Ti(C,N)基金属陶瓷的力学性能与显微结构的研究

烧压烧结制备了不同Mo2C和Cr3C2含量的Ti(C0.7N0.3)-(Ni—Co)-Mo2C—Cr3C2金属陶瓷，对其性能测试表明，低Mo2C，Cr3C2含量材料具有良好力学性能。利用透射电镜、能谱分析和扫描电镜对低Mo2C，Cr3C2含量金属陶瓷显微组织进行了分析。研究表明，材料显微组织中没有发现明显可见的环形相，Mo元素富集在硬质相颗粒边缘附近，Cr元素富集在粘结相中。未完全溶解的Cr3C2分布在粘结相内和相界上抑制了裂纹的扩展，断口上沿晶断裂面弯曲不规整以及穿晶解理条纹较多，这是材料具有较高的断裂韧性的原因。     

Ti(C,N)基金属陶瓷氮化处理后的表面组织结构及形成机理

对Ti(C，N)基金属陶瓷进行了表面氮化处理。用SEM，EPMA，TEM／EDX分析了材料表面显微组织的特征。研究发现，材料表面形成了富N、富Ti的相，它们包覆在硬质颗粒的表面。硬质颗粒周围的环形相的体积分数大大减少。晶粒尺寸也明显减小。紧邻表面硬化层，出现了一层金属粘接相含量较高的过渡层。表面氮化处理使Ti(C，N)基金属陶瓷的表面硬度得到明显的提高，而基本上不影响其抗弯强度。表面较高的-N的活度是促使各合金元素扩散，形成上述特征组织的驱动力。     

(Ti,Mo,W,Ta,V,Nb)(C,N)多元陶瓷相的价电子结构

运用固体与分子经验电子理论(EET理论)计算了(Ti,Mo,W,Ta,V,Nb)(C,N)多元陶瓷相的价电子结构.结果表明,价电子结构参数(nA)随碳化物添加量的增加而增加.不同碳化物对价电子结构参数的影响不同,其中VC的影响最为显著.价电子结构参数(nA)可以用来评价金属陶瓷的力学性能,提出了相关的判据关系式.     

不同含量Ce对Ti(C,N)基金属陶瓷的结构和性能的影响

采用固溶型Ti(C,N)、Mo2C、WC、Co、Ni、Ce作为原料粉末,通过粉末冶金真空液相烧结Ce改性的Ti(C,N)基金属陶瓷材料,并对金属陶瓷复合材料的微观形貌和性能进行分析。研究结果表明,添加稀土Ce后,Ti(C,N)基金属陶瓷的硬质相变得细小且均匀,微观组织中的空隙和缺陷也减少了;随着Ce含量的增加,金属陶瓷材料的维氏硬度、抗弯强度以及断裂韧性均呈现出先增大后逐渐减小的趋势,当Ce的含量增加到0.5 wt%时,金属陶瓷材料的维氏硬度、抗弯强度以及断裂韧性达到最佳,分别为102.3 HRA、902.2 MPa、11.5 MPa·m1/2。     

添加碳化钛对超细Ti(C,N)-Ni金属陶瓷显微结构和力学性能的影响

用传统粉末冶金法制备了添加碳化钛(TiC)的Ti(C,N)基金属陶瓷.为了得到超细晶粒的显微结构,主要硬质相[Ti(C,N),TiC和TiN]的初始粉末粒度为纳米、亚微米级.通过扫描电子显微镜观察,发现了一种新的白芯/灰壳结构,揭示了其形成机制.此外,通过能谱仪分析,获得了各相的化学成分.用X射线衍射仪并通过计算得出了各相的点阵参数.对室温下该材料的力学性能进行了测试,并尝试把它们与金属陶瓷的原始成分和显微结构的特点联系起来.     

碳化钛粒径对碳氮化钛基金属陶瓷微观结构和力学性能的影响

用粉末冶金真空烧结法制备了超细晶粒碳氮化钛[Ti(C,N)]基金属陶瓷.研究了原始粉末粒径对Ti(C,N)基金属陶瓷微观结构和力学性能的影响.结果表明:在化学成分相同的条件下,晶粒细化使材料的Vickers硬度和抗弯强度上升,但断裂韧性有所下降.在超细晶粒Ti(C,N)基金属陶瓷微观组织中出现了一种新型的白芯/灰壳结构和一种特殊化合物(Ni2Mo2.5W1.3)Cx.初步研究表明:由于原始粉末粒径微小,促进了扩散反应因而生成了这种芯/壳结构.芯/壳结构有利于提高材料的抗弯强度和断裂韧性.(Ni2Mo2.5W1.3)Cx有利于提高材料的Vickers硬度,但是降低了Ti(C,N)基金属陶瓷的抗弯强度和断裂韧性.     

