钛铝基合金离子碳氮共渗及其耐磨性的研究

为提高TiAl基合金的耐磨性及抗高温氧化性,利用渗氮在TiAl基合金表面形成氮化物,以提高耐磨性;渗碳形成致密且与基体结合牢固的碳化物层,提高抗高温、抗氧化性;将二者结合,采用辉光离子碳氮共渗的方法,研究了渗层的相结构组成、不同工艺参数对TiAl基合金离子碳氮共渗后渗层厚度以及表面硬度和耐磨性的影响.结果表明:TiAl基合金共渗层是由碳氮化合物层与过渡层组成的复合相结构;随共渗温度的升高和时间的延长,渗层厚度增加;与未经共渗处理的试样相比,表面硬度及耐磨性显著提高.X射线衍射结果显示,渗层主要由TiC,TiN,AlTi3,Al2O3等组成.     

Microstructure and characterization of Ni-Co/Al2O3 composite coatings by pulse reversal electrodeposit

Ni-Co/Al₂O₃ composite coatings were obtained by pulse reversal electrodeposit (PRC) and direct current electrodeposit (DC). The microstructure of the coatings was characterized by means of SEM, XRD and TEM. Hardness, wear resistance and macro residual stress of coatings were also investigated. The results showed that the microstructure and performance of the coatings were significantly affected by the electrodeposit methods and the Al₂O₃ particles content. The PRC composite coatings exhibited compact surface, high hardness and excellent wear resistance. The macro residual stress of PRC composite coatings was lower than that of DC ones. With the increasing of Al₂O₃ particles content, the hardness and wear resistance of the composite coatings increased.     

Titanium nitride laser-beam surface-alloying treatment on carbon tool steel

In order to improve the wear resistance of tool steel, a study of TiN surface-alloying treatment on 1% carbon steel by irradiation with a CO₂ laser beam was performed. Argon and nitrogen were used as shielding gases, and their effects on the formation of the surface-alloyed layer were investigated. The effect of cobalt additions to the TiN powder on the hardness of the alloyed layer was also investigated. When argon was used as shielding gas, the depth of the alloyed layer was increased compared with the depth when nitrogen was used as a shielding gas. A portion of the TiN decomposed into titanium in the argon environment, the nitrogen apparently being lost as a gas. The structure of the surface-alloyed layer was composed of a ferritic phase without martensitic structure even at high cooling rates. When this layer was annealed at 1000 ° C for 3 h, part of the titanium precipitated as TiC particles. The hardness of the annealed alloyed layer increased to about 500 Hv. This increase in hardness was accompanied by the appearance of martensite. When nitrogen was used as shielding gas, decomposition of TiN was suppressed and the hardness of the alloyed layer reached 850 Hv. These layers had a martensitic structure. Thus, nitrogen is preferable to argon as a shielding gas if a martensitic structure is desired in this system. When 5% cobalt was added to the TiN powder, the hardness of the alloyed layer increased to 1100 Hv. This increased hardness is caused by stabilization of the martensitic structure caused by an increase in theM _s temperature.     

Fabrication and Characterization of FeNiCr Matrix-TiC Composite for Polishing CVD Diamond Film

Dynamic friction polishing (DFP) is one of the most promising methods appropriate for polishing CVD diamond film with high efficiency and low cost.By this method CVD diamond film is polished through being simply pressed against a metal disc rotating at a high speed utilizing the thermochemical reaction occurring as a result of dynamic friction between them in the atmosphere.However, the relatively soft materials such as stainless steel, cast iron and nickel alloy widely used for polishing CVD diamond film are easy to wear and adhere to diamond film surface, which may further lead to low efficiency and poor polishing quality.In this paper, FeNiCr matrix-TiC composite used as grinding wheel for polishing CVD diamond film was obtained by combination of mechanical alloying (MA) and spark plasma sintering (SPS).The process of ball milling,composition, density, hardness, high-temperature oxidation resistance and wear resistance of the sintered piece were analyzed.The results show that TiC was introduced in MA-SPS process and had good combination with FeNiCr matrix and even distribution in the matrix.The density of composite can be improved by mechanical alloying.The FeNiCr matrix-TiC composite obtained at 1273 K was found to be superior to at 1173 K sintering in hardness, high-temperature oxidation resistance and wearability.These properties are more favorable than SUS304 for the preparation of high-performance grinding wheel for polishing CVD diamond film.     

