Deposition of thick TiAlN coatings on 2024 Al/SiCp substrate by Arc ion plating

Aluminum-matrix composites with particulate SiC ceramic reinforcements (Al/SiC_p) have received much attention for space and aircraft propulsion applications. It is imperative to deposit thick hard coatings on these composites for protection. TiAlN coatings with a Ti interlayer were deposited by arc ion plating (AIP) on 2024 Al/SiC_p substrates at various nitrogen flow rates. It was found that when the nitrogen flow rate is increased from 100 sccm to 250 sccm, the deposition rate decreases, the coating hardness increases and the adhesion strength decreases. Based on the above results and the principle of gradient materials, the thick gradient TiAlN coatings with a Ti interlayer were successfully deposited on a 2024 Al/SiC_p substrate to a thickness of 60 μm by continuously increasing the nitrogen flow rate during deposition. Such an achievement can be attributed to the gradient distribution of elements, hardness, and stresses across the coating thickness.     

Effect of C2H2 gas flow rate on synthesis and characteristics of Ti–Si–C–N coating by cathodic arc plasma evaporation

The influences of C₂H₂ gas flow rate on the synthesis, microstructure, and mechanical properties of the Ti–Si–C–N films were investigated. Quaternary Ti–Si–C–N coatings were deposited on WC-Co substrates using Ti and TiSi (80:20 at.%) alloy target on a dual cathodic arc plasma evaporation system. The Ti–Si–C–N coatings were designed with Ti/TiN/TiSiN as an interlayer to enhance the adhesion strength between the top coating and substrate. The Ti–Si–C–N coatings were deposited under the mixture flow of N₂ and C₂H₂. Composition analysis showed that as the C₂H₂ gas flow increased, the Ti, Si and N contents decreased and the carbon content increased in the coatings. The results showed the maximum nanohardness of approximately 40 GPa with a friction coefficient of 0.7 was obtained at the carbon content of 28 at.% (C₂H₂ = 15 sccm). However, as the C₂H₂ gas flow rate increased from 15 to 40 sccm (carbon content from 25.2 to 56.3 at.%), both the hardness and friction coefficient reduced to 20 GPa and 0.3, respectively. Raman analysis indicated the microstructure of the deposited coating transformed from Ti–Si–C–N film to TiSi-containing diamond-like carbon films structure, which was strongly influenced by the C₂H₂ flow rate and is demarcated at a C₂H₂ flow of 20 sccm. The TiSi-containing diamond-like carbon films reveal low-friction and wear-resistant nature with an average friction coefficient between 0.3 and 0.4, lower than both TiSiN and Ti–Si–C–N films.     

TiN, TiN gradient and Ti/TiN multi-layer protective coatings on Uranium

Single-layer TiN, gradient TiN and multi-layer Ti/TiN coating were deposited on silicon and uranium substrates by means of arc ion plating technique. The main phase in the single-layer TiN coating was TiN with a (111) preferred orientation. Ti and TiN were observed in the TiN gradient coating and Ti/TiN multi-layer coatings. The single-layer TiN coating has demonstrated the best wear resistance among the three coatings. Compared with the bare U substrate, the corrosion potential E_corr of the multi-layer Ti/TiN coatings is increased by 580 mV, and the corrosion current density I_corr is decreased at least by two orders of magnitude. The multi-layer Ti/TiN coatings possessed the highest corrosion resistance among the three coating in a 0.5 μg/g Cl⁻ solution.     

Characterization of nanocrystalline AlTiN coatings synthesized by a cathodic-arc deposition process

Graded and multilayered Al_xTi_1−xN nanocrystalline coatings were synthesized by using cathodic-arc evaporation (CAE) process. Ti₃₃Al₆₇ and Ti₅₀Al₅₀ alloy cathodes were used for the deposition of Al_xTi_1−xN nanocrystalline coatings with different Al/(Ti+Al) ratios. Optical emission spectra of the plasma species including atomic and ionized Ti, atomic Al, excited and ionized nitrogen (N₂ and N₂⁺) revealed that the excitation, ionization and charge transfer reactions of the Al-Ti-N plasma occurred during the Al_xTi_1−xN coating process. A preferred (111) orientation was shown in the Al_0.67Ti_0.33N with high Al/(Ti+Al) atomic content ratio (0.63) and small grain size (29 nm). The graded Al_0.67Ti_0.33N/TiN possessed the highest hardness of Hv_25 g 3850 ± 180. However, the multilayered Al_0.67Ti_0.33N/TiN coating supported a longer tool life with lower residual stress. It has been found that the wear performance and mechanical properties of the films were correlated with the Al/(Ti+Al) content ratio and multilayered structure.     

