parameters.     

Enhancement of Functional Ceramic Coating Performance by Gas Tunnel Type Plasma Spraying

A high-precision plasma system has been pursued for advanced thermal processing. The gas tunnel type plasma jet device developed by the author exhibits high energy density and also high efficiency. Among its various applications is the plasma spraying of ceramics such as Al₂O₃ and ZrO₂. The performance of these ceramic coatings is superior to conventional ones. Properties such as the mechanical and chemical properties of the zirconia coatings were reported in previous studies. In this study, the enhancement of the performance of functional ceramic coatings by the gas tunnel type plasma spraying method was carried out using different powders. Results show that the alumina/zirconia composite system exhibited improvements of mechanical properties and corrosion resistance. The alumina/zirconia composite coating has the potential for use as a high functionally graded thermal barrier coating. Another application of the gas tunnel type plasma is for surface modification of metals. As an example, TiN films were formed in 5 s and, thick TiN coatings were easily obtained by gas tunnel type plasma reactive spraying.     

Microstructure and wear performance of gradient Ti/TiN metal matrix composite coating synthesized using a gas nitriding technology

Surface modification is an attractive method to enhance the surface hardness and wear resistance of titanium. In this paper, a continuous wave 2 kW Nd:YAG laser was used to synthesize Ti/TiN metal matrix composite coating on the surface of commercial pure titanium. The microstructure and the wear resistance of the synthesized metal matrix composite coating were investigated. The synthesized surface Ti/TiN metal matrix composite coating had a pronounced gradient microstructure through the melt depth. Good metallurgical bonding between the reinforcing phase of the metal matrix composite and the titanium matrix was observed. The hardness and wear resistance under block-on-ring dry sliding wear testing conditions of the synthesized Ti/TiN metal matrix composite coating were markedly enhanced.     

Surface nitridation of titanium metal by means of a gas tunnel type plasma jet

The surface nitridation of titanium was carried out at a low pressure in nitrogen atmosphere using a gas tunnel type plasma jet. The titanium nitride (TiN) film, 10 μm thick and 2000 HV, could be formed in 10 s. The structure of the TiN film was investigated by XRD. The Vickers hardness on the surface of the film was measured. The effects of deposition conditions on the properties of TiN films (TiN thickness,Vickers hardness, etc.) were investigated, and the advantage of this deposition method was identified from those results.     

Mechanical properties and oxidation resistance of chemically vapor deposited TiSiN nanocomposite coating with thermodynamically designed compositions

TiSiN coating with nanocrystallite surrounded by amorphous phase has attracted a broad interest because of its high hardness and excellent oxidation resistance desired for cutting tools. In the present work, TiSiN coatings were designed and prepared from a gaseous mixture of TiCl₄, SiCl₄, NH₃ and H₂ by low pressure chemical vapor deposition (CVD) process under the guidance of calculated CVD phase diagrams. The calculated compositions and phases in the deposited coatings agree well with the experimental ones. The deposited TiSiN coatings consist of nano-crystalline TiN and amorphous Si₃N₄ (a-Si₃N₄). A maximum hardness of about 2800 HV_0.02 was obtained, corresponding to a minimum crystallite size of 17.7 nm and a-Si₃N₄ volume fraction of 13.3% for TiSiN coating deposited at 1123 K under 3.0 kPa. After oxidation at 973 K for 1 h, TiSiN coating kept intact while TiN was completely oxidized. TiSiN nanocomposite coating formed by Si incorporation to TiN displayed superior hardness and oxidation resistance in comparison with those of TiN. The correlation of TiSiN coating hardness with volume fraction of a-Si₃N₄ and TiN grain size was discussed. The present work demonstrates a novel strategy of thermodynamic calculations and key experiments to deposit CVD TiSiN coatings highly efficiently, which is equally valid for the design of other CVD hard coatings.     

Phase constituents and mechanical properties of laser in-situ synthesized TiCN/TiN composite coating on Ti-6Al-4V

Laser in-situ synthesis technology at room temperature was applied to obtain TiCN/TiN composite coating. A pulsed Nd:YAG laser (wavelength 1064 nm) was used to melt the mixture of Ti and C powder. Pure nitrogen gas with a pressure of 0.4 MPa was introduced coaxially together with laser beam to the melting pool to react with Ti and C atoms and in-situ synthesize TiCN/TiN composite coating. The coating consists of TiC_0.3N_0.7, TiN and TiN_0.3, but the proportions of these three constituents vary with the laser power density. SEM results revealed that dendrites were oriented in accordance with the heat flow and a metallurgical bonding between the coating and the substrate was achieved. The in-situ synthesized TiCN/TiN composite coating, with a thickness of about 200 μm, increased the hardness and wear resistance compared to the bare Ti-6Al-4V substrate. A remarkable improvement of the average microhardness (3-4 times) and an enhancement of the wear resistance (10-11 times) are observed by laser in-situ synthesizing TiCN/TiN composite coating.     

