Effect of RE element Y on properties of Ti(C, N)-based cermet

The effect of RE element Y on the microstructure and properties of Ti(C, N)-based cermet has been investigated. Yttrium can refine the particles of carbide phase because it can purify the interface between binder phase and carbide phase, and increase the thickness of rim phase slightly. The effect is in the most evidence when the mass fraction of Y is 0.8% and when the transverse rupture strength and the hardness of Ti(C, N)-based cermet are maximal.     

纳米Ti(C,N)增强Ti(C,N)基金属陶瓷的研究

采用纳米Ti(C,N)粉末制备Ti(C,N)基金属陶瓷,研究了纳米粉末对金属陶瓷组织及性能的影响。结果表明,粉末冶金过程中,纳米Ti(C,N)粉末易于在粘结相中扩散与溶解及沿晶界分布,降低了硬质相在粘结相中的溶解度,抑制了晶粒长大,提高了材料的红硬性能。抗弯强度与晶粒尺寸满足于Hall-Perch公式,5wt％～l0wt％的纳米粉末加入量可使金属陶瓷的抗弯强度和切削性能得到较大的提高,但硬度变化不大。切削磨损主要表现为磨粒磨损和轻微的粘着磨损,磨痕细小均匀。     

Corrosion and Electrochemical Behavior of β-W CVD Coatings in NaCl Solution

Protection of Metals and Physical Chemistry of Surfaces - The paper presents the results of a study of the corrosion-electrochemical behavior of coatings based on the metastable phase of tungsten...     

Corrosion behavior of thermal-sprayed WC cermet coatings in SO4 2− environment

A series of the electrochemical and long-term corrosion tests was carried out in a 3.5 wt% Na2SO4 solution on thermal-sprayed WC-17Co and WC-10Co-4Cr cermet coatings in order to examine the effect of composition of binder materials on the corrosion behavior. The results reveal that the overall corrosion resistance of the WC-17Co coating is inferior to that of the WC–Co–Cr coatings due to the corrosion of binder materials which induce WC particles to fall off. CoO and WO3 oxide films form on the surface of WC-17Co coating in Na2SO4 solution electrochemical corrosion process, which will protect the coating in the process of corrosion. Cr2O3 oxide film formed on the WC-10Co-4Cr coating surface has a strong hindered role to corrosion. The corrosion mechanism of WC-17Co coating in Na2SO4 solution is entire corrosion of Co matrix, while it is film-hole corrosion mechanism for WC-10Co-4Cr coating.     

Corrosion properties of anodic oxide coatings on Ti–6Al–4V in simulated body solution

Abstract

Anodic oxide coatings were synthesised on Ti–6Al–4V substrates using aqueous electrolytes containing dissolved calcium and phosphorus. Different coatings were produced by varying the time of synthesis. Inherent features of the coatings were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Uniform corrosion, electrochemical polarisation and ac impedance tests were performed in simulated body fluid (SBF). Small amounts of calcium and phosphorus are deposited from the electrolyte on to the coating and their levels increase with increasing duration of synthesis. Maximum values of porosity and thickness are obtained for oxides coated for 3 h. Coatings produced from shorter times showed very good resistance to the attack of SBF.     

Electrochemical behavior of organic and inorganic zinc-rich coatings in 3.5% NaCl solution

1　INTRODUCTIONZinc richcoatings (ZRP)havebeenusedformanyyearsinordertoprotectsteeleffectivelyinag gressiveatmospheres ,mainlyinmarineandindustrialenvironments,againstcorrosion .ItiscommonlyacceptedthattwofundamentalprotectionmechanismsoperateinZRP[13] :1)thegalvanicprotectionstage ,whichrequires goodelectricalcontactamongthezincparticlesthemselvesaswellasbetweenthemandthesteelsubstrate ;2 )thebarrier likebehaviorstage ,whichisreinforcedbytheamountandnatureofzinccorrosionproductslead ing…     