Effects of nitrogen content on structure and mechanical properties of multi-element (AlCrNbSiTiV)N coating

AlCrNbSiTiV metallic and nitride films were deposited by reactive radio-frequency unbalanced magnetron sputtering. The composition, microstructure and mechanical properties of the coatings deposited at different nitrogen flow rates were evaluated. The deposited AlCrNbSiTiV metallic film has an amorphous structure. The nitride films, regardless of the nitrogen flow ratio, were found to have only an FCC structure register on the XRD profiles. A Stoichiometric nitride ratio, i.e. (Al,Cr,Nb,Si,Ti,V)₅₀ N₅₀ is attained for a nitrogen flow ratio (R_N) of 10% and higher. At the lowest nitrogen flow ratio there is a preferred (200) orientation; however the films become less textured at higher nitrogen flow ratios. Nano-grained structures are obtained for all flow ratios, with grain sizes ranging from 8.7 to 12.3 nm. At the highest nitrogen flow rates the coatings have a compressive stress of around 4.5 GPa. The (Al,Cr,Nb,Si,Ti,V)₅₀ N₅₀ nitride coatings have both a high hardness and elastic modulus of 41 and 360 GPa, respectively. The maximum H/E ratio occurs at a nitrogen flow ratio of 20%.     

Hard and superhard TiAlBN coatings deposited by twin electron-beam evaporation

Superhard nanostructured coatings, prepared by plasma-assisted chemical vapour deposition (PACVD) and physical vapour deposition (PAPVD) techniques, such as vacuum arc evaporation and magnetron sputtering, are receiving increasing attention due to their potential applications for wear protection. In this study nanocomposite (TiAl)B_xN_y (0.09 ≤ x ≤ 1.35; 1.07 ≤ y ≤ 2.30) coatings, consisting of nanocrystalline (Ti,Al)N and amorphous BN, were deposited onto Si (100), AISI 316 stainless steel and AISI M2 tool steel substrates by co-evaporation of Ti and hot isostatically pressed (HIPped) Ti-Al-B-N material from a thermionically enhanced twin crucible electron-beam (EB) evaporation source in an Ar plasma at 450 °C. The coating stoichiometry, relative phase composition, nanostructure and mechanical properties were determined using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), in combination with nanoindentation measurements. Aluminium (∼ 10 at.% in coatings) was found to substitute for titanium in the cubic TiN based structure. (Ti,Al)B_0.14N_1.12 and (Ti,Al)B_0.45N_1.37 coatings with average (Ti,Al)N grain sizes of 5-6 nm and either ∼ 70, or ∼ 90, mol% (Ti,Al)N showed hardness and elastic modulus values of ∼ 40 and ∼ 340 GPa, respectively. (Ti,Al)B_0.14N_1.12 coatings retained their ‘as-deposited’ mechanical properties for more than 90 months at room temperature in air, comparing results gathered from eight different nanoindentation systems. During vacuum annealing, all coatings examined exhibited structural stability to temperatures in excess of 900 °C, and revealed a moderate, but significant, increase in hardness. For (Ti,Al)B_0.14N_1.12 coatings the hardness increased from ∼ 40 to ∼ 45 GPa.     