超音速等离子喷涂Mo-W涂层的力学性能

采用超音速等离子喷涂技术在45CrNiMoVA钢表面制备了Mo-W合金涂层,利用场发射扫描显微镜(SEM)、电子能谱仪(EDS)、维氏显微硬度计分析测试了涂层组织、硬度,利用球-盘式摩擦磨损试验机研究了磨损载荷及频率对Mo-W合金涂层摩擦学性能的影响。结果表明:质量比为3:1的Mo、W机械混合粉喷涂后涂层中Mo、W元素质量比接近3:1。涂层组织致密,与基体结合为机械结合,表面平均显微硬度为563.2 HV0.1。Mo-W涂层的显微硬度、耐磨性和减摩性比基体45CrNiMoVA钢有所提高,且载荷越大,涂层的耐磨性和减摩性优势越明显。Mo-W涂层与Si3N4陶瓷的摩擦磨损机制以磨料磨损和氧化磨损为主。当磨损载荷变大和磨损频率变高时,疲劳剥落磨损表现明显。     

Synthesis and high-temperature stability of titanium aluminide matrixin situ composites

A premixture of elemental powders of titanium and aluminum was supplied as a spray material for the direct fabrication of titanium aluminide matrixin situ composites by means of reactive low-pressure plasma spraying with a nitrogen and hydrogen mixed plasma gas. The aluminum content varied from 10 to 63 wt.% in the premixtures. The matrix of sprayed layers consisted of three kinds of titanium aluminides—Ti₃A1, TiAl, and TiAl₃—which begin to form on a low-carbon steel substrate immediately after deposition. The formation of nitrides, which act as a reinforcement, occurs both during the flight of liquid droplets and on the substrate. The nitrogen content is approximately 4 to 5 wt.% in the sprayed intermetallic matrix composites, regardless of the aluminum content of the premixtures. The kinds of titanium aluminides andin situ nitrides developed depend on the aluminum content of the premixtures. The homogeneity of the distribution of aluminum and titanium in sprayed intermetallic matrix composites has been improved by vacuum annealing. The predominant TiAl phase that formed in the sprayed intermetallic matrix composites with a Ti-36 wt.% AI premixture increases in quantity through annealing. Although some minor nitrides disappear through annealing, the principal reinforcement, Ti₂AlN, does not decompose, but increases in quantity. The hardness of sprayed intermetallic matrix composites varies with aluminum content of the premixtures, but is always greater than that of sprayed titanium aluminides containing no nitrides. Annealing does not reduce the hardness of sprayed intermetallic matrix composites. Sprayed and annealed intermetallic matrix composites with a Ti-36 wt.% Al premixture maintain their hardness of approximately 500 HV up to 800 K. Hence, reactive low-pressure plasma spraying offers a promising fabrication method for titanium aluminide matrixin situ composites, which are expected to excel in wear resistance applications at elevated temperatures.     

DLC、TiN涂层对TC4钛合金抗砂尘冲蚀性能的影响

为提高TC4钛合金的抗砂尘冲蚀性能,采用金属蒸汽真空弧(MEVVA)离子源注入与磁过滤真空阴极弧(FCVA)沉积复合技术、磁控溅射技术在TC4钛合金表面制备DLC、TiN涂层。采用SEM、Raman、XRD、纳米压痕仪和划痕仪等方法对涂层的物相结构、硬度、弹性模量以及与基体的结合力进行表征。在冲蚀试验平台上考核试样在不同入射角度条件下的抗砂尘冲蚀性能。结果表明:DLC涂层表面结构致密,含有大量sp3键,硬度为62.1 GPa,弹性模量为391.64 GPa,结合力达80.4 N;TiN涂层表面存在许多熔滴颗粒及空穴,硬度为22.72 GPa,弹性模量为383.18 GPa,结合力达34.7 N。30°冲蚀条件下,涂层主要是通过提高基体表面硬度来抵抗砂尘粒子的微切削作用,从而提高TC4钛合金的抗砂尘冲蚀性能。90°冲蚀条件下,涂层通过延缓基体的塑性变形来实现TC4钛合金抗砂尘冲蚀性能的提高。     

