Ti(C,N)基金属陶瓷制备工艺研究

实验采用日本新金属公司的TiC0.7N0.3,TiC0.5N0.5两种原料粉末,比较在不同制备工艺条件下,Ti(C,N)基金属陶瓷材料的力学性能。结果表明,原料、湿磨工艺、烧结工艺、烧结后的低压热等静压显著影响合金的力学性能及金相组织。     

NiTi短纤维对Ti(C,N)基金属陶瓷组织和性能的影响

本文研究了添加直径为0.08mm、长度为2mm、添加量0～16wt%、等原子比的NiTi合金短纤维对Ti(C,N)基金属陶瓷组织和性能的影响,试样采用粉末冶金的方法制备,采用OM、XRD、SEM等对其进行分析。结果表明,压制成型时,随着NiTi短纤维加入量的增加,原料的流动性逐渐变差,导致压成的素坯的致密度降低;在烧结过程中,由于大部分Ni形成Ni-Co固溶体或被蒸发,因此大部分NiTi合金的原子比被破坏,烧结时液态的NiTi会填充试样内部的空隙,由于素坯的致密度较低,液相不能完全填充,导致在冷却后金属陶瓷中出现了许多孔洞,且随着NiTi合金短纤维加入量的增加,金属陶瓷的孔洞逐渐增加,其致密度和抗弯强度也随着下降。     

镍钴对超细Ti(C,N)基金属陶瓷性能的影响

研究了Co部分和全部代替Ni对超细Ti(C,N)基金属陶瓷性能的影响。采用X射线衍射仪对物相研究发现:金属相中w(Co)=10%和w(Co)=15%时,金属陶瓷中出现金属间化合物,并且有两种Co的同素异构体并存;力学性能测试表明:5%的Co取代5%的Ni可以明显提高金属陶瓷的抗弯强度、硬度和断裂韧性。金属相为10%Ni-5%Co时,材料的综合力学性能最好。     

二次低压烧结对Ti(C,N)基金属陶瓷组织与性能的影响

本文对真空烧结后的Ti(C,N)基金属陶瓷进行了二次低压烧结并对材料的组织和性能做了研究。研究发现,二次低压烧结后,Ti(C,N)基金属陶瓷中出现了一些白色的芯相组织,与黑色的芯相比,其Mo含量更高,而Ti含量更低。低压烧结后,金属陶瓷中的孔隙减少了,硬质相平均晶粒度从0.8μm增加到0.9μm。金属陶瓷的线收缩率从18.7%增加到20.3%;相对密度从99.19%增加到99.31%;硬度从93 HRA下降到92.8HRA;横向断裂强度从1 587 MPa增加到1 844 MPa。从断口形貌看,二次低压烧结后金属陶瓷断口中硬质相内部的微裂纹减少了,而且穿晶断裂的现象增多。     

Ti(C,N)基金属陶瓷材料显微结构与性能研究进展

对国内外近年来有关Ti(C,N)基金属陶瓷材料的显微结构与性能的研究成果进行了总结。首先,介绍了Ti(C,N)基金属陶瓷材料的发展史;Ti(C,N)基金属陶瓷的显微结构、力学性能,以及显微结构与其性能的关系等。其次,列举并比较了不同的烧结方法所制备的Ti(C,N)基金属陶瓷材料的力学性能;结果表明:微波烧结和放电等离子烧结技术在较低的温度就可以成功烧结高硬度、高抗弯强度与断裂韧性高的产品,但实际生产中,这类技术还没有广泛被应用,应用最广的是真空烧结方法。最后介绍了Ti(C,N)基金属陶瓷材料的今后的研究趋势。     

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。     

烧结工艺和粘结相对Ti(C,N)基金属陶瓷微观组织的影响

采用真空烧结法制备了高密度Ti(C,N)基金属陶瓷,通过SEM和EDS等分析手段分别研究了烧结工艺参数和粘结相成分对Ti(C,N)基金属陶瓷显微组织和断口形貌的影响.结果表明:经1220℃保温2h处理后的试样显微组织致密,气孔少,具有典型的“芯-环”结构且分布均匀,其断口形貌呈现出较多的韧窝和发达的撕裂棱,断口整体较为致密、层次感较强;在相同的烧结工艺下,粘结相成分为10％Ni5％Co的Ti(C,N)基金属陶瓷组织致密、晶粒细小,粘结相分散更加均匀,断裂方式主要是沿晶断裂,伴有大量断裂韧窝和发达的撕裂棱的出现.高含量Co替代Ni的Ti(C,N)基金属陶瓷试样断口形貌较为平整、发亮,具有穿晶断裂特征.     

