粘结剂成分对Ti(C,N)基金属陶瓷腐蚀行为的影响

研究了含38 wt% Ni或Ni–20Cr粘结剂的2种Ti(C,N)基金属陶瓷在0.2 M H2SO4和0.2 M NaOH溶液中的室温腐蚀行为。在0.2 MH2SO4溶液中,2种金属陶瓷的腐蚀行为和耐蚀性存在一些明显的差异：与以Ni作粘结剂的金属陶瓷不同,以Ni–20Cr作粘结剂的金属陶瓷浸泡过程中表面自发生成NiO、Ni(OH)x(SO4)y、Cr2O3和Cr(OH)3,致使粘结相溶解十分缓慢;动电位极化过程中不发生钝化,伪钝化后电流密度增加较快。在0.2 M NaOH溶液中,2种金属陶瓷的腐蚀行为和耐蚀性无明显差异：浸泡过程中陶瓷晶粒溶解十分缓慢,同时生成NiOOH和Cr6+化合物;动电位极化过程中不发生钝化,但发生伪钝化。     

VC/Cr3C2对Ti(C,N)基金属陶瓷微观组织和力学性能的影响

研究VC/Cr3C2对Ti(C,N)基金属陶瓷微观组织和力学性能的影响.利用光学显微镜、X射线衍射仪和扫描电镜结合能谱仪研究微观组织.测试横向断裂强度、硬度和断裂韧性等力学性能.结果表明:微观组织中存在“黑芯-灰壳”和“白芯-灰壳”结构;由于添加VC/Cr3C2,硬质相晶粒变细,添加0.75VC/0.25Cr3C2的金属陶瓷晶粒细化最明显;黑芯随着VC添加量的增加而变细,壳随着Cr3C2添加量的减少而变厚;孔隙率随着VC/Cr3C2中VC的量增加而增大;横向断裂强度和硬度均升高,并且均在添加0.25VC/0.75Cr3C2时达到最大值;按适当的VC和Cr3C2添加量比例添加VC/Cr3C2可以有效地使断裂韧性升高,并在添加0.5VC/0.5Cr3C2时取得最大值.     

CeO2添加量对Ti(C,N)基金属陶瓷显微结构和力学性能的影响

采用真空烧结工艺制备了(56-x)Ti(C0.5,N0.5)-20WC-3.5Mo2C-20(Co+ Ni)-xCeO2(x=0,0.05％,0.1％,0.2％)系列金属陶瓷,研究了CeO2添加量对Ti(C,N)基金属陶瓷显微结构和力学性能的影响.结果 表明:添加适量的CeO2有利于Ti(C,N)金属陶瓷显微组织细化,...     

Mo element-induced wear behavior evolution of self-lubricant Ti(C,N)-based cermets

In the work, Mo element is used to adjust composition and distribution of the lubricating phase of the self-lubricant Ti(C, N)-based cermets. Ring-block wear test of self-mate pairs is conducted. The microstructure and wear behavior evolution of the cermets are investigated. The results indicate by adjusting the content of Mo, the distribution of graphite on the surface of the self-lubricant cermets changes. With the increase of Mo content, the volume of graphite decrease, and the undissolved Mo increase. During self-mate pair sliding wear, the tribolayer transform from graphite to graphite+MoOx and then to MoOx. The cermets with 4 wt%. Mo show the best tribological properties, which shows a smooth and dense composite tribolayer formed mainly by graphite and MoOx.     

Erosion-corrosion behavior of Ti(C,N)-based cermets containing different secondary carbides

The present work investigated the effects of secondary carbides (Mo₂C\WC\TaC\NbC) on the erosion-corrosion behavior of Ti(C,N)-based cermets. The results indicate that the erosion-corrosion resistance of Ti(C,N)-based cermets is enhanced in the order of NbC, TaC, WC and Mo2C addition. The contribution of erosion to the erosion-corrosion of Ti(C,N)-based cermets is much more significant than that of corrosion, and it increases with the decreased mechanical properties. The synergistic effect plays a dominant role in the degradation of Ti(C,N)-based cermets in erosion-corrosion conditions. There are two modes to ceramic phase degradation in erosion conditions: large ceramic grains are prone to deterioration through crack initiation and propagation → grain fracture → fragment removal; finer ceramic grains trend to be pulled out after the deterioration of binder and interface. The binder loss is determined by the corrosion resistance of binder, the erosion resistance of binder and the erosion resistance of ceramic phase.     

