Pd-Ni-（Cr，V）基高温钎料对Si3N4陶瓷的润湿及界面反应

采用座滴法研究了4种钎料Pd60-Ni40,PdNi-(3-6)V,PdNi-(7-15)V和PdNi-(16-24)Cr-(6-15)V(质量分数,%)在Si3N4陶瓷上的润湿性.结果表明,在1250℃/30min的真空加热条件下,4种钎料均在Si3N4母材上润湿铺展,PdNi-(16-24)Cr-(6-15)V钎料不但润湿角小,而且形成了无缺陷的润湿界面.该钎料与Si3N4形成的扩散反应层中,Cr和V优先与从母材扩散出的N反应生成相应的Cr-N和V-N相;只有少量的Si参与反应生成相应的Cr-Si和V-si相;钎料基体区中主要是溶有少量Si的Pd-Ni固溶体以及Pd-Si和Ni-Si相.Cr相对于V更容易向界面扩散.     

WETTABILITY AND INTERFACIAL REACTIONS OF Pd-Ni-(Cr,V) BASED BRAZING FILLERS ON Si3N4 CERAMIC

采用座滴法研究了4种钎料Pd60-Ni40, PdNi-(3-6)V, PdNi-(7-15)V 和PdNi-(16-24)Cr-(6-15)V(质量分数, %)在Si3N4陶瓷上的润湿性. 结果表明, 在1250℃/30 min的真空加热条件下, 4种钎料均在Si3N4母材上润湿铺展, PdNi-(16-24)Cr-(6-15)V钎料不但润湿角小, 而且形成了无缺陷的润湿界面. 该钎料与Si3N4形成的扩散反应层中, Cr和V优先与从母材扩散出的N反应生成相应的Cr-N和V-N相;只有少量的Si参与反应生成相应的Cr-Si和V-Si相; 钎料基体区中主要是溶有少量Si的Pd-Ni固溶体以及Pd-Si和Ni-Si相. Cr相对于V更容易向界面扩散.     

采用复合钎料钎焊Si3N4陶瓷

采用TiN／Ag—Cu—Ti复合钎料连接Si3N4陶瓷材料，采用扫描电镜观察了接头组织。TiN颗粒与Ag—cu组织结合紧密，并未与钎料基体进行反应，在钎缝中分布比较均匀，形成了局部金属基复合材料组织。由于颗粒与液态钎料之间能够形成较强的毛细作用，提高了活性元素Ti扩散的能力，Ti元素能够充分扩散到钎料与母材的界面上进行反应，生成一层致密的反应层。接头抗剪强度表明，在一定范围内，采用复合钎料可以明显提高接头强度。     

采用Ag-Cu-Ti+Mo复合钎料钎焊Si3N4陶瓷

采用Ag-Cu-Ti+Mo复合钎料连接Si3N4陶瓷,利用SEM,TEM,Nanoindentation研究了钎料内钼颗粒含量对接头组织和力学性能的影响.结果表明,在Si3N4/钎料界面处形成了一层致密的反应层,该反应层由TiN和Ti5Si3组成.接头的中间部分由银基固溶体、铜基固溶体、钼颗粒和Ti-Cu金属间化合物组成.借助于纳米压痕技术测定了接头内Ti-Cu化合物以及钎料金属的弹性模量和硬度值.随着钎料内钼颗粒含量的提高,母材/钎料界面反应层厚度逐渐降低;钎料金属中Ti-Cu化合物数量增多;此外,银和铜基固溶体组织逐渐变得细小.当添加5%Mo时,得到最高的接头强度429.4 MPa,该强度相比合金钎料提高了114.7%.     

PdNi-Cr-V钎料钎焊SiC陶瓷的接头组织及性能

采用座滴法研究了PdNi-Cr-V合金钎料对SiC陶瓷的润湿性.设计的PdNi-(16-22)Cr-(7-21)V-Si-B(质量分数)钎料可用于SiC的连接,使用急冷态箔状钎料,在1190℃/10 min的连接条件下得到的接头室温三点抗弯强度平均值为84.6 MPa.微观分析表明,在靠近SiC的界面反应层中,主要是Pd和Ni优先与SiC反应生成相应的Pd-Si相、Ni-Si相和石墨;离SiC稍远的接头区域,主要是Cr和V与C和Si发生反应,生成Cr(V)-C,Cr(V)-Si,Cr(V)5Si3C等相;钎缝中心区的基体由Pd-Si,Ni-Si和V-Si相组成,其上弥散分布着块状碳化物V2C和Cr23C6.     