An investigation of the corrosion behaviour of a FeNiCoAlTa shape memory alloy in 3.5 wt-% NaCl solution

In this study, the corrosion behaviour of an FeNiCoAlTa (NCAT) shape memory alloy in 3.5% (w?w^?1) NaCl solution was evaluated. Linear polarisation resistance and potentiodynamic polarisation tests were conducted at 25°C. An open circuit potential (OCP) of ?381?mV (vs. saturated calomel reference electrode) and a corrosion rate (CR) of 0.0174?mm?y^?1 were obtained. The NCAT alloy did not show any passivation in the 3.5% (w?w^?1) NaCl solution. Its corrosion behaviour was very similar to that of G10180 (AISI 1018) carbon steel with the NCAT showing a lower CR and a less active OCP. Its corrosion in the solution was a combination of general dissolution and localised attack (pitting). Aging heat treatment caused β-Ni₃Al phase, and tantalum to precipitate on the grain boundaries, resulting in chemical species segregation between the grain boundaries and the grains. The chemical segregation caused intergranular corrosion of the alloy.     

Ti(C,N)_w/Ti(C,N)基金属陶瓷的组织与力学性能研究

采用Ti(C,N)晶须和颗粒复合粉末(Ti(C,N)w+Ti(C,N)p)制备Ti(C,N)w/Ti(C,N)基金属陶瓷。研究了复合粉末对金属陶瓷组织及性能的影响。结果表明,Ti(C,N)w的加入,金属陶瓷的各项力学性能都得到了提高。组织表现为环形相结构特征,与Ti(C,N)基金属陶瓷相比,双层环形相结构所占比例增大,且尺寸加厚。烧结组织中Ti(C,N)w的长径比大于临界长径比,在强化金属陶瓷方面起着重要的作用。环形相使Ti(C,N)w与基体界面结合紧密,增韧机制主要表现为裂纹桥联和裂纹偏转,拔出效应不明显。     

Ti(C,N)金属陶瓷中的添加剂

本文就添加剂对Ti（C，N）金属陶瓷机械性能的影响及其在Ti（C，N）金属陶瓷中的分布作了详细的阐述，并就Ti（C，N）金属陶瓷作模具材料的可能性进行了讨论。     

Corrosion and electrochemical behavior of Mg–Y alloys in 3.5% NaCl solution

The corrosion mechanism of Mg–Y alloys in 3.5% NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion potential of Mg–Y alloys in 3.5% NaCl solution increased with the increase of Y addition. The corrosion rate increased with the increase of Y addition because of the increase of Mg₂₄Y₅ intermetallic amounts. The corrosion gradually deteriorated with the increase of immersion time. The corrosion morphologies of the alloys were general corrosion for Mg–0.25Y and pitting corrosion for Mg–8Y and Mg–15Y, respectively. The main solid corrosion products were Mg(OH)₂ and Mg₂(OH)₃C1.4H₂O.     

A comparative study of microstructure,oxidation resistance,mechanical, and tribological properties of coatings in Mo–B–(N), Cr–B–(N) and Ti–B–(N) systems

M–B–(N) (M = Mo, Cr, Ti) coatings were obtained by the magnetron sputtering of MoB, CrB₂, TiB, and TiB₂ targets in argon and in gaseous mixtures of argon with nitrogen. The structure and composition of the coatings have been investigated using scanning electron microscopy, glow-discharge optical emission spectroscopy, and X-ray diffraction. The mechanical and tribological properties of the coatings have been determined by nanoindentation, scratch-testing, and ball-on-disk tribological tests. The experiments on estimating the oxidation resistance of coatings were carried out in a temperature range of 600–1000°С. A distinctive feature of TiB₂ coatings was their high hardness (61 GPa). The Cr–B–(N) coatings had high maximum oxidation resistance (900°С (CrB₂) and 1000°С (Cr–B–N)) and possessed high resistance to the diffusion of elements from the metallic substrate up to a temperature of 1000°С. The Mo–B–N coatings were significantly inferior to the Ti–B–(N) and Cr–B–(N) coatings in their mechanical properties and oxidation resistance, as well as had а tendency to oxidize in air atmosphere after long exposure at room temperature. All of the coatings with nitrogen possessed a low coefficient of friction (in a range of 0.3–0.5) and low relative wear ((0.8–1.2) × 10^–6 mm3 N^–1 m^–1.     