碳纳米管添加量对Ti(C,N)基金属陶瓷组织和力学性能的影响

采用真空烧结工艺制备了Ti(C, N)基金属陶瓷,通过XRD、TEM和SEM等手段研究碳纳米管(CNTs)对金属陶瓷组织和性能的影响.结果表明:与未加碳纳米管的基体组织相比,添加CNTs的金属陶瓷组织中具有"白芯-灰壳"结构的小颗粒大大增加,金属陶瓷晶粒逐渐细化且分布均匀;当CNTs添加量(质量分数)为0.5%时,Ti(C, N)基金属陶瓷的硬度可达90.9HRA;金属陶瓷的抗弯强度比未加碳纳米管的试样提高14.1%,可达2 180.7 MPa,其强化机制主要为细晶强化;金属陶瓷的断裂韧性比未加碳纳米管的试样提高18.5%,可达14.7 MPa·m1/2,CNTs对金属陶瓷强韧化机制主要为桥联作用、拔出效应和裂纹偏转作用.     

Effect of VC addition on the microstructure and properties of Ti（C,N）-based nano cermets

In this paper, Ti(C,N)-based nano cermets were prepared by nano particles, and the effect of VC addition on the microstructure and properties of Ti(C,N)-based nano cermets was investigated. The results showed that there existed black-core grayish-rim structure as well as gray-core grayish-rim structure in VC-doped Ti(C,N)-based nano cermets. With the increase of VC addition, the number of gray cores increased, the lattice parameter of Ti(C,N) phase increased, the grain size decreased, the hardness and fracture toughness of Ti(C,N)-based nano cermets were enhanced, and nearly full densification could be achieved. However, excessive addition of VC to 1 wt% resulted in slight decrease in hardness and fracture toughness. Some deep dimples were found in the fracture surface of cermets with VC addition, which corresponded to ductile fracture.     

Ti (C,N)-based cermets sintered under high pressure

In this study, high pressure and high temperature sintering (HPHT) is adopted in the cermet fabrication process, and the microstructure and mechanical properties of cermets with TiC_0.5N_0.5–15WC–10Mo₂C–5TaC–10Ni–10Co (wt%) sintered under 5 GPa and different temperatures (900–1600 °C) using 6 × 14 MN cubic press are investigated. Results show that the densities of samples can reach up to 7.00 g/cm³. Vickers hardness and fracture toughness of the products are over 1727 HV30 and 7.2 MPa m^1/2 respectively. In addition, the sintering results are compared with the data that obtained from commercial samples which produced via conventional sintering technique. The conclusion is that high density and high hardness cermets can be obtained through HPHT sintering.     

Preparation of self-lubricating Ti(C,N)-based cermets by solid carburization and wear behavior

In this work, self-lubricating Ti(C,N)-based cermets were prepared by solid carburization. The sintered cermets were wrapped by carburizing agent and sintered again at 1440 °C with different time. The microstructure and composition of cermets were studied. The wear behavior of cermets containing graphite phase was also evaluated using a block-on-ring tribometer. The results showed that the carbon content increased gradually in binder phase with carburizing time. When the carburizing time was 3 h, the carbon got saturated in binder phase. When the carbon content exceeded the solubility in the binder, excessive carbon precipitated and formed graphite phase. Uniformly distributed graphite clusters formed in cermets after carburization for 4 h. The graphite clusters consisted of flocked graphite particles. With the carburizing time extended to 5 h, the graphite clusters became large and some of them interlaced together. Besides, the wear results indicated that the volume loss of cermets containing graphite phase was half of that without graphite due to the formation of smooth tribofilm on the worn surface of cermets.     

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.     