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。     

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。     

细晶粒Ti(C,N)基金属陶瓷制备技术与性能

对近年来国内外有关细晶粒Ti(C,N)基金属陶瓷制备技术的研究成果进行了分析总结。简要介绍了混料技术、烧结技术对材料晶粒度及组织、性能的影响,概述了新的工艺方法抑制晶粒长大的机理,指出了细晶粒Ti(C,N)基金属陶瓷制备技术的发展方向。     

Effect of sintering on microstructures and properties of sub-micron Ti （C, N）-based cermets

The influence of different sintering processes, including vacuum sintering, vacuum sintering followed by HIP and sintering-HIP, on the microstructure and properties of sub-micron Ti(C,N) cermets with various binder contents was studied. Image analysis based on back-scattered electrons image observations was used to determine the morphologic and structural characteristics. Transverse rupture strength(TRS), hardness, fracture toughness were measured and TRS data were treated by Weibull statistics further. It is shown that a very significant improvement in TRS can be obtained by HIP or sintering-HIP treatment for the alloys with lower and middle binder content at the controlled cooling rate, but the effect is not obvious for the alloys with higher binder content. HIP is also helpful for improving the hardness of sub-micron Ti(C,N) cermets, however, but can lower the fracture toughness. The varia-tion of these properties was interpreted in terms of the difference in morphologic and structural characteristics.     

烧结气氛对Ti(CN)基金属陶瓷组织和性能的影响

用X射线衍射、背散射扫描电镜及能谱仪等分析手段研究了烧结气氛(真空、N2、Ar)对不同成分TiC基和Ti(CN)基金属陶瓷合金显微组织和性能的影响.金属陶瓷在N2和Ar中烧结后,合金碳含量比在真空中烧结的碳含量低0.5%左右;在N2中烧结后,合金的氮含量提高了0.5%左右.环状结构心部可以是以钨等重金属元素为主要成分的碳化物,也可以是以钛为主要成分的碳化物和碳氮化物.环状结构为金属元素含量和分布不同的(Ti,W,Ta,Mo,Co,Ni)(C,N)固溶体,粘结相是与Ti,W,Ta,Mo,C,N等元素有不同溶解度的钴镍固溶体.真空烧结后组织结构比较均匀,合金的性能最好.在Ar、N2中烧结后,气氛中的氧和氮参加烧结反应,影响合金成分碳氮平衡,在合金表面形成壳层结构,产生表面缺陷,合金的密度、显微硬度、抗弯强度均有比较大的降低;N2气氛影响更大.     

Effect of submicron Ti(C,N) on the microstructure and the mechanical properties of Ti(C,N)-based cermets

There is an increased industry demand for Ti(C,N)-based cermets with improved material properties. One of the parameters which are supposed to influence these properties is the mean particle size of the Ti(C,N) powder used. In this study the effects of a newly developed submicron Ti(C,N) powder grade on the properties of Ti(C,N)-based cermets, including hardness, toughness and microstructure were investigated. The cermets showed only small differences with respect to outgassing upon sintering (investigated by MS-EGA) as well as shrinkage (dilatometry). Cermet formulations with submicron Ti(C,N) could be sintered under identical conditions as with fine Ti(C,N), yielding completely dense bodies of A00 porosity. From SEM and XRD investigations it was found that submicron Ti(C,N) powders cause accelerated diffusion and homogenisation of the microstructure leading to a substantially increased amount of outer rim phase, a higher amount of inverse grains and substantially finer and less Ti(C,N) cores. Upon using submicron Ti(C,N), hardness (HV10) is increased and in one grade the fracture toughness (Palmqvist–Shetty) is increased as well.     

Influence of preparation process on sintering behavior and mechanical properties of ultrafine grained Ti（C, N）-based cermets

The influences of forming and sintering processes on distortion, cracking as well as mechanical properties of sintered bodies of ultrafine grained Ti（C, N）-based cermets were investigated. The results show that lubricant is indispensable to fabrication of ultrafine Ti（C, N）-based cermets, however, with low binder content in powder mixture, the lubrication action of paraffin is attenuated. A appropriate level of 2% （mass fraction） paraffin is determined for a cermet with binder content of 36% （mass fraction）. It is also found that the influence of compaction pressure on distortion and cracking of sintered bodies presents a complex relationship. A relatively lower or higher compaction pressure, less than 100 MPa and more than 400 MPa respectively, favors uniform density distribution in green compact. The heating rate of sintering should be strictly controlled. Too fast heating rate results in enclosed pores to burst and forms large size pores in sintering body. A heating rate of 3 ℃/min is recommended.     

