激光熔覆Ni包WC复合涂层的组织、耐磨和耐蚀性分析及应用

对45钢基体进行激光熔覆Ni包WC金属陶瓷涂层强化处理,通过X射线衍射(XRD)、扫描电子显微镜-能谱分析(SEM-EDX)和透射电子显微镜(TEM),研究了激光熔履Ni包WC涂层的显微组织和物相组成,并采用摩擦磨损试验和电化学测试系统研究了Ni包WC涂层的摩擦磨损性能和耐蚀性能.结果表明,在激光熔覆Ni包WC金属陶瓷...     

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。     

烧结温度对Al_2O_3 WC陶瓷强韧性的影响

采用不同常压烧结（CP）温度制备了Al2O3＋WC复合陶瓷材料。利用扫描电镜（SEM）、X一射线衍射、能谱分析（EDAX）等手段和三点弯曲、单边切口梁等力学方法研究了该材料的组织结构、力学性能及增韧机制。结果表明,1600℃烧结Al2O3＋WC陶瓷各相结合致密、分布均匀且晶粒微细,其断裂形式为沿晶断裂;室温断裂强度为520MPa;断裂韧性为6.2MPa·m1／2;第二相WC弥散分布细化了基本晶粒,韧化机制主要为裂纹弯曲偏转韧化。     

SiC组分含量对SiC/Cu复合材料力学性能的影响

采用真空热压法制备了不同配比的SiC/Cu金属陶瓷复合材料.利用阿基米德原理测定了复合材料的密度及气孔率;利用Instron万能材料电子试验机测得其三点弯曲强度;采用Hv-1000显微硬度仪测试其显微硬度,采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对烧成样品的物相组成和断口显微形貌进行表征.结果表明:随着SiC组分含量的增加,SiC/Cu复合材料的致密度、抗弯强度均有所下降,而气孔率和显微硬度显著增加.在750 ℃,30 MPa压力作用下,保温3 min,制备得到的30SiC/70Cu(vol%)的复合材料,具有最优的力学性能,其显微硬度达到2087.2 MPa,抗弯强度为174.0 MPa.SiC/Cu复合材料的断裂行为既表现出一定的微观韧性特征,又表现出一定的脆性特征.     

掺加WC／Co对B4C材料烧结行为的研究

在B4C基体中掺加不同含量的WC/Co(其中WC为94%,Co为6%),利用WC/Co的易烧结性,在不同温度热压烧结B4C,得到了高致密度的复合材料.通过实验发现,随着温度和WC/Co含量的提高,材料的密度增大.当WC/Co的含量达到40%(体积分数)时,在1900℃×30min×35MPa的条件下,复合材料的相对密度＞98%.1500℃以上时,WC/Co作为液相的出现,促进了B4C的固相烧结,是材料获得高致密度的主要原因.利用XRD、SEM分析了复合材料的物相组成及显微组织.研究了不同含量的WC/Co对复合材料致密度的影响.     

TiO2对R2O-MgO-Al2O3-SiO2-ZrO2系微晶玻璃析晶及性能的影响

以花岗岩废渣为主要原料,用熔融法制备了添加TiO2的R2O-MgO-Al2 O3-SiO2-ZrO2(RMASZ)系微晶玻璃.采用X-射线衍射(XRD)、扫描电子显微镜(SEM)、电子万能材料试验机和显微硬度测试仪研究了TiO2对RMASZ系微晶玻璃的晶相组成、显微结构以及力学性能的影响.结果表明:当TiO2含量为0wt％、0.5wt％、1wt％时析出的主晶相为t-ZrO2和顽火辉石;当TiO2含量为2wt％和3wt％时析出假蓝宝石相,顽火辉石相减少.当TiO2为0.5wt％时晶粒细致均匀,其四点抗弯强度达到122.41 MPa,显微硬度为9.35 GPa.     

Cr含量对Mo2FeB2基金属陶瓷组织和性能的影响

采用真空液相烧结法制备了Mo2FeB2基金属陶瓷,研究了Cr添加量(质量分数0～11％)对其组织和力学性能的影响.结果表明:Cr的添加使金属陶瓷出现Fe23B相,Cr完全固溶于Fe基粘结相中;随着Cr添加,硬质相晶粒逐渐由柱状晶向等轴晶转变;当Cr添加量为9％时,金属陶瓷的孔隙率最小,致密度最高,当Cr添加量大于9％时...     

