Effect of V content on microstructures and properties of TiC cermet fusion welding interface

The effects of vanadium(V)on the microstructures and mechanical properties of the TiC cermet fusion welding interface were studied by adjusting the content of V in the self-developed flux-cored wires using metal inert gas arc(MIG)welding for surfacing on the TiC cermet.The results show that the increase in V content promotes the element diffusion between TiC cermet and weld metal.There are no de-fects observed in the interface,and the diffusion of elements refers to excellent metallurgical bonding.The shear strength of the fusion zone initially decreases and then increases with the increase in V content.The maximum shear strength of the TiC cermet/weld interface,reaching 552 MPa,occurred when the V content reached 0.65%.Meanwhile,the average hardness in the transition zone reached 488.2 HV0.2.

EFFECT OF BRAZING TIME ON TiC CERMET/IRON JOINT BRAZED WITH Ag-Cu-Zn FILLER METAL

The brazing of TiC cermet to iron was carried out at 1223K for 5-20min using Ag-Cu-Zn filler metal. The formation phase and interface structure of the joints were investigated by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the joint strength was tested by shearing method. The results showed: there occurred three new formation phases, Cu(s.s), FeNi and Ag(s.s) in TiC cermet/iron joint. The interface structure was expressed as TiC cermet/Cu(s.s)+FeNi/Ag(s.s)+a little Cu(s.s)+a little FeNi/Cu(s.s)+FeNi/iron, With brazing time increasing, there appeared highest shear strength of the joints, the value of which was up to 252.2MPa when brazing time was 10min.

Partial transient-liquid-phase bonding of TiC cermet to stainless steel using impulse pressuring with Ti/Cu/Nb interlayer

Partial transient liquid phase （PTLP） bonding of TiC cermet to 06Cr19Ni10 stainless steel was carried out. Impulse pressuring was used to reduce the bonding time, and a Ti/Cu/Nb interlayer was employed to alleviate the detrimental effect of interfacial reaction products on the bonding strength. Successful bonding was achieved at 885℃ under a pulsed pressure of 2-10 MPa within durations in the range of 2-8 min, which was notably shortened in comparison with conventional PTLP bonding. Microstructure characterization revealed the o- phase with a limit solubility of Nb, a sequence of Ti-Cu intermetallic phases and solid solutions of Ni and Cu in α＋β Ti in the reaction zone. The maximum shear strength of 106.7 MPa was obtained when the joint was bonded for 5 rain, indicating that a robust metallurgical bonding was achieved. Upon shear loading, the joints fractured along the Ti-Cu intermetallics interface and spread to the interior of TiC cermet in a brittle cleavage manner.

Numerical Simulation of Brazing TiC Cermet to Iron with TiZrNiCu Filler Metal

The maximum thermal stress and stress concentration zones of iron/TiC cermet joint during cooling were studied inthis paper. The results showed that the shear stress on iron/TiC cermet joint concentrates on the interface tip andthe maximum shear stress appears on the left tip of iron/TiZrNiCu interface. Positive tensile stress on TiC cermetundersurface concentrates on both sides of TiC cermet and its value decreases during cooling. Negative tensile stresson TiC cermet undersurface concentrates on the center of TiC cermet and its value increases during cooling. Brazingtemperature has little effect on the development and maximum thermal stress.

Numerical simulation of TiC cermet/iron joint brazed with Ag-Cu-Zn filler metal

Stress concentration zones and the maximum value of thermal stress of TiC cermet/iron joint brazed with Ag-Cu-Zn filler metal during cooling were studied. The results show that when the temperature is 300K, the maximum values of shear stress and tensile stress on TiC cermet/iron interface both appear on the tip of Ag-Cu-Zn/iron interface, which makes Ag-Cu-Zn/iron interface become weak zone of the interface. Tensile stress on iron undersurface relaxes to the inner of iron, and the compression stress on iron undersurface concentrates on the side of iron as the temperature decreases, so cracks appear easily at the site where tensile and compression stress cross.

Microstructure of TiAl/TiC cermet joint bonded by combustion synthesis

TiAl alloys were joined to TiC cermets using combustion synthesis method. The Ti-C-Ni metallic powder compact acted as a joining interlayer in the joining process. The identification and mechanisms of the reaction at the interface and interlayer were investigated. From the analysis of the microstructure of TiAl/TiC cermet joint, it is noted that TiC and TiNi compounds are main reaction products and unreacted Ni is observed in the interlayer. The reaction products consist of a large volume of voids or unreacted regions. It is confirmed that Al addition as well as joining pressure are effective to decrease the voids. It is considered that high flowability of liquid Al enhances the SHS reaction and the densification of reaction products. There is a continuous Ni-rich layer observed at the interface between the interlayer and TiC cermets substrate. Ti3Al, TiC and TiNi compounds are observed in the reaction products.

Effect of Rare Earths on Microstructure and Properties of TiC-based Cermet/Cu Alloy Composite Wear Resistant Materials

The effect of rare earth (RE) oxide on the microstructure and properties of TiC based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope (TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro-porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardness of the matrix metal can not be effectively increased by adding RE oxide.