Cr2AlC复合材料的研究进展

Cr2AlC是一种可加工三元层状结构材料,兼具金属和陶瓷的优异性能。将Cr2AlC作为增强相与基体材料复合,可以有效地改善基体材料的综合性能,克服基体单一材料的部分缺点,扩大基体材料的应用范围。固溶强化和颗粒弥散增强Cr2AlC基复合材料相对于Cr2AlC单相材料,具有更高的硬度、耐磨性、强度和韧性,但损失了部分可加工性。Cr2AlC作为强化层与基体形成的层状复合材料,可以有效抑制微裂纹扩展,从而获得具有极高耐磨性的层状陶瓷复合材料。     

Verschleiß von TaC- und TiC-Laserdispersionsschichten durch weiche und harte Abrasivstoffe

Wear of TaC and TiC steel composite hardfacings by soft and hard abrasives TiC and TaC steel composite layers were produced on a die steel 90MnCrV8 (0.9% C) by using a CO₂-laser. The hard particles of it median size of 3 μm and 30 μm, respectively, and a volume fraction of about 50% were homogeneously distributed in the steel matrix. Hardness of the martensitie matrix was variied by heat treatments. Wear resistance of the hardfacings against flint and SiC with varying mesh sizes were measured using an abrasive wear tester at laboratory atmosphere. Abrasive wear resistance was increased by more than one magnitude of order by embedding the hard phases in the steel surface. The results showed the effects of type and size of the hard phase, hardness of the steel matrix and also of the type and mesh size of abrasive grits on wear resistance. Experimental results arc discussed as a function of those parameters and theoretical models arc developed.     

Effect of tempering temperatures on microstructures and properties of 0.28C–0.22Ti wear-resistant steel

The microstructures and properties of a 0.28C–0.22Ti low-alloy wear-resistant steel at different temperatures from 200 to 600°C was experimentally studied. It is shown that the wear resistance of the steel is not monotone changing with its hardness and strength. With the increase of the tempering temperature, the tensile strength and the hardness of the steels were gradually declined; however, the wear resistance was first decreased and then increased. The TiC particles can be divided into two classes: the small TiC particles (about 0.3–0.4?µm in diameter) and the coarse TiC particles (1–5?µm in diameter). The small TiC particles can improve the yield strength of the steels, and the coarse TiC particles can improve the wear resistance of the tested steels.     

热输入对金属基复合涂层中(Nb,Ti)C颗粒分布及性能的影响

目的 热输入对复合碳化物的析出、分布及耐磨性能具有重要影响。然而,目前热输入对碳化物增强金属基复合堆焊层组织结构与性能方面影响的研究较少。因此,需要探究焊接热输入对(Nb,Ti)C增强金属基复合堆焊层组织及耐磨性的影响,明确(Nb,Ti)C复合颗粒在堆焊层的作用机制。方法 采用Ar保护气体进行堆焊涂层的制备,通过调节堆焊电流和电压,研究不同热输入下堆焊层的形貌、组织及耐磨性能。结果 堆焊层中Ti元素与C元素优先发生了原位反应,生成了以TiC为形核中心的(Nb,Ti)C复合碳化物,弥散分布在马氏体基体组织上。随着热输入的增大,析出的(Nb,Ti)C颗粒数量逐渐减少,块状(Nb,Ti)C尺寸也逐渐变小。采用较低的热输入时,堆焊层硬度达到最高,为734.88HV0.5;随着堆焊热输入的增大,堆焊层的显微硬度呈降低趋势。具有较多(Nb,Ti)C的低热输入试样耐磨性能最佳,磨损量为0.80 mg;而具有较少(Nb,Ti)C的高热输入试样产生了严重的黏着磨损,磨损量较低热输入试样增大了约144%。结论 在摩擦磨损过程中,高硬度的(Nb,Ti)C颗粒会对基体起保护作用,可以提升其耐磨性能,且耐磨损性...     

钛合金表面Nb-C复合渗层摩擦磨损性能的研究

为提高钛合金表面的耐磨性能,采用等离子表面合金化技术在Ti6A14V(TC4)合金表面形成含Nb的梯度改性层,然后进行渗C复合处理,得到Nb-C复合改性层,研究了改性层的显微组织形貌、成分分布、相结构特征及硬度分布,并进行了球盘摩擦磨损实验.结果表明,Nb、C元素呈梯度分布,合金层主要由Ti、TiC、Nb2C、NbC等...     