花岗岩废渣微晶玻璃晶化工艺研究

用差示扫描量热法(DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)等测试方法研究了晶化工艺对R_2O-CaO-MgO-Al_2O_3-SiO_2-F系废渣微晶玻璃晶相组成、显微结构和力学性能的影响。结果表明:873℃晶化1 h,试样主晶相为斜顽辉石;随着晶化温度升高斜顽辉石向透辉石转变,1010℃晶化1 h,试样主晶相为透辉石和斜顽辉石,三点抗弯强度和显微硬度达最大值,分别为125 MPa、5.21 GPa;1 080℃晶化1 h,出现氟闪石新相,力学性能开始下降。     

金属-陶瓷复合涂层的组织与磨损性能研究

利用等离子喷涂方法制备出Ni60+Ni/WC金属陶瓷复合涂层,分析了复合涂层的微观组织,采用自行设计并制造的多用磨损试验机,研究了金属陶瓷复合涂层的磨损性能。研究发现加入适量的Ni/WC,可以提高涂层的耐磨性,复合涂层磨损失效形式为微观切削、犁沟塑性变形、微观断裂(剥落)磨损和疲劳磨损机理。     

不同烧结温度制备的双相磷酸钙生物陶瓷及其力学性能研究

以煅烧缺钙磷灰石制备的双相磷酸钙(BCP)粉体为原料,采用热压烧结的方法制备了一种可用于骨替代、力学性能优良的生物陶瓷材料.研究了烧结温度对BCP陶瓷力学性能、物相组成和微观形貌的影响.当烧结温度为1100℃和1150℃时,BCP陶瓷的物相组成为HA和β-TCP,断裂方式以穿晶断裂为主;当烧结温度为1200℃时,BCP陶瓷的物相组成为HA和α-TCP,断裂方式为穿晶和沿晶混合断裂模式.当烧结温度为1150℃时,BCP陶瓷的弯曲强度和断裂韧性最高,分别为98 MPa和0.99 MPa·m1/2.     

Influence of molybdenum addition on the microstructure and mechanical properties of TiC-based cermets with nano-TiN modification

Effect of Mo addition on the microstructure and mechanical properties of TiC–TiN(nm)–WC–Co–Ni–C system cermets was studied in the work. Specimens were fabricated by conventional powder metallurgy techniques. The microstructure was investigated using transmission electron microscope (TEM) and the scanning electron microscope (SEM). Chemical compositions of different phases such as ceramic phase with core/rim structure [the core being TiC and rim being (Ti,W,Mo)(C,N)] and metallic phase were analyzed quantitatively by EDX. Mechanical properties such as flexural strength, fracture toughness and hardness were also measured. Results show that flexural strength and fracture toughness have a trend to decline with increasing Mo addition, but the change of hardness is not apparent with the increase of Mo addition. Results also reveal that finer microstructure and thicker rim phase will be obtained with the increase of Mo addition. The optimal addition of Mo can be estimated to be 4 wt.% with respect to TiC–10TiN(nm)–15WC–5Co–Mo–5Ni–1C system cermets. Fracture micrographs show that main failure mode of the cermets is a mixed one, i.e., trans-granular and inter-granular fractures both exist.     

Effects of TiC/TiN addition on the microstructure and mechanical properties of ultra-fine grade Ti (C, N)–Ni cermets

Two series of Ti (C, N)-based cermets, one with TiC addition and the other with TiN addition, were fabricated by conventional powder metallurgy technique. The initial powder particle size of the main hard phase components (Ti (C, N), TiC and TiN) was nano/submicron-sized, in order to achieve an ultra-fine grade final microstructure. The TiC and TiN addition can improve the mechanical properties of Ti (C, N)-based cermets to some degree. Ultra-fine grade Ti (C, N)-based cermets present a typical core/rim (black core and grayish rim) as well as a new kind of bright core and grayish rim structure. The average metallic constituent of this bright core is determined to be 62 at% Ti, 25 at% Mo, and 13 at% W by SEM–EDX. The bright core structure is believed to be formed during the solid state sintering stage, as extremely small Ti (C, N)/TiC/TiN particles are completely consumed by surrounding large WC and Mo₂C particles. Low carbon activity in the binder phase will result in the formation (Ni₂Mo₂W)C_x intermetallic phase, and the presence of this phase plays a very important role in determining the mechanical properties of TiN addition cermets.     