Structure-property relations in ZrCN coatings for tribological applications

ZrCN coatings were deposited by dc reactive magnetron sputtering with N₂ flows ranging from 2 to 10 sccm in order to investigate the influence of the nitrogen incorporation on structure and properties. Information about the chemical composition was obtained by glow discharge optical emission spectroscopy and Rutherford backscattering spectroscopy. The evolution of the crystal structure studied by X-ray diffraction revealed the formation of a face-centred cubic ZrCN phase for N₂ flows greater than 4 sccm. Additionally, the presence of an amorphous phase in the coatings deposited with the highest N₂ flows could be evidenced by Raman spectroscopy and X-ray photoelectron spectroscopy. This phase can act as a lubricant resulting in a low coefficient of friction as shown in the conducted ball-on-disc tests. Nanoindentation measurements showed that coatings deposited with a 6 sccm N₂ flow had the maximum hardness which also revealed the best performance in the conducted dry cutting tests.     

Cubic Aluminum Nitride Coating Through Atmospheric Reactive Plasma Nitriding

Aluminum nitride is a promising material for structural and functional applications. Cubic AlN (c-AlN) is expected to have higher thermal conductivity due to their high symmetry; however, its fabrication is difficult. In this study, c-AlN was synthesized by atmospheric plasma spray process through the reaction between Al feedstock powder and nitrogen plasma. Al powders were supplied to the plasma stream by Ar carrier gas and reacted with surrounding N₂ plasma, then deposit onto substrate. The obtained coatings were c-AlN/Al mixture at 150 mm of spray distance, and the nitride content was improved by increasing the spray distance. The coatings almost consist of c-AlN at 300 mm of spray distance. The coatings thickness decreased from 100 to 10 μm with increasing spray distance from 150 to 300 mm. Using carrier gas, N₂ enable to fabricate thick c-AlN coating with hardness 1020 Hv.     

CrN/CrAlSiN涂层海水环境下的摩擦学性能

为提高海洋装备摩擦零部件的摩擦学性能,采用多弧离子镀技术在316L不锈钢上制备了CrN/CrAlSiN涂层。通过XRD、XPS表征涂层的物相及成分,SEM和TEM表征涂层的形貌和微观结构,并用纳米压痕仪测试其硬度,采用摩擦磨损试验机对涂层在大气和海水环境中的摩擦磨损性能进行测试。结果表明:CrN/CrAlSiN涂层的微观结构主要有CrN相、AlN相以及非晶态Si_3N_4包裹CrN、AlN相,(111)择优取向最为明显;基于微观结构与CrN过渡层的设计,CrAlSiN涂层硬度高达35.5 GPa;较之于316L基底,涂层致密的结构使其在海水环境下表现出更好的耐腐蚀性能;在大气和海水环境下,CrN/CrAlSiN涂层的摩擦因数及磨损率均明显降低,在海水环境下达到最优。     

Relationship Between Crystalline Structure and Hardness of Ti-Si-N-O Coatings Fabricated by dc Sputtering

Ti-Si-N-O coatings were deposited on AISI D2 tool steel and silicon substrates by dc reactive magnetron co-sputtering using a target of Ti-Si with a constant area ratio of 0.2. The substrate temperature was 400 °C and reactive atmosphere of nitrogen and argon. For all samples, argon flow was maintained constant at 25 sccm, while the flow of the nitrogen was varied to analyze the structural changes related to chemical composition and resistivity. According to results obtained by x-ray diffraction and stoichiometry calculations by x-ray energy dispersive spectroscopy the Ti-Si-N-O coatings contain two solid solutions. The higher crystalline part corresponds to titanium oxynitrure. Hardness tests on the coatings were carried out using the indentation work model and the hardness value was determined. Finally, the values of hardness were corroborated by nanoindentation test, and values of Young’s modulus and elastic recovery were discussed. We concluded that F2TSN sample (F _Ar = 25 sccm, F _N = 5 sccm, P = 200 W, and P _W = 8.9 × 10⁻³ mbar) presented the greatest hardness and the lowest resistivity values, due to its preferential crystalline orientation.     