Preparation and properties of ultra-fine TiCN matrix cermets by vacuum microwave sintering

Ultra-fine titanium carbonitride (TiCN) matrix materials with a grain size less than 1 μm were successfully prepared by vacuum microwave sintering. The milling process for raw TiCN particles and the microstructure and properties of cermets produced with a composition of 15wt.%WC-17wt.%(Co+Ni)-9wt.%Mo₂C-59wt.%Ti_0.7N_0.3 and sintered by vacuum microwave were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that a ball-to-powder mass ratio of 8:1 and a milling time of 50 h provided appropriate conditions for the production of ultra-fine TiCN solid solution powders. The use of vacuum microwave sintering produced cermets with much finer grain and black core structures and higher relative density and hardness than those produced by vacuum sintering technology.     

Ti(C,N)粉末制备技术的研究及进展

概括了国内外Ti(C,N)粉末的制备技术,特别系统地介绍了Ti(C,N)粉末的制备技术的最新进展,分析了这些制备技术的工艺过程和工艺特点,讨论了其存在的问题和发展趋势。     

Comparative study of the fabrication of ultrafine Ti（C,N）-based cermets by spark plasma sintering and conventional vacuum sintering

Spark plasma sintering (SPS) and conventional vacuum sintering (VS) were employed to fabricate ultrafine Ti(C,N)-based cermets. The shrinkage behavior, microstructure, and porosity and mechanical properties of the samples fabricated by SPS were compared with those of the samples sintered by VS using optical microscopy, scanning electron microscopy, universal testing machine, and rockwell tester. The results are as follows: (1) The shrinkage process occurred mainly in the range of 1000-1300℃ during the VS process, and only a 0.2% linear shrinkage ratio appeared below 800℃；during the SPS process, a 60% dimensional change occurred below 800℃ as a result of pressure action. (2) By utilizing the SPS technique, it is difficult for obtaining fully dense Ti(C,N)-based cermets. Due to the much existence of pores and uncombined carbon, the mechanical properties of the sintered samples by SPS are inferior to sintered ones by VS. (3) grain size of the samples sintered by SPS is still below 0.5μm, but not by VS; because of low sintering temperature, there are no typical core/rim structures formed in the sintered samples by SPS1; the main microstrures of the sintered samples by SPS2 are a white core/grey shell sstructure, whereas by VS show a typical black core.grey shell structure.     

Effect of VC addition on sinterability and microstructure of ultrafine Ti(C, N)-based cermets in spark plasma sintering

The effect of vanadium carbide (VC) addition on the sinterability and the microstructure of ultrafine Ti(C, N)-based cermets consolidated through spark plasma sintering (SPS) was systematically investigated using optical microscope, scanning electron microscope (SEM) with X-ray energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and transmission electron microscope (TEM). Our results reveal that the addition of VC increases the porosity of sintering body and depresses the sinterability of Ti(C, N)-based cermets. It is also found that the VC addition has a significant influence on the microstructure of ultrafine Ti(C, N)-based cermets, which inhibits the dissolution of titanium-containing compounds and the formation of inner rim phase and outer rim phase, thus preventing from grain growth. Owing to the depressed dissolution and precipitation, nitrogen liberation is mitigated, therefore resulting in less amount of graphite phase in the samples. In substance, VC changes the solubility of metallic elements in the binder, which makes more elements of Mo and W to be reserved in the binder and thus greatly decreases the content of titanium dissolved into the binder. The re-building solubility rule determines the development of phases and microstructure.     

Effect of sintering time on the microstructure and mechanical properties of (Ti,Ta)(C,N)-based cermets

Complete solid-solution cermets based on titanium–tantalum carbonitride using a starting nominal composition with 80 wt.% of (Ti_0.8Ta_0.2)(C_0.5N_0.5) and 20 wt.% of Co were performed by pressure-less sintering at 1550 °C for different times (from 0 to 180 min) in an inert atmosphere. Chemical and phase analyses were conducted using X-ray diffraction (XRD), elemental analysis and energy dispersive X-ray spectrometry (EDX). The binder mean free path and the contiguity of the carbonitride particles were used to rationalise the microstructural effects of the mechanical behaviour. Mechanical characterisation included determining the Vickers hardness, the fracture toughness (conventional indentation microfractures, IM), the dynamic Young's modulus (ultrasonic technique), the biaxial strength (ball on three ball) and a detailed fractographic examination. Finally, the experimental findings were combined with a theoretical fracture mechanics analysis to estimate the critical processing flaw sizes. Binder-less carbonitride clusters, pores and coarse carbonitride grains were the main defects observed and were responsible for the fractures.