Assessment of mechanical properties at microstructural length scale of Ti(C,N)–FeNi ceramic-metal composites by means of massive nanoindentation and statistical analysis

It is well known the interest of the scientific community in substituting the traditional cemented carbides (WC–Co) by alternative ceramic-metal systems. In this regard, Ti(C,N)-based cermets arise as excellent candidates due to their exceptional mechanical, tribological and thermal properties. In this work, microstructurally different Ti(C,N)–FeNi cermets were processed using a combination of colloidal and powder metallurgy techniques. Three distinct ceramic/metal phase ratios were used: 85/15, 80/20 and 70/30 (volume fraction) of Ti(C,N) and FeNi respectively. Microstructural parameters and micromechanical properties (hardness and stiffness) of the three composite systems and their constitutive phases were assessed. Small-scale hardness was evaluated by means of massive nanoindentation testing and statistical analysis of the gathered data, under the consideration of three mechanically different phases: Ti(C,N) particles, metallic binder and a composite-like one, corresponding to probing regions containing both constitutive phases. It is found that values of local hardness for both composite-like and metallic phases increase as the ceramic/metal phase ratio rises. In particular, local hardness values are determined to be significantly distinct for the metallic binder in the three cermets investigated. Results are discussed and rationalized on the basis of the constrained deformation imposed for the harder phase to the softer and more ductile one. Estimated effective flow stress values for the metallic binder as well as detailed inspection of crack-microstructure interaction and fractographic features point out the effectiveness of FeNi as reinforcement phase and toughening agent for Ti(C,N)-base cermets.     

Effect of powder size on microstructure and mechanical properties of Ti(C,N) based cermets

Abstract

Effect of the particle size of TiC and TiN on the microstructure and mechanical properties of Ti(C,N) based cermets has been evaluated. Ti(C,N)–WC–Co cermets made from four groups of mixed raw powders of different sizes were manufactured by vacuum sintering. The microstructure and composition were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDX). The result shows that the four samples have the typical microstructures of 'black core/grey rim'. The mechanical properties of the cermet manufactured from submicron TiC and nano TiN are the best among the four samples.     

Micropillar compression of Ti(C,N)-FeNi cermets: Microstructural,processing, and scale effects

The influence of microstructure and processing route on the small-scale mechanical response as well as on the deformation and failure mechanisms of Ti(C,N)-FeNi cermets were investigated by uniaxial compression of micropillars milled by focused ion beam with different sizes. Stress-strain curves were determined and associated deformation mechanisms were observed in-situ using scanning electron microscopy. The appropriate micropillars dimension was assessed, based on the microstructural characteristics of studied cermets, to overcome scale effect issues. A direct relationship was observed between yield strength and ceramic/metal ratio for colloidal samples. Meanwhile, deformation of metallic binder and glide between Ti(C,N)/Ti(C,N) particles were evidenced as dominant mechanisms during the compression for colloidal cermets with 70 and 80 vol% of ceramic phase, respectively. The obtained results illustrate that samples processed from powder attained by colloidal route provide superior mechanical behavior, as compared to that exhibited by specimens shaped following a conventional powder metallurgy one (wet ball-milling/drying).     

Fabrication of Ti(C,N)‐based cermets by in situ carbothermal reduction of MoO3 and subsequent liquid sintering

Ti(C,N)‐based cermets were fabricated by in situ carbothermal reduction of MoO₃ and subsequent liquid sintering in a single heating process. The densification behavior, phase formation, and microstructure evolution of the cermets were characterized by DSC, XRD, SEM, and TEM. The results showed that near‐fully dense Ti(C,N)‐based cermets with fine carbonitride grains could be obtained by the above‐mentioned method. The carbonitride grains of the cermets still exhibited typical core/rim structures and evenly distributed in the binder phase, but the rim phase was more complete and thinner compared with traditional cermets. In addition, the interfaces between the ceramic phase and binder phase of the cermets were atomically smooth, having the orientation relationship of ()_R//(110)_B with a perfect coherency state. The prepared Ti(C,N)‐based cermets produced with MoO₃ showed excellent comprehensive mechanical properties having a transverse rupture strength of 2461±62 MPa, a Rockwell hardness of 88.0±0.1 HRA, and a fracture toughness of 22.3±0.4 MPa·m^1/2, respectively.     