Corrosion behavior of Ti(C,N)-Ni/Cr cermets in H2SO4 solution

The effects of partial substitution of Ni with Cr on the microstructure and corrosion resistance of Ti(C,N)-based cermets in H₂SO₄ solution were investigated in this paper. The results showed that partial substitution of Ni with Cr had a minor effect on the microstructure, whereas the hardness of the Ti(C,N)-based cermets could be improved for dissolution of Cr in Ni binder. The corrosion behavior of Ti(C,N)-based cermets with different Cr content in 0.2 mol/L H₂SO₄ solution was also studied via potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and corrosion test. The tested Ti(C,N)-Ni/Cr cermets had three typical passive regions. The current of the first passive region was reduced and the passive range was enlarged with the increase of Cr content in binder attributed to the synergistic effect of Ti-based and Cr-based passive layers. But the remaining passive regions were pseudopassive regions. The EIS results also demonstrated that the impendence of the reaction rose with the increase of Cr content in binder. Moreover, the corrosion resistance of cermets in H₂SO₄ solution was improved remarkably by Cr dissolving in the binder, which gave rise to the enhanced passivation ability.     

Ti(C,N)基金属陶瓷/40Cr钢钎焊接头减应措施

选用Cu,Nb,Mo箔中间层,在特定的焊接参数条件下对Ti(C,N)基金属陶瓷/40Cr钢接头进行了钎焊试验,分析比较了中间层与钎料的不同匹配对抑制裂纹形核及扩展的影响.结果表明,中间层Cu能有效释放接头残余应力,防止接头产生裂纹;中间层Nb易溶解并聚集成带状,并在该带状组织与钎缝界面萌生裂纹;中间层Mo的减应效果较差.影响Ti(C,N)基金属陶瓷/40Cr钢钎焊接头残余应力的因素很多,应综合考虑各因素才能达到有效降低接头应力的目的.     

纳米改性Ti(C,N)基金属陶瓷的抗热震性能研究

为研究不同金属相对纳米TiN改性Ti(C,N)基金属陶瓷抗热震性能的影响,采用真空烧结法分别制备了Ti(C,N)基20Ni、10Co-10Ni和20Co三组金属陶瓷,用急冷-强度法测定了其抗热震性能.结果表明,3组金属陶瓷试样的热震残留强度均随热震温度的升高而降低,其热震残留强度急剧下降的临界温度分别为410、370和330℃.扫描电镜分析结果表明,热震后试样的组织仍然保持着金属陶瓷典型的芯/壳结构,随着热震温度的升高,组织中出现裂纹,断口中有气孔及裂纹出现,导致材料强度下降.对热震试样硬度的测试结果表明,纳米TiN改性Ti(C,N)基金属陶瓷在热震后仍然具有很高的硬度.     

纳米TiN改性Ti（C, N）基金属陶瓷的组织和性能

采用真空烧结法制备纳米TiN改性的Ti（C, N）基金属陶瓷,研究不同金属相对纳米改性Ti（C, N）基金属陶瓷组织和力学性能的影响。结果表明：除经典的黑芯/灰壳组织外,添加纳米TiN的金属陶瓷在黑芯内还出现灰芯结构;纳米TiN主要分布在陶瓷相颗粒的晶界处;相对于未添加纳米TiN的金属陶瓷,添加纳米TiN粉末能明显提高金属陶瓷的抗弯强度、硬度与断裂韧性;对纳米TiN改性的金属陶瓷而言,金属相Ni能提供更好的抗弯强度与断裂韧性,而金属相Co则能带来更高的硬度。     

Effect of graphite size on the tribological behavior of Ti (C,N)-based cermets self-mated wear pairs

In the present work, graphite of different particle size ranging from 2 μm to 32 μm is added into the system to lubricate the Ti (C, N) cermets, but the addition amount is fixed at 1 wt%. The sliding wear tests were carried out using block-on-ring equipment. The distribution morphology of graphite, mechanical properties and wear behavior were studied in this paper. The results indicate that when the graphite is added into the cermet, graphite particles join together and are distributed to clusters of different size which are like bird nests. The range of the “bird-nest” clusters increase with the improvement of graphite size when the graphite particle size is smaller than 12 μm but decrease when larger than 12 μm. Furthermore when the graphite grain size increase to 32 μm, most of the particles exist in the cermets individually instead of distributing like bird nest The mechanical properties decrease with the improvement of graphite size, and when the particles size of graphite increase to 32 μm the mechanical properties get worse sharply. The wear mechanism of the cermets with graphite, adhesion and plastic deformation are dominated. The extruded graphite forms a tribofilm, and protects the surface from the hard abrasive particles ploughing. When the particles size of graphite added is 22 μm, cermets which have coarser graphite particles and more but moderate-in-size graphite clusters possess the best effect of lubrication     