Ti(C,N)基金属陶瓷性能影响因素及发展趋势

Ti(C,N)基金属陶瓷作为一种新型的工具材料,具有密度低、室温硬度和高温硬度都优于WC基硬质合金、化学稳定性和抗氧化性好、耐磨性好等优点。介绍了Ti(C,N)基金属陶瓷的基本组成和结构,组织性能及其影响因素,综述了Ti(C,N)基金属陶瓷的研究现状,指出了其未来的发展方向和应用。     

WC含量对Ti(C,N)基金属陶瓷组织和性能的影响研究

用传统的粉末冶金方法制备了不同WC含量的超细Ti(C,N)基金属陶瓷试样,运用SEM,EDX等手段对材料的显微组织进行了表征分析,并用这些显微组织的特征和差异解释了材料宏观力学性能的特点.结果表明,金属陶瓷的组织为典型的两相结构特征,其中陶瓷相的芯、壳结构(core/timstructure)与溶解析出机制有关.少量WC的加入能提高材料的力学性能.断口SEM分析表明:断裂机理为典型的混合型断裂(穿晶断裂和沿晶断裂),金属相存在着明显撕裂的痕迹.     

Mo对Ti(C,N)金属陶瓷组织结构和力学性能影响

以原始粉体作为原料,采用传统的粉末冶金方法制备Ti(C,N)基金属陶瓷,研究不同钼含量对Ti(C,N)金属陶瓷的显微组织结构和力学性能的影响。根据设计的成分配方,采用传统的粉末冶金方法按照优选的工艺来制备一系列的金属陶瓷试样,在不改变金属陶瓷硬度和抗热震能力的基础上,尽量提高其硬度和其他力学性能。对烧结试样的表面进行必要的处理,采用X射线衍射(XRD)、金相显微镜、维氏硬度仪等表征方法研究了Mo含量对Ti(C,N)基金属陶瓷组织结构和力学性能的影响。实验结果表明:Mo含量在(5wt%～10wt%)范围内,材料的相对密度随Mo含量的增加而提高,而Mo含量在(5wt%～10wt%)范围内,材料的相对密度随Mo含量的增加而降低,Mo含量为10wt%时,金属陶瓷的相对密度最高。在Mo含量一定的范围内(5wt%～15wt%),随着Mo含量的增加,硬度先升高后降低,断裂韧性降低,分别掺加10wt%Mo和5wt%Mo时获得最大的硬度和断裂韧性。随着热震温度的升高和热循环次数的增加,金属陶瓷中的裂纹增多;钼含量较低的Ti(C,N)金属陶瓷抗热震性能较好,当钼含量为15wt%时,压痕裂纹扩展较明显。     

添加碳化钛对超细Ti(C,N)–Ni金属陶瓷显微结构和力学性能的影响(英文)

用传统粉末冶金法制备了添加碳化钛(TiC)的Ti(C,N)基金属陶瓷。为了得到超细晶粒的显微结构,主要硬质相[Ti(C,N),TiC和TiN]的初始粉末粒度为纳米、亚微米级。通过扫描电子显微镜观察,发现了一种新的白芯/灰壳结构,揭示了其形成机制。此外,通过能谱仪分析,获得了各相的化学成分。用X射线衍射仪并通过计算得出了各相的点阵参数。对室温下该材料的力学性能进行了测试,并尝试把它们与金属陶瓷的原始成分和显微结构的特点联系起来。     

Effect of Cr3C2 on Valence-Electron Structure and Plasticity of Rim Phase in Ti(C,N)-Based Cermets

Based on the empirical electron theory of solids and molecules, the valence-electron structure (VES) of the rim phase in Ti(C,N)-based cermets was calculated, and the relationship between the VES and plasticity was determined. The results indicated that the plasticity of the rim phase in a Ti(C,N)-based cermet could be defined using the sum of the n _a values for the covalent bonds, and that chromium dissolution in the rim phase improved the plasticity of the rim phase. Moreover, a series of experiments showed that adding Cr₂C₃ to a typical Ti(C,N)-based cermet strengthened the interface. Based on those results, a Ti(C,N)-based cermet with added Cr₃C₂ was manufactured; the new cermet had more than twice the transverse rupture strength of a typical cermet.     

