Partial Transient Liquid Phase Research Articles

Partial transient liquid phase bonding of misoriented single crystal superalloys via a mixture of nickel-chromium-tantalum and nickel-based superalloy powders

In order to realize high-performance joining of misoriented single crystal superalloys, a rapid partial transient liquid phase (PTLP) bonding process was proposed in this work. By using a mixture of nickel-chromium-tantalum (Ni-Cr-Ta) and nickel-based superalloy (FGH4096) powders as filler material, high-performance PTLP joints of misoriented single crystal superalloys (DD5) were obtained. The joint bonded at 1260 °C consisted of an epitaxial growth zone (EGZ) containing γ/γ' derived from DD5 and a polycrystalline zone (PCZ) located at the center of the joining layer, in which tantalum dichromide (TaCr2) and tantalum carbide (TaC) existed at the grain boundaries. As the Ni-Cr-Ta content increased, the voids in the joints decreased while the Ta-rich compounds increased and the grain size decreased. With the holding time increasing, the Ta-rich compounds decreased while the grain size increasing. The optimum process was 60 min at 1260℃ with the Ni-Cr-Ta content of 60 wt%. Due to the specially designed filler metal without boron (B) and silicon (Si) elements, there was no low-melting eutectic or compound in the PTLP joints, which ensure the joint with high-performance at elevated temperatures. Compared with transient liquid phase (TLP) bonding process, the PTLP bonding process achieved rapid isothermal solidification with the help of the short-distance and large-area diffusion mechanism between the Ni-Cr-Ta (liquid phase) and FGH4096/DD5. The presence of PCZ prevented the formation of penetrating grain boundary, and thus eliminated the effect of misorientation between two base metals on the performance of the joints. The tensile strengths at room temperature and 980 °C of the PTLP joints which obtained with the optimum process were 926.05 MPa and 681.96 MPa, respectively, up to 90.32% and 92.25% of the base metal. The PTLP bonding process proposed in the present work may provide a high efficiency approach to achieve high-performance single crystal superalloy joint, which is also gifted a major advantage of B/Si-free.

Rapidly achieving high-performance joining of single crystal superalloy and powder metallurgy superalloy via partial transient liquid phase diffusion bonding

A rapid and high-performance partial transient liquid phase diffusion bonding process has been proposed for the DD5 single crystal superalloy and the FGH96 P/M superalloy via a mixture of NiTi alloy and FGH96 P/M superalloy powders as interlayer. During the bonding process, isothermal solidification and homogenization of the joint were achieved through a rapid diffusion mechanism of short-range and large-area between the liquid phase of NiTi and the FGH96 particles and the base material. When bonded at 1170 °C only for 60 min of the holding time, isothermal solidification and homogenization of the joints were completed. The isothermal solidification joint consisted of a polycrystalline zone with γ/γ′ structure similar to that of FGH96 and an epitaxial growth zone (EGZ) derived from DD5. Compared with traditional brazing and transient liquid diffusion bonding process (TLP), no brittle compounds and eutectics of Si and B were presented in the joint, which ensured the joint with excellent mechanical properties. With the increase of holding time, both the tensile strength and elongation was significantly increased on account of the reduction of η-Ni3Ti. When the joints were bonded at 1170 °C for 60 min, the elevated temperature strength of 650 °C reached 880.7 MPa, which was more than 80 % and 60 %o that of the DD5 and FGH96, respectively.

Ti/Cu/Kovar Multilayer Interlayer PTLP Diffusion Bonding Si3N4/Ht250

In this paper, partial transient liquid phase (PTLP) diffusion bonding between Si3N4 ceramics and Ht250 cast iron was carried out by using an Ti/Cu/Kovar/Cu/Ti interlayer. The effects of the heating temperature and holding time on the microstructure, formation mechanism, and mechanical properties of Si3N4/Ht250 cast iron joints were studied. The results show that the maximum shear strength of the joint is 112 MPa when the welding temperature is 1000 °C and the holding time is 1 h. In addition, the problems of Ti/Cu/Ti intermetallic compound formation and Cu/Si3N4 ceramic residual thermal stress in the joint can be effectively alleviated.