不同双层结构AlCrN/AlCrVN多层涂层的力学和磨损性能

采用电弧离子镀的方法制备了不同数目（1、2、4、6）双层结构的AlCrN/AlCrVN多层涂层,并研究了多层结构对涂层微观结构、力学、摩擦学和切削性能的影响。结果显示,沉积态AlCrN/AlCrVN多层涂层主要由固溶(Al,Cr)N组成,优先生长方向为[111]晶向。与其他多层涂层相比,具有6层双层结构的AlCrN/AlCrVN涂层在高温下表现出较低的摩擦系数（约0.46）和磨损率（0.15×10^-11 m³/N·m）,以及较高的硬度（HK_0.05=38 000 MPa）和膜-基结合强度（L_C2=53±1 N）。多层涂层相邻层之间形成了较多的界面,有助于提高多层涂层的硬度和耐磨性。切削试验结果显示,当切削磨损标准VB=0.2时,AlCrN/AlCrVN-6涂层具有较高的硬度和耐磨性,最长的切削长度为7.4 m。     

Tribological properties of titanium aluminides coatings produced on pure Ti by laser surface alloying

Titanium aluminides coatings were in-situ synthesized on a pure Ti substrate with a preplaced Al powder layer by laser surface alloying. The friction and wear properties of the titanium aluminides coatings at different normal loads and sliding speeds were investigated. It was found that the hardness of the titanium aluminides coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating. Friction and wear tests revealed that, at a given sliding speed of 0.10 m/s, the wear volume of pure Ti and the titanium aluminum coatings all increased with increasing normal load. At a given normal load of 2 N, for pure Ti, its wear volume increased with increasing sliding speed; for the titanium aluminides coatings, the wear volume of Ti₃Al coating and TiAl coating first increased and then decreased, while the wear volume of TiAl₃ coating first decreased and then increased with increasing sliding speed. In addition, the friction coefficients of pure Ti and the titanium aluminides coating decreased drastically with increasing sliding speed. Under the same dry sliding test conditions, the wear resistance of the titanium aluminium coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating.     

Gas phase aluminizing of TiAl intermetallics

The aim of this study was the microstructural characterization of aluminide diffusion coatings deposited on Ti48Al2Cr2Nb and Ti46Al7Nb alloys. The coatings' deposition process was prepared using out of pack method. The X-ray diffraction phase analysis from the surface of coatings indicated that TiAl₂ phase dominates in the coating. The thickness of aluminide coating was about 10 μm.     

Microstructure and properties of CVD coated Ti(C,N)-based cermets with varying WC additions

In this paper, multilayer coatings of TiN/TiCN/Al₂O₃/TiN are deposited on the Ti(C, N)-based cermets containing WC, and the effect of WC on the growth and adhesion strength as well as the mechanical properties of the coating are investigated. The multilayer coatings deposited by chemical vapor deposition (CVD) are uniform and dense. TiN coating exhibits a dense fine-grained structures and the Ti (C,N) on TiN coating shows dense columnar structure. The α-Al₂O₃ layer deposited on transition coating presents coarse grains with limited voids. The grain size of the columnar crystals deposited on the substrates gradually decreases with WC addition. The Al₂O₃ layer shows a preferred growth orientation of (104) plane. For TiN/TiCN phase, a change in orientation from (111) to (200) is observed. Generally, the (200) preferred orientation enhances and (111) preferred orientation diminishes with increasing WC addition. Strong adhesion of the CVD coating is obtained due to a sufficient amount of chemical elements, especially tungsten, diffusing from the substrate to the interfacial layer. Scratch tests show that the adhesion strength of TiN/TiCN/Al₂O₃/TiN films gradually increases firstly, and then decreases. With the addition of WC, the hardness, elastic modulus and plasticity index increase at the beginning, and then decrease. The change in nanohardness and elastic modulus is related to the grain size, elemental diffusion, and preferred orientation of the coating.     

Reactive Plasma Spraying of Fine Al2O3/AlN Feedstock Powder

Reactive plasma spraying (RPS) is a promising technology for in situ formation of aluminum nitride (AlN) coatings. Recently, AlN-based coatings were fabricated by RPS of alumina (Al₂O₃) powder in N₂/H₂ thermal plasma. This study investigated the feasibility of RPS of a fine Al₂O₃/AlN mixture and the influence of the plasma gases (N₂, H₂) on the nitriding conversion, and coating microstructure and properties. Thick AlN/Al₂O₃ coatings with high nitride content were successfully fabricated. The coatings consist of h-AlN, c-AlN, Al₅O₆N, γ-Al₂O₃, and a small amount of α-Al₂O₃. Use of fine particles enhanced the nitriding conversion and the melting tendency by increasing the surface area. Furthermore, the AlN additive improved the AlN content in the coatings. Increasing the N₂ gas flow rate improved the nitride content and complete crystal growth to the h-AlN phase, and enhanced the coating thickness. On the other hand, though the H₂ gas is required for plasma nitriding of the Al₂O₃ particles, increasing its flow rate decreased the nitride content and the coating thickness. Remarkable influence of the plasma gases on the coating composition, microstructure, and properties was observed during RPS of the fine particles.     

