Ti(C,N)基金属陶瓷的研究进展

介绍了Ti（C，N）基金属陶瓷的基本组成和结构，综述了Ti（C，N）基金属陶瓷的研究现状，指出了未来的发展方向和应用。     

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。     

Ti(C,N)基金属陶瓷的显微结构和力学性能研究

采用真空热压烧结工艺制备三种不同掺杂的Ti（C,N）基金属陶瓷。借助于SEM分析了其显微结构,并测试了其力学性能和相对密度。实验结果表明：配方41.2wt%TiC-10wt%TiN-14wt%（Ni＋Co）-12wt%Mo2C-15wt%WC-6wt%TaC-0.8wt%Cr2C3-1wt%C的金属陶瓷综合性能最好,晶粒较细、均匀,具有明显的黑芯-灰壳结构;气孔较少,致密度较高。断裂机理主要是沿晶断裂,部分为混合型断裂（穿晶断裂和沿晶断裂）。金属相存在着明显的撕裂棱。其维氏硬度为12.5GPa,断裂韧性为8.9MPa·m1/2,抗弯强度为1286MPa,相对密度达到了99.2%。     

Ti(C,N)基金属陶瓷烧结工艺的现状及进展

介绍了Ti(C,N)基金属陶瓷的性能,主要综述了Ti(C,N)基金属陶瓷在高速刀具的应用和制备工艺的基本原理。着重讨论了各种烧结工艺的优缺点,并展望了Ti(C,N)基金属陶瓷未来的发展方向。     

Ti(C,N)基金属陶瓷显微组织的研究

用粉末冶金方法制备了Ｔｉ（Ｃ,Ｎ）基金属陶瓷,其硬度、抗弯强度和断裂韧性分别可达ＨＲｎ９１．２,１２５０ＭＰａ和１３．４ＭＰａ·ｍ＾１／２同样ＴＥＭ研究表明,陶瓷相／金属相、陶瓷相／陶瓷相界面分别存在一定的取向关系,揭示了液相在烧结后的凝固过程。     

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)基金属陶瓷抗弯强度的价电子判据研究

利用固体分子经验电子理论,计算了金属陶瓷中三元复合陶瓷相（Ｔｉ,Ｍｏ,Ｗ）Ｃ,四元复合陶瓷相（Ｔｉ,Ｍｏ,Ｗ,Ｎｂ）Ｃ和（Ｔｉ,Ｍｏ,Ｗ,Ｔａ）Ｃ五元复合陶瓷相（Ｔｉ,Ｎｏ,Ｗ,Ｎｂ,Ｔａ）Ｃ的价电子结构,探讨陶瓷相的价电子结构与金属陶瓷抗弯强度关系,提出判据关系式,此外,还进行了抗弯强度的实验验证。     

粉末分散对Ti(C,N)基金属陶瓷力学性能的影响

由平均粒径为0．2μm的TiC，TiN细粉，经1430℃，1h真空烧结制备了Ti(C，N)基金属陶瓷。由扫描电镜和强度、硬度测量研究了金属陶瓷的微观结构和性能。原料粉末以聚氧乙烯十二烷基醚为分散剂．蒸馏水为液体介质，溶液pH值保持在6～7之间，并使用超声波分散，悬浮液过筛后烘干。扫描电镜分析表明：经分散后的粉末颗粒团聚较少、分散良好。分散后细粉以相同工艺制备得Ti(C，N)基金属陶瓷。与未分散细粉烧结体对比表明：由分散细粉获得的金属陶瓷的硬度、抗弯强度均优于未分散细粉制备的烧结体，前者的硬度HRh为90．2，抗弯强度为2108MPa；后者分别为89和1983MPa，其微观结构特征为存在较多的细小均匀的黑芯白壳包覆层结构。细粉分散后，颗粒大小的分布较均匀而影响了液相烧结中的溶解-析出过程，这是金属陶瓷微观结构和性能得到改善的重要原因。     

Er对Ti(C,N)基金属陶瓷结构和力学性能的影响

了添加稀土金属Ｅｒ对Ｔｉ（Ｃ,Ｎ）基金属陶瓷结构和力学性能的影响。结果表明,加入稀土ｒ能有效地提高金属陶瓷的硬度,抗弯强度和断裂韧性。     

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.     