Partial transient liquid phase diffusion bonding of ZrC-SiC and 304 stainless steel by Ti/Ni interlayer: Microstructure and properties

The ZrC-SiC ceramic (ZS) was joined to 304 stainless steel (304SS) by using Ti/Ni interlayer. The joining process involves a transient liquid phase bonding at the ZS interface and a diffusion bonding at the 304SS interface. It is found TiCx grew fast on ZS interface or precipitated as particles in certain region of transient liquid, and its distribution and morphology were controlled by Ti gradient. Small amount of Si dissolved into liquid and then precipitated as Ti3Ni2Si with similar lattice structure to Ti2Ni. During solid-state diffusion, the TiNi reaction layer quickly transformed to refractory TiNi3 layer with a small number of Kirkendall pores and Ni5Zr phase at the TiNi3/Ni boundary. The underlying mechanism of interfacial reactions and microstructure evolution were proposed. The maximum shear strength of 97 ± 10 MPa was achieved when joining at 960 °C for 3 h. The failure mainly occurred along TiNi3/Ni boundary due to the presence of Kirkendall pores.

Interlayer design for partial transient liquid phase bonding of titanium and copper

Abstract Partial transient liquid phase (PTLP) bonding of Ti and Cu at 900 °C using Ti–Zr–Ni/Mo/Ag–Cu–Ti assembled interlayers was investigated. Active brazing took place at the Cu/Ag–Cu–Ti/Mo half, leading to intermetallic compound (IMC) free joint with robust interfacial bonding. Transient liquid phase (TLP) bonding took place at the Mo/Ti–Zr–Ni/Ti half. IMCs segregated at the Mo/Ti–Zr–Ni/Ti interface at initial stage, leading to poor joint strength. Such IMCs can be eliminated upon homogenization with prolonged exposure up to 20 min at high temperature. The homogenized joint free from blocky IMCs exhibited bonding strength (210 MPa) comparable with Cu substrate properties.

A novel process with the characteristics of low-temperature bonding and high-temperature resisting for joining Cf/SiC composite to GH3044 alloy

Taking advantages of reaction composite brazing, transient liquid phase bonding (TLP) and partial transient liquid phase bonding (PTLP), a novel process with the characteristics of low-temperature bonding and high-temperature resisting was developed for joining Cf/SiC composite to GH3044 alloy by using (Cu-Ti) + C + Ni mixed powder filler. Under the bonding temperature (980 °C), the reaction between the liquid Cu-Ti alloy and C particles (reaction composite mechanism), composition homogenizations between the joining layer and Ni particles (PTLP mechanism) as well as Ni-based substrate (TLP mechanism) occurred to complete the transformation (Cu,Ti)l + Cs + Nis → TiCs + (Cu,Ni)s. Thereby, a joint with high-temperature resistance and excellent mechanical properties was obtained in relatively short holding time. The melting-point of the joint (1050 °C) was obviously higher than that of Cu-Ti alloy (898 °C) in the filler. The bonded joints exhibited shear strengths of 229, 225 and 104 MPa at room temperature, 600 °C and 1000 °C, respectively.

Microstructure and mechanical characterization of Si3N4/nickel-based superalloy joints with Ti/Au/Ni interlayers

The Si3N4 ceramic was joined to nickel-based superalloy via partial transient liquid phase bonding with Ti/Au/Ni interlayers. The interfacial microstructure and strength of joints were examined by methods of scanning electron microscopy, transmission electron microscopy, X-ray diffraction and a three-point flexural test. The results revealed the joint between Si3N4 and Ni interlayer consisted of TiN layer, Au-rich phase, Ni-rich phase and tiny TiO phase. The highest flexural strength of 211 MPa was achieved at room temperature, and the high-temperature strength of joints reached up to 117 MPa when testing at 1073 K. Post-bonding treatment indicated the joint strength of 120 MPa was obtained after annealing in air at 1073 K for 100 h, which exhibited superior oxidation resistant.