Ni-Fe-Cr-Ti及Co-Ni-Fe-Cr-Ti(Si,B)系高温钎料对Si3N4陶瓷的润湿与界面连接

采用座滴法研究了Ni-Fe-Cr-(14-29)Ti(质量分数,%,下同)合金在Si3N4陶瓷上的润湿行为结果表明,在1493 K,10 min的真空加热条件下,随着含Ti量的增加,合金的润湿性逐渐改善,含Ti量为24%-29%时合金的润湿角达到27.3°.微观分析表明,钎料中的元素Cr向Ni-Fe-Cr-(24-29)Ti/Si3N4界面区扩散和富集,生成了复杂的Cr-Ni-Fe-Si四元化合物.分析了Ti元素含量的增加对于合金润湿性改善的原因.合金中加入元素Co并降低Ni含量可增强Ti,Cr的活性,导致形成不同的界面反应产物并对合金润湿能力及界面结合能力产生重要影响.成分调整后的Co-Ni-Fe-Cr-(14-20)Ti合金对Si3N4的润湿角可达到20.0°,形成牢固的润湿界面.     

Ni-Mn-Si-Cu-B-Ce钎料钎焊性能的研究

为了满足在990~1010℃温度下钎焊不锈钢的需要,研究了一种Ni-Mn-Si-Cu-B-Ce钎料。对钎料的熔化特性和润湿性、接头组织以及钎焊搭接接头的剪切强度进行了研究。结果表明:微量元素B、Ce元素可使BNi66MnSiCu钎料的熔化温度显著降低,从而满足在990~1010℃温度下钎焊不锈钢,加入微量元素B、Ce元素后使钎料对1Cr18Ni9Ti不锈钢的润湿性影响较小,但钎料的剪切强度提高约133倍,利用Ni-Mn-Si-Cu-B-Ce钎料在钎焊1Cr18Ni9Ti不锈钢后,发生了互扩散效应,钎料与母材之间形成了牢固的扩散层;在Ni-Mn-Si-Cu-B-Ce钎料显微组织中,主要存在Ni基固溶体(溶解有微量的Cu)以及Cu_9Si、MnSi、Mn_6Ni_(16)Si_4等化合物相。     

合金元素对Ti-Ni-Cu系钎料性能的影响

本实验设计一系列不同成分的Ti-Ni-Cu系钎料,研究合金元素B、Si、Zr等对钎料非晶形成能力和性能的影响.结果表明:微量B、Si元素均能显著改善Ti-Ni-Cu系钎料对Si3N4陶瓷的润湿性;在相同试验条件下,添加0.2%B的Ti40Ni15Cu钎料铺展面积最大;不含zr元素的Ti-Ni-Cu系钎料合金的非晶形成能力均很差.本实验设计的Ti40Zr20Ni20CuB0.2、Ti40Zr20Ni25CuB0.2两种钎料既具有良好的润湿性,又具有良好的非晶形成能力;与Ti40Zr25Ni15Cu非晶钎料钎焊Si3N4陶瓷的接头相比,Ti40Zr20Ni20CuB0.2、Ti40Zr20Ni25CuB0.2非晶钎料钎焊Si3N4陶瓷接头的室温强度变化不大,但高温强度有明显提高.     

用非晶钎料加铜层连接Si3N4的界面结构与强度

采用TiZrCuB非晶钎料和铜箔中间层连接Si3N4陶瓷,研究了钎料成分和铜箔厚度对接头界面结构和抗弯强度的影响.结果表明,采用Ti40Zr25CuB0.2非晶钎料和70!m铜箔中间层,在1 323 K×30 min和0.027 MPa压力下连接Si3N4陶瓷,其接头抗弯强度最高为241 MPa;Si3N4陶瓷连接接头界面反应层为TiN,界面微观结构为Si3N4/TiN/Ti-Si+α-Cu+Ti-Zr+Cu-Zr;改变中间层厚度可以调整反应层的结构和厚度;随铜箔厚度增加,Ti-Si化合物层逐渐脱离TiN层被推向钎缝中心并细化呈颗粒状.     