Microstructure and physical properties of PVD TiN/（Ti, Al）N multilayer coatings

Magnetron sputtered （Ti, Al） N monolayer and TiN/（Ti, Al） N multilayer coatings grown on cemented carbide substrates were studied by using energy dispersive X-ray spectroscopy （EDX）, scanning electron microscopy （SEM）, nanoindentation, Rockwell A indentation test, strength measurements and cutting tests. The results show that the （Ti, Al）N monolayer and TiN/（Ti, Al）N multilayer coatings perform good affinity to substrate, and the TiN/（Ti, Al）N multilayer coating exhibits higher hardness, higher toughness and better cutting performance compared with the （Ti, Al）N monolayer coating. Moreover, the strength measurement indicates that the physical vapour deposition （PVD） coating has no effect on the substrate strength.     

Wear and thermal behaviour of CVD α-Al2O3 and MTCVD Ti(C,N) coatings during machining

The wear properties of CVD α-Al₂O₃ layers with , and (0 0 0 1) growth textures were compared with MTCVD Ti(C,N) layers in single point turning of AISI 4140 steel. The experimental coatings were investigated with respect to thermal behaviour, deformation and wear. Substantial texture effects on wear performance of the α-Al₂O₃ layers were observed. A clearly enhanced ability of (0 0 0 1) textured layer to undergo uniform plastic deformation was confirmed. The Ti(C,N) layer exhibited a more uniform plastic deformation than the α-Al₂O₃ layers. The observations were interpreted in the light of thermal, mechanical and frictional conditions occurring at the tool-chip contact interface.     

Ti(C,N)固溶体的N/C原子比对Ti(C,N)基金属陶瓷组织及力学性能的影响

本文以不同N/C原子比的Ti(C,N)固溶体为硬质相,通过真空烧结制备了Ti(C,N)基金属陶瓷。用三点弯曲法、洛氏硬度计、压痕法分别测得试样的抗弯强度、硬度、断裂韧性,并通过光学金相显微镜、XRD、SEM、EDS等手段研究了Ti(C,N)固溶体的N/C原子比对Ti(C,N)基金属陶瓷组织的影响规律。结果表明:在一定范围内随着N/C原子比的增大,Ti(C,N)固溶体在液相中溶解度下降,环形相的析出受到抑制,使得金属陶瓷的硬质相芯部逐渐细化且分散均匀,环形相厚度减薄。但Ti(C,N)固溶体的N/C原子比为6∶4及以上时,硬质相与液相之间的润湿性较差,使得金属陶瓷孔隙度增加,显微组织中开始出现亮白色的晶粒。随N/C原子比的增大,金属陶瓷的抗弯强度和硬度先增大后降低,断裂韧性逐渐降低。当Ti(C,N)固溶体的N/C原子比为5∶5时,金属陶瓷的综合力学性能最佳,其抗弯强度为2 429 MPa,硬度为92.2 HRA,断裂韧性为8.44 MPa·m~(1/2)。     

