Complete Isothermal Solidification Research Articles

Transient Liquid Phase Bonding of Nitrogen Containing Duplex Stainless Steel UNS S31803 Using Ni-Cr-Fe-Si-B Insert Metal

Microstructural evolution during transient liquid phase (TLP) bonding of nitrogen containing duplex stainless steel UNS S31803 has been investigated. In order to evaluate mechanical property of joint, tensile strength test was carried out at room temperature. TLP bonding was conducted at the temperature range 1283–1353 K for 0–1000 s under a vacuum of 6.7 mPa using Ni–7 mass%Cr–3 mass%Fe–4.5 mass%Si–3.2 mass%B amorphous insert metal. The results show that the volume fraction of austenite (γ) decreased with increasing bonding temperature and holding time. Particularly, in the case of prolonged holding time, the depleted area of γ phase was observed in the base metal adjacent to joints. There were linear correlations between the width of the remaining liquid phase and square root of holding time at each bonding temperature. In this investigation, the secondary phases formed in the joint area were (Cr, Mo) borides dominantly. For the specimen bonded for longer time up to 1000 s, boron nitride formed at the center and interface of joint area, on the other hand, the amount of borides decreased compared with the case of shorter bonding time. Tensile strength increased with holding time, and the bonding efficiency was ∼94% for the specimen held for 1000 s at 1353 K. Tensile strength of joint depended on, for a short holding time, brittle eutectic and borides, and after completion of isothermal solidification, depended on the boron nitride formed at the joint interface.

Joining of NiAl to Nickel-Base Alloys by Transient Liquid Phase Bonding

ABSTRACTA transmission and scanning electron microscope investigation is undertaken to study microstructural development during transient liquid phase (TLP) bonding of NiA1 to Ni-base substrates. The bonds were produced through a conventional technique employing a Cu foil interlayer or a widegap technique using a composite preform containing powders of NiAl and Cu. The time required for completion of isothermal solidification was greatly reduced in wide-gap bonds as compared to conventional bonds. Microstructural features of conventional TLP bonds of polycrystalline-NiAl/Ni were controlled by the ratio of Al: Cu across the joint. The precipitation of the a phase encountered in polycrystalline- NiAl/Martin Marietta 247 superalloy (MM247) bonds was suppressed in wide-gap bonds of single crystal-NiAl(Hf) and MM247. In general, the extent of second phase precipitation, in the asbonded condition, was greatly reduced by the use of the wide-gap technique. However, extensive precipitation of HfC and W-rich phases was observed after post-bond heat treatments.

Phase Transformations during Transient Liquid Phase Bonding of NiAl

Abstract: Transient liquid phase (TLP) bonding is a joining process in which a liquid-forming interlayer is placed between the substrates to be joined. At the bonding temperature, the interlayer initially liquates. Subsequently, interdiffusion between the liquid interlayer and the adjacent substrates results in a change in the overall composition of the joint, such that isothermal resolidification of the joint takes place. Standard models of the TLP process assume the sequential occurrence of discrete dissolution, isothermal solidification, and homogenization processes. This study uses edge-on transmission electron microscopy investigations to challenge the general applicability of such standard models to the TLP bonding of a variety of systems involving the B2 type intermetallic compound NiAl as a substrate material. This article considers the formation of boride phases apparently at the bonding temperature in NiAl/Ni-Si-B/Ni bonds. The precipitation of repeating sequences of phases in NiAl/Cu/Ni joints and the reliquation of the NiTi substrate in NiAl/Cu/NiTi bonds after the completion of isothermal solidification are examined.

Influence of isothermal solidification on microstructural development in Ni–Si–B filler metals

Abstract An examination is reported of the microstructure of joints between nickel substrates fabricated using Ni–Si–B filler metal (AWS classification BNi-3). This investigation was undertaken because the presence of residual boride and silicide phases after joining can affect the subsequent mechanical properties of the joint. The microstructures developed in the joints are compared with those formed in similarly heat treated filler metal. Various models of the transient liquid phase process are also considered and predicted times to complete isothermal solidification are compared with experimental values. An initial examination of the influence on filler metal microstructure of a ternary addition (chromium) to the substrate is included.MST/1506

Ｎｉ基超耐熱合金の液相インサート金属拡散接合に関する研究（第６報） 合金粉末を用いた液相インサート金属拡散接合法の開発

This study developed the new Transient Liquid Insert Metal Diffusion Bonding (TLIM-bonding) technique using alloying powder whose chemical compositions were similar to those of base metal. The base metals used were commercial Ni-base superalloys such as MM007, MarM247 and Inconel 713C alloys. They were bonded with both a Ni-15%Cr-4%B amorphous insert metal and IN100 alloying powder sheet with the thickness of about 250 μm.In the case of a MM007 alloy, the times required for completion of isothermal solidification and sequent homogenizing process were about 0.6 ks and 86.4 ks at 1423 K, respectively using this technique even with the bonding clearance of about 100 μm. The former time was about 1/80 and the latter time was about 1/30 compare to the times obtained by a conventional TLIM bonding. The short period during homogenizing process may be due to element diffusion from alloying powder to base metal by three-dimensional diffusion process.The tensile strength of MM007, MarM247 and Inconel 713C joints at 1255 K were almost equal to those of each base metal, respectively.From the experimental results, it should be useful to insert alloying powder to a wide bonding clearance joint during TLIM-bonding in fabrication