Evolution of microstructure and interfacial characteristics of complete solid-solution Ti(C,N)-based cermets fabricated by mechanical activation and subsequent in situ carbothermal reduction

Complete solid-solution Ti(C,N)-based cermet, with no typical core-rim structure, was synthesized through mechanical activation and subsequent in situ carbothermal reduction method. XRD, SEM, TEM, and C/N analysis were used to investigate the microstructure, phase transformation, and the interfacial characteristics of the present cermets. During solid-state sintering, the (Ti,Mo)C/(Ti,Mo)(C,N) phases formed through the transformation of Mo-based solid solution which generated by mechanical activation. Then, the formed (Ti,Mo)C/(Ti,Mo)(C,N) continuously dissolved into the nickel-based binder above 1100 °C. It was found that in the subsequent stage of liquid sintering, the mechanical activation and also the presence of extremely fine TiC/Ti(C,N) particles accelerated the Mo diffusion into the hard phase, resulting in a large quantity of (Ti,Mo)(C,N) solid solutions formed in the nickel-based binder. Finally, complete (Ti,Mo)(C,N) solid-solution phase was obtained via dissolution and re-precipitation. The higher toughness and transverse rupture strength (TRS) of the synthesized new cermet, as compared with traditional cermets, were mainly caused by the increased crack deflection and transgranular fracture of the novel cermets. Moreover, the interface among the Ni-based binder phase and complete solid solution hard phase exhibited a semi-coherency state with high-density dislocations, which also significantly improved the TRS and toughness of the synthesized cermets.     

Ti(C,N)-based cermets containing uniformly dispersed ultrafine rimless grains: Effect of VC additions on the microstructure and mechanical properties

Difference in lattice parameters and physical properties of core-rim structure leads to mismatch at the core-rim interfaces. In this respect, VC was adopted to shrink the lattice of rims and intended to reduce the lattice misfit. Small amount of VC (0.8 wt%) effectively decreased the grain size from 0.77 μm to 0.57 μm, with an increased lattice parameter of the core-rim phase. Higher VC content accelerated the dissolution and precipitation process, resulting in the formation of thicker rims and smaller lattice parameters of core-rim structure. The same lattice parameters of core-rim phases were achieved with 4.8 wt% of VC addition. A distortion zone with a thickness of 3–5 atomic layers was confirmed, which located at the boundary of binder and gray rim. VC induced the formation of spherical rimless grains, which were uniformly dispersed in the binder and usually attached to the coarse core-rim grains. Black ultrafine rimless grains exhibited larger lattice parameters than Ti(C,N) cores due to the increased C/N ratios. Ti(C,N)-based cermets with uniformly dispersed rimless grains were achieved, which showed effectively improved the bending strength of cermets, with in-situ formed dimples inside the binders during the fracture.     

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

Three series of Ti(C, N)-based cermets with various carbon content were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). Hardness (HV) and transverse rupture strength (TRS) were also measured. A lower carbon content resulted in the aggregation of ceramic grains because the absorbed oxygen of the powder mixture could not be outgassed completely, and then the ceramic grains could not be well-wetted by liquid metal during sintering. On the contrary, too high carbon content resulted in the formation of graphite phase. An increased carbon content decreased the dissolution of tungsten, titanium and molybdenum in the binder phase. The volume fraction of the binder is not much influenced by the carbon content. The highest hardness and TRS were found for the cermet with 1.5 wt.% carbon addition, which was characterized by fine grains and moderate thickness of rim phase.     

Ti(C,N)基金属陶瓷氧化后的显微结构与力学性能

研究了Ti(C,N)基金属陶瓷的高温抗氧化性能。采用X R D、SEM分析了样品氧化后的物相组成及显微结构,并测试了试样氧化前后的抗弯强度和维氏硬度。实验结果表明:Ti(C,N)基金属陶瓷在800℃时氧化不明显,但抗弯强度开始下降;样品在900℃时开始剧烈氧化,材料的抗弯强度呈现明显的下降趋势,试样氧化前后的硬度变化较小。随着氧化温度的升高,氧化层厚度明显增加,Ti(C,N)被氧化变成TiO 2。