Effects of NiTi additions on the microstructure and mechanical properties of Ti(C,N)-based cermets

X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to observe and investigate the microstructure and fracture morphology of Ti(C,N)-based cermets added with NiTi alloy powder. A new ceramic phase is found with the structure of gray core, black inner rim, noncontinuous white inner rim and continuous gray outer rim. The fracture toughness and the transverse rupture strength have a distinct trend to increase with the increase of NiTi powder content in Ti(C,N)-based cermets, while the hardness has the opposite trend. Grain refinement and the increase of metallic phase are the dominant strengthening and toughening mechanisms. Additionally, the crack deflection and bridging may play an active role in improving the properties, as well as the special structure of large metallic binder containing many small ceramic particles. In cermets with a higher content of NiTi powder, the microcrack and the crack closure effect induced by martensitic transformation are advantageous to the mechanical properties.     

Cr_3C_2对纳米Ti（C,N）基金属陶瓷组织和性能的影响

研究了Cr3C2含量对纳米Ti（C,N）基金属陶瓷组织和性能的影响。测定了抗弯强度、硬度和断裂韧度;进行了XRD相结构分析;用扫描电镜观察了组织结构与断口形貌。结果表明,Cr3C2添加量为1.5%时,材料的综合性能最好。     

Ti(C,N)基金属陶瓷断口形貌及增韧机理

采用真空烧结工艺制备Ti(C,N)基金属陶瓷,测定了材料的力学性能。结果表明,其力学性能与未加纳米粉的金属陶瓷相比,硬度略有升高,但横向断裂韧性提高了近一倍。断口形貌和微观组织分析表明:金属陶瓷的断口形貌与其强韧性有着密切的关系。纳米粉的加入降低了原始粉末的平均粒度,使得金属陶瓷硬质相的粒度降低,减小了晶粒间的平均自由程。镶嵌于大颗粒环形相和弥散分布于粘结相中的细小硬质相颗粒,对裂纹的形成和扩展起到阻碍作用,会使金属陶瓷因裂纹扩展途径发生偏转而增韧。     

Early high-temperature oxidation behavior of Ti(C,N)-based cermets with multi-component AlCoCrFeNi high-entropy alloy binder

The early high-temperature oxidation behavior of Ti(C,N)-based cermets with equiatomic AlCoCrFeNi high-entropy alloy binder has been studied, as well as the cermet with Ni/Co binder as a reference. Experiments were performed at the temperature range of 800–1100 °C in static laboratory air. The micro-structural evolution of the multi-layered oxide scales on the cermets was investigated and the effect of binder phase constituent on the oxidation characteristics of Ti(C,N)-based cermets was evaluated. The results demonstrated that the cermet with AlCoCrFeNi multi-element alloy binder possesses superior oxidation resistance, which is greatly better than that of the cermet with Ni/Co metallic binder under the same condition. We suggest that the formation of a continuous and dense external oxide scale can effectively impede the outward diffusion of volatile tungsten oxides and inward oxygen transport, leading to a remarkable improvement of oxidation resistance. In addition, the enhanced oxidation resistance was related to the high Cr and Al concentration in AlCoCrFeNi binder phase that urges the formation of oxide layers with more efficient passivation effect against oxidation.     

Ultrafine (Ti, M)(C, N)-based cermets with optimal mechanical properties

A tough and strong cermet with the composition (Ti,20M,0.2V)(C,N)-16M-20Ni/Co (M = W,Mo) was prepared by mixing WC and Mo₂C with ultrafine (Ti,M)(C,N) powders, and then, processed via a conventional P/M technique. It has an ultrafine and distinct core/rim structure, resulting in excellent mechanical properties: bending strength of 2210 MPa, HV hardness of 14.7 GPa and toughness of 10.1 MPa m^1/2. The small concentration gradient in core/rim composition and the disappearance of inner rims benefit the reduction of the stress concentration at the core/rim interface in (Ti,M)(C,N)-M_xC cermets, and thus improve their toughness. In addition, ultrafine microstrucure improves mainly their bending strength and hardness.