大尺寸硬质合金部件的燃烧合成研究

采用自蔓延高温燃烧合成结合准热等静压技术（SHS／PHIP）,成功地得到了致密性良好,直径为240mm的大尺寸TiC-Ni系硬质合金部件,燃烧合成产物由TiC和Ni两相组成,Ni粘结相基本上呈网状连续分布于球形的TiC颗粒周围,随着Ｎi含量的增加,ＴiC颗粒尺寸减小,燃烧合成产物具有良好的力学性能。     

粉末冶金制备工艺对TiC增强高铬铸铁基复合材料性能的影响EI北大核心CSCD

采用高能球磨和真空烧结的方法制备TiC增强高铬铸铁(HCCI)基复合材料。利用SEM,DSC等方法对不同球磨时间的粉末进行分析,研究不同烧结温度对高铬铸铁基复合材料的显微组织、硬度及密度的影响,比较相同工艺下复合材料与高铬铸铁材料的耐磨性。结果表明:球磨12 h后的粉末颗粒大小趋于稳定,粉末活性提高,烧结性能改善,烧结试样中TiC均匀地分布在基体中。随着烧结温度的升高,复合材料内部晶粒逐渐长大,密度和硬度逐渐提高。在1280℃超固相线液相烧结的条件下烧结2 h后,致密度达94.17%,硬度和抗弯强度分别为49.2HRC和980 MPa。在销盘磨损实验中复合材料的耐磨性为单一高铬铸铁材料的1.52倍,磨损机制为磨粒磨损+轻微氧化磨损。     

Analysis of coating interlayer between silicon nitride cutting tools and titanium carbide and titanium nitride coatings

Silicon nitride (Si₃N₄) cutting tools exhibit excellent thermal stability and wear resistance in the high-speed machining of cast irons, but show poor chemical wear resistance in the machining of steel. Conventional chemical vapour deposition (CVD) coating of Si₃N₄ tools has not been very successful because of thermal expansion mismatch between coatings and the substrate. This problem was overcome by developing a CVD process to tailor the interface for titanium carbide (TiC) and titanium nitride (TiN) coatings. Computer modelling of the CVD process was done to predict which phases would form at the interface, and the results compared with analyses of the interface. Three Si₃N₄ compositions were considered, including pure Si₃N₄, Si₃N₄ with a glass phase binder, and Si₃N₄ + TiC composite with a glass phase binder. Results of machining tests on coated tools show that the formation of an interlayer provides superior wear resistance and tool life in the machining of steel as compared to uncoated and conventionally coated Si₃N₄ tools.     

Microstructure,mechanical properties,electrical conductivity and wear behavior of high volume TiC reinforced Cu-matrix composites

This study deals with the processing, microstructure, mechanical properties, electrical conductivity and wear behavior of high volume titanium carbide reinforced copper matrix composites. The microstructural study revealed that the titanium carbide particles were distributed uniformly in the matrix phase. No interface debonding and micro-cracks were observed in the composite. The addition of alloying elements in the copper considerably increased the sintered density and properties. The composite hardness and strength increased with titanium carbide content and alloying elements in the matrix phase. The electrical conductivities of the composites were predicted using three point upper bound and two phase self consistent predictive models. The wear resistance of the composites was studied against high speed steel. Wear mechanisms were discussed by means of microscope observations on the worn surfaces. The ratio of titanium carbide average grain size to the mean free path of the binder was introduced as a parameter to determine wear performance.     

Characterization of wurtzitic boron nitride compacts

Characterization of sintered polycrystalline wurtzitic boron nitride compacts was carried out regarding the different crystalline phases that are formed at high temperature and high pressure, composition, particle size distribution of BN and binder and hardness. Wurtzitic boron nitride, cubic boron nitride, TiC/TiN solid solution, TiB and TiB₂ were the crystalline phases that have been observed in sintered wurtzitic boron nitride compacts. The particle size distribution of BN and the binder was found to be comparable (1 to 5m), with about 80% of the particles lying between 2 and 3m. Weight percentages of different elements present in these compacts were determined. The average Knoop hardness values under 500 g load were measured, and the variation of hardness as a function of position on the specimen surface was studied.     

Schwingungsverschleiß an TiB2-ZrO2 und TiC-ZrO2 oberflächenlegierter Al2O3-Keramik unter Variation der Luftfeuchte

Oscillating sliding wear of TiB₂-ZrO₂ and TiC-ZrO₂ surface alloyed Al₂O₃ ceramic at different humidity A commerical alumina ceramic was surface-alloyed by adding TiB₂ and TiC in addition to ZrO₂ using infrared CO₂ laser radiation. Aside from the type of hard particles their volume fraction was varied between 6 and 31%. The average thickness of the alloyed surface layer was about 150 ¨?m. Tribological tests were carried out unlubricated under oscillating sliding contact against alumina counterbodies at relative humidities of 3 and 50% as well as in distilled water. Ceramographic studies showed that multiphase structures containing hard particles of TiC or TiB₂ embedded in the Al₂O₃ matrix were obtained by alloying. In addition Al-Zr-Ti-O complex phases were analyzed by using X-ray diffraction technique. Compared to the commercially available alumina ceramic A123, laser alloying reduced the friction coefficient and improved substantially the wear resistance under the applied conditions of tribological testing. It was found that tribological behaviour was strongly influenced by environmental humidity in addition to the effect of the type and volume fraction of the phases produced by alloying. The unalloyed alumina ceramic depended more sensitively on humidity than the alloyed ceramic.     