(Ti,W,Ta)(C,N)_p/Ti(C,N)基金属陶瓷的组织与性能

采用自制的多元复式碳氮化物陶瓷粉末 ((Ti,W,Ta) (C,N) p)制备 (Ti,W,Ta) (C,N) p/Ti(C,N)基金属陶瓷。研究了 (Ti,W,Ta) (C,N) p 粉末的组织结构特征及其加入对金属陶瓷的组织及性能的影响。结果表明 ,多元复式碳氮化物粉末的晶格常数与元素的固溶度有很好的对应关系 ,调整粉末中元素的固溶度可控制粉末的晶格常数 ,进而控制材料的性能。 Ti(C,N)基金属陶瓷中 (Ti,W,Ta) (C,N) p 粉末的加入 ,有利于重金属元素 W和 Ta向粘结相中扩散 ,从而降低了硬质相在粘结相中的溶解度 ,阻碍了晶粒长大。(Ti,W,Ta) (C,N) p/Ti(C,N)基金属陶瓷各项性能指标优于 Ti(C,N)基金属陶瓷和国外对应的金属陶瓷牌号 CT5 2 5的产品。强化机制主要表现为细晶强化与固溶强化。     

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.     

Hot corrosion properties of composite coatings in the presence of NaCl at 700 and 900 °C

Cyclic hot corrosion tests have been carried out on three coatings (one NiCoCrAlY and two composite coatings) at 700 and 900 °C. The kinetic curves and evolution of microstructure show that the composite coating with a Cr-base interlayer performs best. The Cr₂O₃ scale is more effective to protect the coating at 700 °C than that at 900 °C. The corrosion process is accelerated by NaCl via forming volatile MCl_x and inducing the formation of molten voids in the coating or extra oxidation at the interface of fusant/oxide scale, determined by the temperature and the compositions of the coating.     

Ti(C,N)基金属陶瓷的耐腐蚀性

研究了Ti（C,N）基金属陶瓷在5％HNO3、50％NaOH溶液中的耐腐蚀性能,对比了金属陶瓷与YG8硬质合金在同种腐蚀介质中的耐蚀性优劣,并对金属陶瓷在5％HNO3溶液中的腐蚀形貌进行观察。试验结果表明：金属陶瓷有良好的耐酸碱腐蚀性能,其耐蚀性与粘结相的含量密切相关,粘结相的含量愈低,耐蚀性愈好;金属陶瓷的耐蚀性明显优于YG8硬质合金;金属陶瓷的腐蚀机理为钝化膜保护的电化学腐蚀。     

Ti(C,N)复合膜和TiN/Ti(C,N)多层膜组织和显微硬度

采用非平衡反应磁控溅射的方法在Si(100)基片上沉积Ti(C,N)复合膜和不同调制周期、调制比的TiN/Ti(C,N)纳米多层薄膜。薄膜的微观结构和力学性能采用X射线衍射仪(XRD)、显微硬度计进行表征。结果表明,Ti(C,N)复合膜的微观结构和力学性能与掺入C的含量有关;TiN/Ti(C,N)纳米多层膜的微观结构和力学性能与调制周期和调制比有关,其显微硬度在一定的调制周期和调制比范围内出现了超硬现象。Ti(C,N)、TiN/Ti(C,N)均为δ-NaCl面心立方结构;Ti(C,N)复合膜显微硬度提高是因为固溶强化,TiN/Ti(C,N)纳米多层膜硬度的提高主要是共格外延生长在界面处产生的交变应力场。     

Ti(C,N)基金属陶瓷增韧研究进展

Ti(C,N)基金属陶瓷作为一种新型工具材料,具有优良的耐磨性、高温红硬性、优良的化学稳定性以及金属间极低的摩擦系数的优点,同时全球钛储量是钨储量的1 000倍左右,是极佳的WC-Co硬质合金替代材料。但相比于HW类硬质合金,Ti(C,N)基金属陶瓷的强韧性低,如何提升其强韧性是开发高性能Ti(C,N)基金属陶瓷的技术瓶颈之一,也一直是全世界范围的一个研究热点。本文基于相转变法、显微裂纹法、裂纹偏转法、拔出法、裂纹桥接法、残余压力屏蔽效应等增韧手段,系统地综述了国内外Ti(C,N)基金属陶瓷增韧方面的研究进展,分析了Ti(C,N)基金属陶瓷增韧面临的问题并展望了未来金属陶瓷增韧的研究方向,以期为开发强韧性高、性能稳定的新型Ti(C,N)基金属陶瓷材料提供参考。