Influence of Mo on the microstructure and mechanical properties of TiC-based cermets

The microstructures and mechanics properties of TiC-based cermets composed of TiC, WC, Ni, Co, Mo, and Cr3C2 were investigated. The results show that Mo has a great effect on the sintering densification, microstructures, and mechanical properties. The microstructures and distribution of Mo and Ti in the TiC-based cermets were analyzed. It was indicated that a new phase with Ti, Mo, W, and C was formed on the rim of （Ti,W）C grains by means of an addition of Mo into the TiC-based cermets. The new phase with a surrounding structure was of great aid to improve the wettability of the liquid phase on the solid phase surface of TiC, decrease the porosity and refine the grains of the hard phase, which gave rise to the increase in strength and hardness. The properties of the TiC-based cermets could be further improved to some extent by adding WC, Cr2C3, and Co.

Effect of sintering atmosphere on microstructure and properties of TiC based cermets

The effect of the sintering atmospheres (vacuum, N_2, Ar) on the microstructures and properties of the TiC based cermets was studied using XRD, SEM/BSE and energy dispersive spectrometer. Compared with the alloy sintered in vacuum, the carbon content of the specimen sintered in N_2 and Ar is lower by 0.5%; and the nitrogen content is higher by 0.3% when sintered in nitrogen. The central part of the ring structure may be carbide with either a high W or Ti content. The ring structures are (Ti, W, Ta, Mo, Co, Ni)C solid solutions with different metallic elements and distributions. The composition of the binder phase is (Co, Ni) solid solution with different Ti, W, Ta, Mo, C contents. The structures are uniform for the cermets sintered in vacuum and the properties are the best. When sintered in Ar or N2, the O_2 and N2 in the atmosphere take part in the sintering reaction to break the carbon balance in the cermets to form a shell structure and defects, which results in poor density, microhardness (HV) and transverse rupture strength (TRS).

Mechanism of Combustion Synthesis of TiC-Ti Cermet

In order to investigate the mechanism of combustion synthesis of TiC-Ti cermet, a mixture of Ti and C was used for a combustion front quenching test, and the microstructural evolution in the quenched sample was analyzed by scanning electron microscopy （SEM） and energy dispersive X-ray （EDX）. Also, a temperature-time profile of the combustion reaction was measured. Based on the experimental results, a reaction-dissolution-precipitation mechanism of the combustion synthesis of TiC-Ti was proposed.

Electron-beam Treatment of Tungsten-free TiC/NiCr CermetⅡ: Structural Transformations in the Subsurface Layer

The character of structural changes in the surface layer of titanium carbide （TiC） with Ni-Cr alloy binder was investigated theoretically and experimentally after electron-beam treatment of the material surface. The thermal influence of the electron-beam irradiation on the surface layer microstructure of the composite fine-grained material was mathematically analyzed. Quantitative estimations of the depth of the zone in microstructural phase transformations were carried out. The microstructure and concentration profile of Ti distribution in the metallic binder over the cross section of the surface layer with microstructural phase transformations after electron-pulse treatment of the hard metal surface were experimentally investigated.

Electron-beam Treatment of Tungsten-free TiC/NiCr Cermet Ⅰ:Influence of Subsurface Layer Microstructure on Resistance to Wear during Cutting of Metals

An experimental investigation were performed on the effect of the impulse electron-beam irradiation upon microstruc-ture of the surface layer and on wear resistance of a cutting tool for sintered TiC/NiCr cermet. The results showed that the surface electron-beam treatment of the TiC/NiCr cermet is an efficient method for investigating the mi-crostructure and phase composition in the surface layer of the powder composite and there are optimal regimes of electron-beam treatment, which ensure a substantial increase in the resistance of the cermet to wear during cutting of metals.

Dissolution-precipitation mechanism of self-propagating high-temperature synthesis of TiC-Cu cermets

The mechanism of self-propagating high-temperature synthesis （SHS） of TiC-Cu cermets was studied using a combustion front quenching method. Microstructural evolution in the quenched sample was observed using scanning electron microscope （SEM） with energy dispersive X-ray （EDX） spectrometry, and the combustion temperature was measured. The results showed that the combustion reaction started with local formation of Ti-Cu melt and could be described with the dissolution-precipitation mechanism, namely, Ti, Cu, and C particles dissolved into the Ti-Cu solution and TiC particles precipitated in the saturated Ti-Cu-C liquid solution. The local formation of Ti-Cu melt resulted from the solid diffusion between Ti and Cu particles.

TiC Fe cermets fabricated by SHS

The dense TiC Fe cermets were produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influence of Fe content on the combustion temperature, combustion velocity, density and microstructure of products was studied. The composition and microstructure of the product were analyzed. The results showed that the cermet consists of quasi spherical TiC particles and Fe binder phases. A thin diffusion layer was found between Fe binder phase and TiC particle. In the range of 10%～20% Fe content, the combustion temperature and velocity decrease more slowly than the other contributions.