Effect of bonding temperature on microstructure and shear strength of the dissimilar Al/Al-27Si joints bonded by partial transient liquid phase bonding

The microstructure and shear strength of the Al alloy/Al-27Si alloy (Al/Al-27Si) joints with Cu interlayer bonded at different temperatures were investigated in the present study. Results show that a soldering seam with many eutectic phases is obtained in the Al/Al-27Si joints. These eutectic phases are mainly composed of θ-CuAl2 phase, α-Al phase and Si phase. With the increase of bonding temperature, the width of soldering seam and the average size of Si particles gradually increase, while the density of eutectic θ-CuAl2 phase deceases. The morphologies of Si phases transform from the granular particles into the needle-like shape when the temperature increases to 560 °C. The penetration of eutectic phases into the Al matrix along the grain boundaries is generated and the non-planar Al/soldering-seam interfaces are developed. With the increase of bonding temperature, the shear strengths of Al/Al-27Si joints firstly increase because of the better joining effect and less micro-cracks, and then decrease resulting from the morphology transformation of Si phases. The maximum shear strength of 70.4 MPa is achieved at 550 °C.

The preparation and mechanical properties of carbon/carbon (C/C) composite and carbon fiber reinforced silicon carbide (Cf/SiC) composite joint by partial transient liquid phase (PTLP) diffusion bonding process

Using Ti/Ni/Ti multiple foils as interlayer, carbon/carbon (C/C) composite was bonded to carbon fiber reinforced silicon carbide (Cf/SiC) composite by partial transient liquid phase (PTLP) diffusion bonding process. The multiple gradient structures, i.e. C/C composite | Ti-C reaction layer | Ni-Ti intermetallic compound | residual Ni foil | Ni-Ti intermetallic compound | Ti-C reaction layer | Cf/SiC composite, were formed during joining process. All the interfaces are bonded well, except for some micro-pores appeared in the interface between the residual Ni layer and Ni-Ti layer. The shear strength of the joint was 44.7 ± 12.8 MPa at room temperature. The X-ray result indicates that only diffraction peaks of C, TiCx and Ni-Ti Intermetallic compound were observed, while no diffraction peaks of Si were found on the fracture surface. Thus, it could be deduced that fracture occurred in the interfacial area adjacent to C/C composite side.

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 °C 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 σ 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 min, 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.

Microstructure and Properties of the Al-27Si/Cu/Al-50Si Joint Brazed by the Partial Transient Liquid Phase Bonding

Al-27Si and Al-50Si were brazed by using a thin Cu interlayer. The metallurgical bonding without obvious defects is achieved, and a wide brazing seam consisting of fine eutectic structures and coarse Si particles is formed in the Al-27Si/Cu/Al-50Si joint. The deposition of Si element in the liquid phases during solidification results in the formation of the larger Si particles and ultra-small Si particles in the brazing seam. The shear strength of the joint reaches 63 MPa.

Microstructural evolution and mechanical properties in the partial transient liquid phase diffusion bonding of tungsten to steel

The paper describes the design and examination of Ti/Cu double interlayer to produce a joint between tungsten and steel. Partial transient liquid phase diffusion bonding was performed by a double stage bonding process. To join tungsten to steel, the brazing of steel to a Cu interlayer (500 μm) was carried out at 1050 °C followed by transient liquid phase diffusion bonding to tungsten using an active Ti interlayer (25 μm) at 1000 °C. Microstructural evolution was studied at different bonding times (5, 15, 30, 60 and 180 min) to reveal the diffusion behavior of Ti atom in the interfacial zone between W and Cu. With the increase of the bonding time, the inserted active Ti interlayer and the formed Ti–Cu base intermetallic phases tend to be molten and consumed by the formed liquid alloy in the W-steel joint, while the tensile strength of the joint increases. The strength of the bonded specimens is as high as 412 MPa at the bonding time of 180 min. This technique provides a reliable method of bonding W to steel.