基于响应曲面的Ar气氛超音速等离子喷涂钛涂层

采用超音速等离子喷涂可低成本、高效率制备钛涂层。采用响应曲面法（RSM）中的Box-Behnken（BBD）设计分析了Ar流量、功率、喷涂距离3个因素与超音速等离子射流中钛粒子飞行速度和温度的交互性,利用SEM和显微硬度计研究了钛涂层的微观结构和显微硬度。结果表明：建立的线性模型可靠,喷涂距离对粒子飞行速度和温度影响最大,且随喷涂距离增加粒子飞行速度减小温度增加,而Ar流量和功率对粒子飞行速度和温度的影响与喷涂距离相反。超音速等离子喷涂制备出的钛涂层硬度较低,且呈多孔结构,随粒子飞行速度增加孔隙率降低。     

Characterization and blood compatibility of TiCxN1 − x hard coating prepared by plasma electrolytic carbonitriding

A novel technique to form Ti(C, N) on titanium, named as plasma electrolytic carbonitriding (PEC/N) on cathode was successful used to prepare TiC_xN_1 − x coating. The structure, composition and morphology of the coating were characterized by XRD, XPS and SEM, respectively. The results indicated that TiC_0.3N_0.7 as a new species appears on the surface of the titanium plate, and the thickness of the coating with porous surface morphology increases with the treated time. The blood compatibility of the TiC_0.3N_0.7 coating was evaluated by haemolysis ratios, dynamic blood clotting test, plasma recalcification time and platelet adhesion. The results indicated that the blood compatibility of the plasma-treated titanium with TiC_xN_1 − x coating is significantly improved as compared to the original titanium. Additionally, the results derived from measurements of hardness and corrosion indicated that the coating has excellent mechanical and corrosion-resistant properties.     

Microstructure and tribological properties of Fe-Mo alloy-coated steel specimens prepared by low-pressure plasma spraying

Fe₇Mo₆-based alloy powder was low-pressure plasma sprayed on SS400 steel substrates, and the microstructure, hardness and tribological properties of the prepared substrates were investigated. Metastable BCC-coated and FeMo-coated steel specimens were obtained by low-pressure plasma spraying. The BCC-type Fe-42at% Mo alloy was stable at temperatures below 955 K. In addition, the BCC-type Fe-42at% Mo alloy coating layer exhibited micro-Vickers hardness as high as the FeMo coating layer. The metastable BCC-coated and FeMo-coated steel disk specimens exhibited friction coefficients as low as Fe₇Mo₆-based alloy specimens prepared by spark plasma sintering. Moreover, the specific wear rates of the FeMo/ASTM 52100 steel tribopairs were almost the same as those of the Fe₇Mo₆-based alloy/ASTM 52100 steel tribopairs.     

超音速等离子喷涂工艺参数对 Cr2O3涂层硬度的影响

目的研究影响超音速等离子喷涂Cr2O3涂层硬度的主要因素,制备出高硬度涂层。方法首先采用单变量法研究超音速等离子生成气体压力(空气压力)和喷涂距离对涂层显微结构的影响,然后采用正交试验研究喷涂电流、空气压力、喷涂距离对Cr2O3涂层硬度的影响。结果工艺参数对Cr2O3涂层硬度影响的主次顺序为:空气压力>喷涂电流>喷涂距离。结论获得高硬度涂层的最佳工艺参数组合为:空气压力0.4 MPa,喷涂电流270 A,喷涂距离200 mm。在该工艺条件下获得的涂层致密、均匀,孔隙率小。     

反应等离子喷涂 TiN 涂层的研究进展

TiN具有硬度高、韧性好、摩擦系数小、化学性能稳定等优点,广泛应用于刀具、装饰、表面防护等领域。目前制备TiN涂层的方法有很多,如气相沉积、热喷涂、电镀等,反应等离子喷涂则是最常用的金属-陶瓷复合涂层制备方法。概述了反应等离子喷涂技术的基本原理和分类,包括反应等离子喷涂涂层的形成过程及工艺的优缺点。综述了反应等离子喷涂TiN涂层的喷涂工艺及性能的研究进展,包括涂层的制备方法(原位合成法、烧结破碎法)和性能特点,重点分析了涂层的力学性能、耐磨损性能、耐腐蚀性能,并提出了可以依靠热处理工艺或封孔技术来提高涂层的耐腐蚀性能。依据实验和查阅的文献,反应等离子喷涂结合了自蔓延高温合成技术和等离子喷涂技术,可以制备质量优良的厚TiN涂层(500μm),是一种新型的低成本涂层制备技术,但是反应等离子喷涂制备TiN涂层存在孔隙率较高(5%~10%)、结合强度较低(50 MPa)的问题。分别从技术、设备、工艺、后处理四个方面总结了改善涂层质量的相应措施,展望了今后的研究发展方向。