Stainless steel binder for the development of novel TiC-reinforced steel cermets

Steel reinforced TiC composites are an attractive choice for wear resistance and corrosion resistance applications. TiC- reinforced 17-4PH maraging stainless matrix composites were processed by conventional powder metallurgy （P/M）. TiC-reinforced maraging stainless steel composites with 〉97% of theoretical density were fabricated. The microstructure, mechanical and wear properties of the composites were evaluated. The microstructure of these composites consisted of spherical and semi-spherical TiC particles. A few microcracks appeared in the composites, showing the presence of tensile stress in the composites produced during sintering. Typical properties, namely, hardness and bend strength were reported for the sintered composites. After heat treatment and aging, the increase of hardness was observed. The increase of hardness was attributed to the aging reaction in the 17-4PH stainless steel. The precipitates appeared in the microstructure and were responsible for the increase in hardness. The specific wear behavior of the composites was strongly dependent on the content of TiC particles, the interparticle spacing, and the presence of hard precipitates in the binder phase.

WC与钼质量比对TiC基金属陶瓷显微组织和性能的影响

制备了WC和钼总质量分数为8%,WC与钼质量比分别为1:4,2:3,3:2,4:1的TiC基金属陶瓷,研究了WC与钼质量比对试样显微组织和性能的影响。结果表明:不同WC与钼质量比试样中的硬质相均为芯-环结构,芯相主要为TiC,环相为(Ti,M)C(M为Mo,W,V);当WC与钼质量比大于1时,黏结相中原位析出(Ti,M)C纳米颗粒;随着WC与钼质量比增加,试样的抗弯强度、断裂韧度和硬度均先增大后减小,密度增加,当WC与钼质量比为3:2时,TiC基金属陶瓷的综合性能最佳,密度较高,硬度、抗弯强度、断裂韧度最大,分别为1546 HV,1200 MPa,6.61 MPa·m^(1/2);当WC与钼质量比小于1时,弯曲时试样中的硬质相发生穿晶断裂形成解理断面,黏结相发生撕裂变形形成粗糙断面;当WC与钼质量比大于1时,纳米颗粒从黏结相中拔出形成韧窝,WC与钼质量比越大,断口上的韧窝比例越少。

Ni含量对SHS法合成TiC-Ni基金属陶瓷的影响

利用ＳＨＳ结合准热等静压（ＰＨＩＰ）技术制备了ＴｉＣ－Ｎｉ基金属陶瓷，理论分析和实验显示，绝热温度Ｔａｄ和燃烧温度Ｔｃ 随Ｎｉ含量的增加而降低，反应温度影响产物的组织形貌，Ｎｉ含量的增加使合成的ＴｉＣ颗粒尺寸变小，并且逐渐趋向于规则的球形。最后的产物均由ＴｉＣ和Ｎｉ两相组成。产物的致密度随Ｎｉ含量的增加逐渐提高，硬度值随Ｎｉ含量的变化而变化，两种因素的作用使硬度值在Ｎｉ含量为２０％ 时达到最大。

工艺参数对SHS-铸造钢基表面TiC-Fe梯度复合涂层结构的影响

将自蔓延高温合成 (SHS)技术与铸造工艺结合起来 ,制备了铸造钢基表面TiC Fe梯度复合材料 ,研究了钢液的浇注温度、Ti C Fe预制块的组成及其相对密实度等工艺参数对梯度复合涂层结构的影响。结果表明 :在保证预制块能被浇注的钢液直接点燃的条件下 ,适当提高钢液的浇注温度、降低预制块的密实度均有利于梯度复合涂层的形成 ;而且在预制块中掺加适量的低熔点金属稀释剂不仅可降低合成TiC颗粒的尺寸 ,而且也有利于梯度复合涂层的形成。梯度复合涂层的形成与钢液向预制块中的渗透。

TiC金属陶瓷/钢钎焊接头的界面结构和连接强度

采用BAg45CuZn钎料对自蔓延高温合成的TiC金属陶瓷与中碳钢进行了真空钎焊连接,利用扫描电镜、电子探针、X射线衍射等分析手段对接头的界面结构和室温抗剪强度进行了研究。结果表明,利用BAg45CuZn钎料可实现TiC金属陶瓷与中碳钢的连接;接头的界面结构为TiC金属陶瓷/(Cu,N i)固溶体/Ag基固溶体+Cu基固溶体/(Cu,N i)固溶体/(Cu,N i)+(Fe,N i)/中碳钢;在连接温度为850℃保温10 m in的钎焊条件下,接头的抗剪强度可达121 MPa。

TiC硬质合金／碳钢爆炸焊接复合板界面微观组织

用透射电镜、扫描电镜和X射线能谱仪对TiC硬质合金，碳钢爆炸焊接复合板界面微观组织和相组成进行分析。结果表明，界面上有一断续的熔合层，层厚约10μm，层内为尺寸位于几十个一几百个纳米之间的纳米或亚微米超细晶粒，组成相为铁素体、奥氏体和少量TiC。在界面附近碳钢侧可以看到明显的流线状组织特征，铁素体具有板条状马氏体的结构特征，珠光体层片间距减小，呈流线分布。焊接过程中Ti向钢中扩散15μm左右。