Al/Cr原子比对AlCrTiSiN多元复合刀具涂层微观结构及切削性能的影响

AlCrTiSiN多元复合涂层能显著改善刀具的表面特性,可大幅提高刀具的切削性能,延长刀具使用寿命。在高速钢样品和铣刀表面通过多弧离子镀制备AlCrTiSiN多元复合涂层,并研究了Al/Cr原子比对AlCrTiSiN多元复合涂层微观结构及切削性能的影响。采用X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、纳米压痕仪、划痕仪和球盘摩擦磨损试验对涂层的微观结构和力学性能进行研究,并通过切削试验对涂层刀具的寿命进行测试。研究结果表明:当Al/Cr比为0.4时,AlCrTiSiN涂层物相由fcc-AlCrN,fcc-Al Ti N,hcp-Al N和非晶态Si_3N_4相组成,涂层呈现(200)AlCrN择优取向;随Al/Cr比由0.4降低至0.2时,涂层物相由fcc-AlCrN,fcc-Al Ti N,hcp-Cr2N和非晶态Si_3N_4相组成,(200)AlCrN择优取向消失。随Al/Cr比由0.4降低至0.2时,AlCrTiSiN涂层硬度和结合力增加,摩擦因数和磨损率降低,与另两组相比,AlCrTiSiN-3涂层具有较好的抗摩擦磨损性能,其涂层刀具具有相对较高的切削寿命。     

Microstructure and mechanical properties of CrN coating deposited by arc ion plating on Ti6Al4V substrate

CrN coatings have been grown by arc ion plating (AIP) onto Ti6Al4V alloy substrate at various nitrogen pressures (PN₂). The goals of this investigation are to study the influence of nitrogen pressure content on the composition, structure and mechanical properties of AIP CrN coatings, as well as their tribological properties. With an increase of PN₂, the main phases in the coatings changed from CrN + Cr₂N + Cr to CrN, and the texture of CrN was transformed from CrN (111)-oriented to (220)-oriented. Furthermore, the multi-layers including a metal Cr layer, a Cr₂N layer and a CrN layer were observed by cross-sectional TEM (XTEM), besides an “unbalanced” state transition layer at the interface of CrN/substrate which was analyzed by nucleation thermodynamics subsequently. An increase in nitrogen pressure also resulted in a change of micro-hardness due to the variation in composition and structure. Finally, the tribological properties of the Ti6Al4V substrate and the CrN/Ti6Al4V coating system have also been explored, which shows that CrN coatings can act as good wear resistance layer for Ti6Al4V substrate.     

Structure and properties of selected (Cr–Al–N,TiC–C,Cr–B–N) nanostructured tribological coatings

The paper will present the state-of-art in the process, structure and properties of nanostructured multifunctional tribological coatings used in different industrial applications that require high hardness, toughness, wear resistance and thermal stability. The optimization of these coating systems by means of tailoring the structure (graded, superlattice and nanocomposite systems), composition optimization, and energetic ion bombardment from substrate bias voltage control to provide improved mechanical and tribological properties will be assessed for a range of coating systems, including nanocrystalline graded Cr_1−xAl_xN coatings, superlattice CrN/AlN coatings and nanocomposite Cr–B–N and TiC/a-C coatings. The results showed that the superlattice CrN/AlN coating exhibited a super hardness of 45 GPa when the bilayer period Λ was about 3.0 nm. Improved toughness and wear resistance have been achieved in the CrN/AlN multilayer and graded CrAlN coatings as compared to the homogeneous CrAlN coating. For the TiC/a-C coatings, increasing the substrate bias increased the hardness of TiC/a-C coatings up to 34 GPa (at −150 V) but also led to a decrease in the coating toughness and wear resistance. The TiC/a-C coating deposited at a −50 V bias voltage exhibited an optimized high hardness of 28 GPa, a low coefficient of friction of 0.19 and a wear rate of 2.37 × 10⁻⁷ mm³ N⁻¹ m⁻¹. The Cr–B–N coating system consists of nanocrystalline CrB₂ embedded in an amorphous BN phase when the N content is low. With an increase in the N content, a decrease in the CrB₂ phase and an increase in the amorphous BN phase were identified. The resulting structure changes led to both decreases in the hardness and wear resistance of Cr–B–N coatings.     