Influence of micro-oxidation on joints of C/C composites and GH3044 for large-size aerospace parts

To improve the bonding strength of carbon/carbon (C/C) composites and GH3044 nickel-based superalloy, the bonding interlayer with Ti/Ni/Cu/Ni multiple foils were prepared by a two-step technique involving micro-oxidation and partial transient liquid phase (PTLP) process. Interface characteristics and mechanical behavior of joints were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), laser scanning confocal microscope (LSCM) and energy X-ray dispersive spectrometer (EDS). Results show that a porous layer on C/C composites is formed by micro-oxidation for more than 2 min at 1073 K in air, which provides a diffusion path for liquid phase to infiltrate into C/C substrate and generate a wedge interlocking interface. After micro-oxidation for 4 min, the shear strength of joints reaches 32.09 ± 1.98 MPa what is 36.73% higher than that of joints without micro-oxidation (23.47 ± 1.15 MPa). The increase of shear strength remarkably depends on physical interlocking and chemical bonding at porous interface.

Interfacial microstructure of partial transient liquid phase bonding of Si3N4 to nickel-base superalloy using Ti/Au/Ni interlayers

The Si3N4 ceramic was joined to DZ483 superalloy by partial transient liquid phase bonding using Ti/Au/Ni/Ti multi-interlayers. The interfacial microstructure and crystallographic orientations between the Si3N4 ceramic and the Ni interlayer were analyzed by scanning and transmission electron microscope. The results indicated that the interfacial microstructure of the joint consists of three main phases: a TiN reaction phase, an Au-rich phase, and a lamellar Ni-rich phase distributed homogenously in the Au-rich phase. The nano-scale wavy interface was observed at the Si3N4/TiN interface, which was thought to provide high mechanical strength. A possible mechanism for the formation of interfacial structure observed was discussed.

Interfacial microstructure and high-temperature strength in silicon nitride/nickel-based superalloy bonding

Reliable Si3N4/nickel-based superalloy joints were obtained by partial transient liquid phase bonding with a Ni/Cu/Ti multi-interlayer. The flexural strengths of the joints were investigated at elevated temperatures. The maximum high-temperature bending strength of 115 MPa was achieved when the joint was tested at 1073 K. Microstructures and compositions of the joints after high-temperature testing were analyzed by scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy (TEM). A reaction layer with a thickness of about 3 μm was developed at the interface. The TEM results revealed a fine grain microstructure in the reaction layer of the joint after undergoing bending test at 1073 K. Cu-rich precipitates are observed in the fine-grained reaction layer by TEM. In addition, the high-temperature fracture mechanism of the joints was discussed. The fractures of the joints at room temperature exhibited a brittle fracture characteristic, while plastic deformation of the interlayers in the joint occurred at elevated temperatures.

Interfacial microstructure and mechanical characterization of silicon nitride/nickel-base superalloy joints by partial transient liquid phase bonding

Si3N4 ceramic has been joined successfully to nickel-based superalloy by partial transient liquid phase (PTLP) bonding using Ni/Cu/Ti multi-interlayers. The interfacial microstructure and strength of the joints were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a three-point bending test. According to the TEM analysis, it was found that a TiN reaction layer was formed at the Si3N4/filler alloy interface. The TiN reaction layer was composed of two zones: one next to the Si3N4 ceramic with a thickness of about 0.4μm and the other zone with grains of about 0.8μm. The microstructure of the joint between the Si3N4 and the Cu interlayer can be described as: TiN layer with fine grains/TiN layer with coarse grains/Ti2Ni layer. Ni3Ti and CuTi2 phases were produced at the interface between the Cu interlayer and the DZ483 superalloy. The room-temperature average strength of the joint was 147MPa, and 96MPa was achieved when the joints were tested at 1073K.