Enhancing cutting performance of Ti(C,N)-based cermet tools on nodular cast iron by incorporating high-entropy carbide

In this study, we investigated the cutting performance and wear mechanisms of Ti(C,N)-based cutting tools containing varying weight percentages (0%, 5%, 10%, and 15%) of high-entropy carbide (HEC) (V_0.2Nb_0.2 Mo_0.2Ta_0.2W_0.2)C phase, when used for turning nodular cast iron. According to the turning test results, the cermet cutting tools containing 0 wt%, 5 wt%, 10 wt%, and 15 wt% HEC phases demonstrated effective cutting lives of 402, 720, 632, and 465 s, respectively. The tool with 5 wt% HEC phase showed the best cutting performance. When cutting nodular cast iron with cermet cutting tools, the main wear mechanisms observed were diffusion, oxidation, adhesion, and abrasion on the flank surface, along with diffusion, oxidation, and abrasion on the rake surface. The results of this study indicated that (V_0.2Nb_0.2Mo_0.2Ta_0.2W_0.2)C could be adopted as an effective reinforced phase in the cermet cutting tools.     

Submicron Ti(C,N)-based cermets with improved microstructure using high-energy milled and subsequent heat-treated ultrafine Ti(C,N) powders

Ti(C,N)-based cermets with ultrafine or submicron black core-rim grains are attracting candidates for high-quality tools and dies, due to their high hardness and strength. However, high chemical activity of ultrafine Ti(C,N) powders lead to the increased instability and difficulty to control the sintering process, since the denitrification and interface diffusion are accelerated during the solid-state reaction. Based on this, owing to the unrealized commercial ultrafine-grade powders, ultrafine Ti(C,N) powders with an average grain size around 150 nm, low oxygen content and few dislocations are fabricated via the high-energy ball milling and subsequent heat treatment of commercial micron Ti(C,N) powders. Related morphology evolution, microstructure and composition of the ultrafine Ti(C,N) powders are investigated. Dense submicron Ti(C,N)-based cermets with grain size of 0.62 μm and uniform core-rim phases are successfully prepared by using the as-fabricated ultrafine Ti(C,N) powders. Compared to cermets via the conventional high-energy milling route, submicron Ti(C,N)-based cermets exhibit higher hardness of 1750 ± 40 N/mm², bending strength of 1960 ± 135 MPa, and satisfactory fracture toughness of 9.2 MPa m^1/2, owing to smaller grain size, uniform microstructure and partial black core-rim grains.     

Effect of Carbides on the Microstructure and Properties of Ti(C,N)-Based Ceramics

Ti(C,N)-based ceramics that contained various carbides were prepared via pressureless sintering, to study the effects of the carbides on the microstructure and properties of the ceramics. All the systems showed good densification behavior and formed solid solutions. Impurities introduced from the milling media were sufficient to promote the densification of the ceramics. The grain structures of the systems were a function of carbide crystal structure and their affinity with nitrogen. Microhardness, three-point flexural strength, and fracture toughness of the Ti(C,N)-based ceramics were measured and determined to be 16-18 GPa, 0.7-1.1 GPa, and 3.5-5.5 MPa·m^1/2, respectively.     

Effect of Nano-Size Powders on the Microstructure of Ti(C,N)-xWC-Ni Cermets

Microstructural and compositional analyses of Ti(C,N)– x WC–20Ni cermets were performed to understand the dissolution behavior of nano-size Ti(C,N) and WC, compared with an ultra-fine and a micro-sized system. The WC content was varied from 10 wt% to 70 wt%. The rapid dissolution and reprecipitation of nano-Ti(C,N) powders induced the formation of a coreless microstructure. With an increase in the amount of WC, the concentration of W in the rims increased but was low compared with the ultra-fine or micrometer system. An inversion in W concentration between the inner rim and the outer rim occurred at ∼40 wt% added WC. That is, the outer rim was richer in W than the inner rim. Powder size strongly affected the dissolution and precipitation of particles and was a major determinant of the final microstructure and compositions of the rims. Furthermore, a significant improvement in toughness in the case of simple nano systems was found, compared with that of the corresponding micrometer and ultra-fine systems ( K _{I C} 10–12 vs. 6–10 MPa·m^1/2). The coreless microstructure and the high fraction of rim phase in the nano system are responsible for this difference.     

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。     

Oxidation of Ti(C,N)-Based Ceramics Exposed at 1373 K in Air

Ti(C,N)-based ceramics that contained NbC, TaC, and WC were exposed at 1373 K in air for 10 h to study the effect of these metal carbides on the oxidation resistance. The addition of 10 mol% of NbC and 10 mol% of TaC to Ti(C,N) ceramics improved the oxidation resistance, whereas additions of 10 mol% of WC worsened the oxidation resistance. Weight gain due to the oxidation of Ti(C,N) ceramics with added WC varied in a complicated way, relative to the amount of WC that was involved. There was a competition between weight gain due to the oxidation and weight loss due to the volatile tungsten oxide.