沉积偏压对AlCrTiN纳米复合涂层力学与抗高温氧化性能的影响

沉积偏压对涂层的结构与性能具有重要影响,为研究其对AlCrTiN纳米复合涂层成分、组织结构、力学与抗高温氧化性能的影响规律,采用磁控溅射技术,改变沉积偏压(-30、-60、-90、-120 V)制备四种AlCrTiN纳米复合涂层。利用X射线衍射仪、扫描电子显微镜、纳米压痕仪等仪器表征涂层的组织结构、成分、力学性能和抗高温氧化性能。研究结果表明：不同偏压下制备的AlCrTiN纳米复合涂层均为NaCl型fcc-(Al,Cr,Ti)N相结构。随着沉积偏压增大,涂层由沿(111)晶面择优生长转变为无明显的择优生长取向,晶粒尺寸降低,残余应力和硬度增大。偏压为-90 V与-120 V时,涂层表面更加致密,具有更高的硬度和弹性模量。在800℃与900℃氧化1 h后,所有涂层表面均生成一层连续致密的Al₂O₃膜。随着沉积偏压增加,氧化膜厚度逐渐降低,表明抗高温氧化性能逐渐增强,这是因为高偏压下涂层组织更致密,且晶粒更细小。研究成果对AlCrTiN纳米复合涂层的综合性能提升与工程化应用具有一定指导意义。     

Splat Morphology and Influence of Feeding Rate During Reactive Plasma Spray of Aluminum Powder

Fabrication of aluminum nitride (AlN) coatings using conventional plasma spraying processes directly has been deemed impossible. It is attributed to the thermal decomposition of the AlN feedstock particles during spraying without a stable melting phase. Using the reactivity of the plasma (reactive plasma spraying: RPS) showed a promising consideration for in situ formation of AlN thermally sprayed coatings. Several AlN-based coatings were fabricated through the RPS of aluminum powders in the N₂/H₂ plasma. The focus of this study is in discussing the morphology of splat deposition during the nitriding of Al particles. Furthermore, the influence of the feeding rate during the RPS and nitriding of Al powders will be investigated. The nitride content, as well as the unreacted molten Al phase, strongly influences splat deposition and morphology during the RPS of Al. The collected splats can be divided into reacted, partially reacted, and unreacted splats. The reacted splats tend to show a disk or egg-shell shape. The partially reacted mainly had outside nitride shells and an unreacted molten Al part in the center. The unreacted splats tended to show a splash shape. The main controlling factor is the time of the droplet impact on the substrate during the reaction sequence. The particle size and spray distance showed significant effects on the splat formation due to their effect on the nitriding conversion and the melting behavior of the particles during RPS nitriding. The powder feeding rate was investigated through increasing the injection rate and by using a low carrier gas flow rate. Increasing the powder feeding rate significantly improved the coating thickness. However, it suppressed the nitriding conversion of the large Al particles. Thus, with increasing the amount of the powder in the plasma, the Al molten particles are easily aggregated and agglomerate together upon colliding on the substrate with an AlN shell on the surface. This prevents the N₂ from having access to all of the aggregated particles. Therefore, the fabricated coatings using large Al particles consist of surface AlN layers and the central parts of AlN and Al composite layers. On the other hand, it was possible to fabricate about 500-μm-thick AlN coatings using fine Al particles of 15 μm and increasing the feeding rate. Using the fine particles improved the nitriding reaction due to the improvement of the surface area (the reaction area). Moreover, the nitriding process of the Al particles with increasing the feeding rate was also investigated.