CuSiAlTi钎料对SiC陶瓷的润湿性

研究了CuSiAlTi钎料对SiC陶瓷的润湿性。发现元素Ti显著影响钎料对SiC陶瓷的润湿性。采用SEM，XRD对润湿界面进行了观察分析，发现在界面上存在1个含TiC的很薄的界面层和含Cu较多、含Ti元素较少的较厚的界面过渡层。分析表明，在润湿过程中钎料中的元素与SiC陶瓷中的Si，C相互扩散，Cu元素在SiC陶瓷一侧是主要的扩散元素，Cu的扩散在SiC陶瓷一侧形成了较厚的扩散层。     

Properties and fracture processes of Si3N4/ Si3N4 joints brazed using Cu–Zn–Ti filler alloy

Abstract

Si₃N₄ ceramic was jointed to itself using a filler alloy of Cu-Zn-Ti at 1123-1323 K for 0.3-2.7 ks. Ti content in the Cu-Zn-Ti filler alloy was varied from 5 to 20 at.-%. The effect of brazing parameters, such as brazing temperature, holding time and Ti content, on the mechanical properties and facture processes of the Si₃N₄/Si₃N₄ joint were investigated. The results indicated that the increased brazing temperature, holding time and Ti content increase the thickness of the interfacial reaction zone in the Si₃N₄/filler alloy, and the size and amount of the reaction phases in the filler alloy. Their increases lead to increasing shear strength of the joint. The fracture behaviour of the Si₃N₄/Si₃N₄ joint greatly depends on the microstructure of the joint. A suitable thick reaction zone with reaction phases yields the high strength of the Si₃N₄/ Si₃N₄ joint.     

Microstructure evolution of the Si3N4/Si3N4 joints brazed using Au-Ni-V filler alloys with different V content

Au-Ni-V filler alloys with different vanadium contents were designed to braze Si₃N₄ ceramic at 1373 K for 30 min, and the microstructures of brazing seams were investigated by SEM and TEM. When the Au-Ni-V filler alloy contains 5 at.% V, round-like Ni[Si, V, Au] precipitates form in the Au[Ni] solid solution matrix and a VN reaction layer with 0.5 μm thickness appears on Si₃N₄ interface. When the V content increases to 10 at.%, a new polygonal Ni₂SiV₃ phase occurs in the seam, and the Ni[Si, V, Au] precipitate coarsens and VN layer thickens. With increase of V contents to 15 and 20 at.%, laminar Ni[Au] and polygonal Ni₃V precipitates form. With 25 at.% V content in the filler alloy, the Ni₂SiV₃ and Ni₃V precipitates distribute homogenously in the brazing seam. These microstructure evolutions were attributed to the reaction between Si₃N₄ and vanadium, which forms VN reaction layer and releases Si into the molten alloy.     

SiC纳米线对Ni-Cr-P钎料及Ni-Cr-P/Q235焊点组织与性能影响

采用具有优良高温强度、高热导率、高耐磨性能和耐腐蚀性能的SiC纳米线为Ni-Cr-P钎料的添加物,研究了钎料/焊点的组织与性能。结果表明,钎料的组织由Ni(Cr)固溶体、Ni₃P固溶体以及Ni(Cr)和Ni₃P共晶组织组成,微量的SiC纳米线可以显著细化基体组织,使焊点抗剪切强度提高29.6%。SiC纳米线的添加使钎料的熔化温度提高约4℃,显著促进钎料在Q235基板表面的润湿性,增幅达到12.5%。然而,过量添加SiC纳米线会显著粗化基体组织,降低钎料的润湿性和焊点的抗剪切强度。在不同SiC含量的Ni-Cr-P钎料中,Ni-Cr-P-0.1SiC钎料/焊点具有明显的优越性。     