Effects of particulate metallic phase on microstructure and mechanical properties of carbide reinforced alumina ceramic tool materials

Alumina-based composite ceramic tool materials reinforced with carbide particles were fabricated by the hot-pressing technology. Choice of metallic phase added into the present composite ceramic was based on the distribution of residual stress in the composite. The effects of metallic phase on microstructure and mechanical properties of composites were investigated. The metallic phase could dramatically improve room temperature mechanical properties by refining microstructure, filling pores and enhancing interfacial bonding strength. However, it also led to sharp strength degradation at high temperature because the metallic phase was easier to be oxidized and get soft at high temperature in air. The effects of metallic phase on strengthening and toughening were discussed. The improved fracture toughness of composite with metallic phase was attributed to the lower residual tensile stress in the matrix and the interaction of more effective energy consuming mechanisms, such as crack bridged by particle, crack deflection and intragranular grain failure.     

Microstructure,interfacial characteristics,and wear performances of Cu–Fe–SiC cermet composites

The Cu–Fe metal-based ceramic grinding wheel material with SiC as abrasive was prepared by the powder metallurgy process of ball milling and hot pressing sintering. Cu–Fe–SiC cermets with Cu:Fe mass ratios of 4:1, 1:1, and 1:4 were designed by changing the composition of metal binder. The phase composition, microstructure, mechanical properties, and grinding properties of Cu–Fe–SiC cermets were systematically studied. The effect of Cu–Fe binder ratio on the microstructure and properties of cermets was analyzed. The results show that with the increase of Fe content, the density and hardness of cermets increase gradually, indicating that the mechanical properties are improved. Because the Fe in the adhesive can react with the abrasive SiC to form the reaction bonding interface, the Cu–80Fe–SiC cermets with higher Fe content have better adherence. The grinding test results of Cu–80Fe–SiC cermet show that the friction coefficient is .341, the surface roughness is 6.64 μm, the residual stresses parallel to the grinding direction are 353.3 MPa, and the residual stresses perpendicular to the grinding direction are 140.9 MPa. With the increase of Fe content, the wear mechanism changes from ploughing and cutting to friction.     

Carburization and wear behavior of self-lubricating Ti(C,N)-based cermets with various secondary carbides

Self-lubricating Ti(C,N)-based cermets were manufactured using vacuum sintering and solid carburizing in this study, and the effects of various carbides on the carburization and wear behavior of the cermets were investigated. The findings demonstrate that solid carburizing resulted in strong graphite precipitation in all the Ti(C,N)-based matrices. Refractory carbides significantly affect the morphological characteristics of graphite in cermets. The activated carbon atoms in the cermet matrix are consumed in two ways: rearrangement followed by precipitation in the form of graphite and combination with metal atoms followed by precipitation in the form of carbides or carbonitrides. As the amount of refractory carbide dissolved in the binder phase increases, more carbon atoms are consumed by bonding with metal atoms, and less graphite is precipitated. The precipitation of carbides and carbonitrides in the ceramic phase increases the rim phase thickness. After carburization, the mechanical properties of the cermets were noticeably degraded owing to the introduction of graphite and the coarsening of ceramic particles. However, the presence of graphite significantly reduced the friction coefficient of the cermet material owing to its good lubrication effect. The decreased mass loss and better wear morphology suggest that the wear deterioration of all the cermets is remarkably mitigated by carburization. The wear properties of cermets are determined by the mechanical properties and the lubrication conditions of the contact surfaces, and good lubrication conditions can partially compensate for the degradation of the mechanical properties of cermets in the sliding wear process.     

Effect of the Cubic Phase Distribution on Ultrafine WC–10Co–0.5Cr–xTa Cemented Carbide

The (Ta, W)C cubic phase distribution plays a key role in the microstructure and mechanical properties of ultrafine WC–Co–Cr₃C₂–TaC cemented carbides. By integration of thermodynamic calculations and key experiments, the influence of the cubic phase distribution in ultrafine WC–10Co–0.5Cr–xTa cemented carbides was systematically investigated. A series of ultrafine grained cemented carbides were designed and fabricated through ball‐milling and vacuum sintering at 1410°C for 1 h. The microstructure was investigated using scanning electron microscopy (SEM). The electron backscattered diffraction (EBSD) was used to measure the orientation and size of cubic phase segregation. The results indicate that the cubic phase in the microstructure distributes more heterogeneously in the range of 0.2 to 0.7 wt% Ta addition, but finally the isolated cubic phase is homogeneously distributed with a Ta content from 0.7 to 1 wt%. Combining the thermodynamic calculation with the experiment, the mechanism for the microstructure evolution has been revealed. The mechanical properties of alloys substantially depend on the cubic phase distribution in the microstructure. A synergetic correlation between the transverse rupture strength (TRS) and Rockwell hardness was observed. The homogeneity of cubic phase can be designed and controlled effectively via the present approach.