Effect of temperature on the microstructure and bonding strength of partial transient liquid phase bonded WC–Co/40Cr joints using Ti/Ni/Ti interlayers

Partial transient liquid phase bonding of WC–Co cemented carbide to 40Cr steel has been performed using a selected Ti/Ni/Ti multi-interlayer in vacuum in the temperature range of 950–1100°C. The interfacial microstructures of the joints revealed that the two original titanium layers were completely consumed and transformed into active transient liquid phase which would react with the two base materials. The transient liquid phase penetrated into the cemented carbide, leading to the formation of a transition layer consisting of reaction-formed TiC and dispersed WC particles. In contrast, an individual layer of TiC was identified at the steel side. Moreover, two Ni–Ti intermetallic compound (NiTi and Ni3Ti) layers were also observed on both sides of the residual nickel core layer. And the NiTi layer was gradually consumed due to the aggravation of interfacial reaction as the bonding temperature was increased, accompanying with the growth of the TiC layers and Ni3Ti layers. The shear strength of the joints increased firstly and then decreased sharply when the bonding temperature was higher than 1050°C, since the Ni3Ti layer was greatly thicken where most of the joint failures tended to occur. The maximum strength of 137MPa was obtained at the moderate temperature of 1000°C.

A new partial transient liquid-phase bonding process with powder-mixture interlayer for bonding Cf/SiC composite and Ti–6Al–4V alloy

A new partial transient liquid-phase (PTLP) process was carried out for bonding Cf/SiC composite and Ti–6Al–4V alloy at 980°C for 30min. Mixed powders of Ti54.8Ni34.4Nb10.8 (at%) eutectic and Nb metal were used as an interlayer, which will be a liquid phase coexisting with solid particles at the bonding temperature. Compared with typical multi-layer interlayer in PTLP bonding, the powder-mixture interlayer is more flexible in the design of joint structure and bonding surface, which needs less bonding time and benefits to release the thermal stress in the joint. The microstructure and formation mechanism of the bonded joints have been preliminarily investigated. The results showed that a reaction layer consisting of TiC and NbC formed at the Cf/SiC composite interface. A diffusion layer grew on the interface of TC4 alloy. In the connection layer, the residual Nb particles were wrapped by β-(Ti,Nb) phases and distributed in Ti2Ni matrix together with the other massive β-(Ti,Nb) phases. Due to good plasticity and dispersive distribution, the residual Nb particles would help to release the thermal stress in the joint.

Interfacial structure and strength on Ti(C,N) joint using liquid phase diffusion bonding with Ti/Ni interlayer

Partial transient liquid phase diffusion bonding (PTLP-DB) on Ti(C,N) cermet was studied in the present paper using Ti/Ni/Ti foil sandwich structure as the interlayer. The interfacial structure and element distribution at the interface were observed using SEM, electron probe microanalysis and X-ray diffraction. The joint strength was measured using four-point bending test. The results showed that metallurgical bonding between Ti(C,N) cermet was achieved using PTLP-DB. Near Ti(C,N) cermet side, a strong chemical reaction occurred to produce an interfacial multilayer containing Ti–Al and Ti–Ni intermetallics. Different bonding times during PTLP-DB were also studied, and there was an optimum time during bonding. With a shorter bonding time, voids were observed at the interface, while with a prolonged time, the bending strength on the joints also decreased due to the overgrowth on intermetallic layer and the existence of high gradient residual stress at the interface.

Effect of Bonding Temperature on the Microstructures and Strengths of C/C Composite/GH3044 Alloy Joints by Partial Transient Liquid-Phase (PTLP) Bonding with Multiple Interlayers

With the use of Ti/Ni/Cu/Ni multiple foils as interlayer, carbon/carbon (C/C) composite was bonded to Ni-based superalloy GH3044 by partial transient liquid-phase bonding technique. The effect of bonding temperature on the microstructures and strengths of the joints was investigated. The results showed that gradient structural multiple interlayers composed of “C–Ti reaction layer/Ti–Ni intermetallic compound layer/Ni–Cu sosoloid/residual Cu layer/Ni-GH3044 diffusion layer” were formed between C/C composite and GH3044. The shear strength of the C/C composite/GH3044 joint reached the highest value of 26.1 MPa when the bonding temperature was 1,030 °C. In addition, the fracture morphology showed that the fracture mode changed with the increase of bonding temperature.