Experimental isothermal section at 1200 °C of V–Cr–Si system

In the present work, the isothermal section at 1200 °C of the V–Cr–Si phase diagram was experimentally studied. The samples were prepared by arc melting and characterized using scanning electron microscopy/energy-dispersive spectroscopy and electron probe microanalyzer. The continuous solution phases (Cr,V)₃Si, (Cr,V)₅Si₃ and (Cr,V)Si₂ were confirmed. The solubilities of Cr in V₆Si₅ and of V in CrSi have been measured. A ternary phase (Cr,V)₁₁Si₈ was observed and its homogeneity range, which is at constant Si ratio, was determined at 1200 °C.     

Brazing Si3N4 ceramic to AISI 5140 steel under pressure

Pressures (0 to 40 MPa) were applied to the joints of Si₃N₄ ceramic to 5140 steel during vacuum brazing with Ag-Cu-Ti active filler metal. Pressurization started at various temperatures (873,973, and 1073 K) and ended at room temperature during cooling. Results show that there is an optimum starting temperature to pressurize, at which the maximum room temperature shear strength of the joint is obtained.     

Thermal stability and oxidation resistance of laser clad TiVCrAlSi high entropy alloy coatings on Ti-6Al-4V alloy

TiVCrAlSi high entropy alloy coatings were deposited on Ti-6Al-4V alloy by laser cladding. SEM, XRD and EDS analyses show that, the as-clad coating is composed of (Ti,V)₅Si₃ and a BCC solid solution. After annealing at 800 °C for 24 h under vacuum, the coating is composed of (Ti,V)₅Si₃, Al₈(V,Cr)₅, and a BCC solid solution. The temperature-dependent phase equilibrium for the coating material calculated by using the CALPHAD method, indicates that above 880 °C the stable phases existing in the coating material are a BCC solid-solution and (Ti,V)₅Si₃. When the temperature is below 880 °C, the stable phases are (Ti,V)₅Si₃, Al₈(V,Cr)₅, and a BCC solid solution. In order to validate the calculation results, they were compared with TiVCrAlSi alloy samples prepared by arc melting, encapsulated in quartz tubes under vacuum, annealed at 400-1100 °C for 3 days and water-quenched. XRD analysis shows that the experimental phase composition agrees with the thermodynamic calculations. After vacuum annealing, there is a small increase of hardness for the laser clad TiVCrAlSi coating, which is due to the formation of Al₈(V,Cr)₅. The oxidation tests show that the TiVCrAlSi coating effectively improves the oxidation resistance of Ti-6Al-4V at 800 °C in air. The formation of a dense and adherent scale consisting of SiO₂, Cr₂O₃, TiO₂, Al₂O₃ and a small amount of V₂O₅ is supposed to be responsible for the observed improvement of the oxidation resistance.     

The oxidation of cobalt based alloys containing partially dissolved particles of Si3N4 at 1000°C

The isothermal oxidation behavior of Co-Cr and Co-Cr-Si alloys with and without 5, 10, and 15 vol.% dispersions of unstable Si₃N₄ particles was studied in 1 atm of oxygen at 1000°C. The dispersion of Si₃N₄ which dissolved partially in the matrix, greatly reduced the oxidation rate of Co-Cr alloys. Silicon nitride was found to promote the formation of continuous Cr₂O₃ layers at low chromium concentrations. Furthermore, the unstable Si₃N₄ was more effective in reducing the oxidation rate than an alloy containing an equivalent amount of silicon. Additions of 15vol.% Si₃N₄ tended to increase the oxidation rate by forming nonprotective SiO₂ particles which disrupted the protective Cr₂O₃ scale. The mechanism of oxidation was altered due to the Si₃N₄ additions. Marker experiments indicated oxygen diffusion inward via the CoO lattice, rather than a combination of both oxygen and metal ion motion which is encountered in Co-Cr alloys.     