Si、Ti、Mo添加剂对自蔓延防护涂层性能的影响

为了提升自蔓延涂层的各项性能,拓宽自蔓延涂层的应用领域,本文实验制备了两种自蔓延防护涂层,即Al和Fe₂O₃的自蔓延铝热涂层和含有Si、Ti、Mo添加剂的低温自蔓延铝热涂层,借助X射线衍射、扫描电子显微镜等技术对不同成分涂层的组织形貌和物相组成进行了对比分析。利用显微硬度计、万能实验机、多功能摩擦磨损试验机研究了两种涂层的力学性能和摩擦性能。研究表明,添加剂使得涂层的孔隙率降低了66.7%,结合强度提高32.3%,常温下显微硬度提高17.6%,断裂韧性提高了28%,耐磨性能提高约25%。两种涂层均呈现出以Al₂O₃相为主的陶瓷层、金属过渡层与基体的3层结构,Si、Ti、Mo添加剂使得涂层中出现了SiC、TiC、MoSi₂等硬质相,且反应更为充分,结合强度、硬度、断裂韧性、摩擦性能均得到提升。     

Ni基WC合金3D激光熔覆工艺研究

以正交实验规则设计3D激光熔覆试验来研究不同工艺参数对熔覆指标的影响,实验表明,WC添加量对熔覆层硬度、抗磨性影响最大,激光功率影响稍次之,激光扫描速度影响次之,送粉速度影响最小。对熔覆层组织分析表明,随WC添加量增多,更易生成CrB、W2B等硬质相,未分解的WC颗粒也越多,粘结相Ni枝晶越细小。激光熔覆Ni基WC合金涂层表面摩擦磨损特性表现为以磨粒磨损为主,塑性变形、粘着磨损和磨粒磨损相结合。     

感应熔覆原位自生TiC/Ni基复合涂层的组织与耐磨性研究

为了提高16Mn钢的干滑动磨损耐磨性能,以Ni60、钛粉和石墨粉为原料对16Mn钢表面进行感应熔敷处理,制备出以TiC颗粒为增强相的原位自生复合涂层,利用金相、SEM、XRD等技术分析了涂层的显微组织,在室温干滑动磨损试验条件下测试了涂层的耐磨性.结果表明:涂层中TiC颗粒均匀分布于共晶基体上,整个涂层组织均匀、无气孔、无裂纹;涂层与基材形成了良好的冶金结合,涂层具有很高的硬度,在室温干滑动磨损试验条件下具有优异的耐磨性能.     

Effect of carbon content of substrate on alloying layer in double glow plasma surface alloying

Surface age-hardening high-speed steel has been formed on the surface of different substrates by double glow plasma surface alloying (DGPSA) technique, which possesses many excellent properties such as high hardness, high anti-temper stability, high wear resistance, etc. The hardness of the surface alloying layer is mainly determined by the construction of alloying layer as thickness, element distribution, structure and constituent phases of the alloying layer. In this paper, composition of the alloying layer and its constituent phases were studied for different substrates after the plasma surface alloying with W, Mo and Co. The results showed that the thickness, distribution of elements, structure and constituent phases of alloying layer were influenced greatly by the carbon content of the substrate. It is found the increase in the carbon content in the sample substrate decreases the depth of the surface compound layer. The constituent phases of the surface layer were (FeCo)₇ (WMo)₆-type μ phase, (FeCo)₂ (WMo)-type laves phase and W (Mo) solid solution for the ingot and 20 steel and MC-type carbide and M₆C-type carbide for the 45 steel and the T8 steels, respectively. The surface alloying layer exhibited high hardness of 1200-1400 HV_0.2.The thickness of the surface alloying layer was 120 μm for ingot, 50-95 μm for 20, 45, T8 steels. The advantage of the DGPSA is that thick alloying layer is formed without adhesion problem, almost every metal including W, Mo can be surface-alloyed without environment contamination problem.