Interfacial behavior in the brazing of silicon nitride joint using a Nb-foil interlayer

Silicon nitride (Si₃N₄) samples prepared the spark plasma sintering (SPS) technique, which had different amounts of oxide additives, were used as disc-preforms. The surfaces of the materials to be bonded during the brazing process (ceramic, metal and filler alloys) were previously coated with thin layer of silver and then stacked together with these preforms. Sandwich-like specimens of Si₃N₄/Cu–Zn/Nb/Cu–Zn/AISI-304 combinations were joined at 1000 °C using 5, 20, and 40 min holding times under an inert atmosphere. Analysis by scanning electron microscopy revealed un-joined zones between the ceramic and metallic parts after 5 min of treatment. For holding times >20 min, homogenous and non-porous Si₃N₄/Cu–Zn/Nb interfaces were obtained. The thicknesses of the resulting ceramic–metal interfaces increased from ～10 to >25 μm as the holding time was increased. The amount of additives used during the preparation of the Si₃N₄ ceramics had a direct effect on the decomposition rate of Si₃N₄ during the joining process. The largest decomposition of Si₃N₄ was observed at 1000 °C/40 min from the less dense ceramic preforms (4 wt% of additives in this case), which in turn induced the migration of Si atoms through the interface to promote the formation of Si-based components. In contrast, when using larger amounts of additives (8 wt%) during sintering of the ceramic performs, it becomes more difficult for N and Si to dissociate upon brazing. When the diffusion rate of Si is low, it migrates toward the metal part, which limits the formation of Si-based components.     

过氧化氢环境下1Cr18Ni9Ti不锈钢与不同陶瓷配副的摩擦学行为

本文研究了ZrO_2, Si₃N₄ 和SiC三种陶瓷配副对1Cr18Ni9Ti不锈钢在90%的H₂O₂溶液中摩擦学性能的影响。结果表明,1Cr18Ni9Ti不锈钢在该环境下的摩擦学性能受配副的影响明显。 与ZrO₂对磨,发生了粘着行为,导致了大的摩擦系数(0.17~0.27)和最高的1Cr18Ni9Ti不锈钢磨损量。与SiC对磨,发生了氧化和水解反应,形成的胶体膜起到了润滑作用,导致了小的摩擦系数(0.035)和最低的1Cr18Ni9Ti不锈钢磨损量。粘着行为和水解反应均发生于1Cr18Ni9Ti/Si₃N₄的磨损过程中,粘着与保护膜的耦合,导致了复杂的摩擦系数。对于配副,ZrO₂的磨损体积最大,SiC次之,Si₃N₄表面有粘着层,因此磨损体积最小。     

Deposition and characterization of CrN/Si3N4 and CrAlN/Si3N4 nanocomposite coatings prepared using reactive DC unbalanced magnetron sputtering

Nanocomposite coatings of CrN/Si₃N₄ and CrAlN/Si₃N₄ with varying silicon contents were synthesized using a reactive direct current (DC) unbalanced magnetron sputtering system. The Cr and CrAl targets were sputtered using a DC power supply and the Si target was sputtered using an asymmetric bipolar-pulsed DC power supply, in Ar + N₂ plasma. The coatings were approximately 1.5 μm thick and were characterized using X-ray diffraction (XRD), nanoindentation, X-ray photoelectron spectroscopy and atomic force microscopy. Both the CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings exhibited cubic B1 NaCl structure in the XRD data, at low silicon contents (< 9 at.%). A maximum hardness and elastic modulus of 29 and 305 GPa, respectively were obtained from the nanoindentation data for CrN/Si₃N₄ nanocomposite coatings, at a silicon content of 7.5 at.%. (cf., 24 and 285 GPa, respectively for CrN). The hardness and elastic modulus decreased significantly with further increase in silicon content. CrAlN/Si₃N₄ nanocomposite coatings exhibited a hardness and elastic modulus of 32 and 305 GPa, respectively at a silicon content of 7.5 at.% (cf., 31 and 298 GPa, respectively for CrAlN). The thermal stability of the coatings was studied by heating the coatings in air for 30 min in the temperature range of 400-900 °C. The microstructural changes as a result of heating were studied using micro-Raman spectroscopy. The Raman data of the heat-treated coatings in air indicated that CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings, with a silicon content of approximately 7.5 at.% were thermally stable up to 700 and 900 °C, respectively.