Diffusion Brazing of Single Crystalline Nickel Base Superalloys Using Boron Free Nickel Base Braze Alloys

2008 ◽  
Vol 273-276 ◽  
pp. 294-299 ◽  
Author(s):  
Paul Heinz ◽  
Andreas Volek ◽  
Robert F. Singer ◽  
Markus Dinkel ◽  
Florian Pyczak ◽  
...  
Keyword(s):  
Melting Point ◽  
Liquid Phase ◽  
Gas Turbines ◽  
Transient Liquid Phase ◽  
Base Material ◽  
Transient Liquid Phase Bonding ◽  
Single Crystalline ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
Diffusion Behaviour

Brazing is a well established repair technique for high temperature components in both industrial gas turbines and aero engines. Conventional nickel base braze alloys contain boron or silicon as melting point depressing elements. The major benefit of boron and silicon compared to other melting point depressants is its large effect on the melting point and its high diffusion coefficient in nickel base superalloys. However these elements promote precipitation of undesired brittle phases during the brazing process. To avoid these phases, transient liquid phase bonding in combination with boron and silicon free brazing alloys will be examined in this work. The influence of the brazing temperature on solidification and diffusion behaviour during transient liquid phase bonding for a single crystalline first generation and a second generation superalloy will be reported. Our experiments show that isothermal solidification without precipitation of brittle phases in the braze joint or the base material can be achieved. The brazed joint consists of fine γ/γ´ microstructure. EBSD measurements demonstrated that the single crystalline orientation of the base material was maintained throughout the joint. Electron probe micro analysis is used to characterize the diffusion behaviour. Solidification velocity will be compared with the theory of transient liquid phase bonding established by Tuah-Poku [1].

Advancements in Fast Epitaxial High-Temperature Brazing of Single-Crystalline Nickel-Base Superalloys

2009 ◽  
Author(s):  
Britta Laux ◽  
Sebastian Piegert ◽  
Joachim Ro¨sler
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Base Material ◽  
Secondary Phases ◽  
Single Crystalline ◽  
Thermodynamic Simulations ◽  
Nickel Base Superalloys ◽  
Stray Grains ◽  
Nickel Base ◽  
Nickel Manganese

High temperature diffusion brazing is a very important technology for filling cracks in components from single-crystalline nickel-base superalloys as used in aircraft engines and stationary gas turbines: alloys, which are similar to the base material, are enhanced by a fast diffusing melting-point depressant (MPD) like boron or silicon, which causes solidification by diffusing into the base material. Generally, epitaxial solidification of single-crystalline materials can be achieved by use of conventional braze alloys, however, very long hold times are necessary to provide a complete diffusion of the MPD out of the braze gap. If the temperature is lowered before diffusion is completed, brittle secondary phases precipitate, which serve as nucleation sites for stray grains and, therefore, lead to deteriorating mechanical properties. It was demonstrated in earlier works that nickel-manganese-based braze alloys are appropriate systems for the braze repair of particularly wide gaps in the range of more than 200 μm, which allow a significant shortening of the required hold times. This is caused by the complete solubility of manganese in nickel: epitaxial solidification can be controlled by cooling in addition to diffusion. In this work, it will be shown that the nickel-manganese-based systems can be enhanced by chromium and aluminium, which is with regard to high-temperature applications a very important aspect. Furthermore, it will be demonstrated that silicon, which could be identified as appropriate secondary MPD in recent works, can be replaced by titanium, as this element has additionally a γ′ stabilizing effect. Several braze alloys containing nickel, manganese, chromium, aluminium and titanium will be presented. Previously, the influence of the above mentioned elements on the nickel-manganese-based systems will be visualized by thermodynamic simulations. Afterwards, different compositions in combination with a heat treatment, which is typical for nickel-base superalloys, will be discussed: a microstructure, which is very similar to that within the base material can be presented.

scholarly journals Transient Liquid Phase Bonding of Pairings of Parent Superalloy Material with Different Composition and Grain Structure

2011 ◽  
Vol 278 ◽  
pp. 454-459 ◽  
Author(s):  
Susanne Steuer ◽  
Sebastian Piegert ◽  
M. Frommherz ◽  
Robert F. Singer ◽  
Alfred Scholz
Keyword(s):  
Liquid Phase ◽  
Elevated Temperatures ◽  
Turbine Blades ◽  
Transient Liquid Phase ◽  
Grain Structure ◽  
Transient Liquid Phase Bonding ◽  
Nickel Base Superalloys ◽  
High Temperature Components ◽  
Nickel Base ◽  
Term Creep

Joining of different nickel-base superalloys could simplify the manufacturing of turbine blades. The used technique of choice is transient liquid phase bonding, which is an established repair technology for high temperature components. Two nickel-base superalloys with distinct composition and grain structure are bonded and the joints are analysed regarding the microstructure. To quantify the mechanical properties of these joints, tensile and short term creep rupture tests were performed at room and elevated temperatures.

Advanced Braze Alloys for Fast Epitaxial High-Temperature Brazing of Single-Crystalline Nickel-Base Superalloys

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Britta Laux ◽  
Sebastian Piegert ◽  
Joachim Rösler
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Base Material ◽  
Secondary Phases ◽  
Single Crystalline ◽  
Thermodynamic Simulations ◽  
Nickel Base Superalloys ◽  
Stray Grains ◽  
Nickel Base ◽  
Nickel Manganese

High-temperature diffusion brazing is a very important technology for filling cracks in components from single-crystalline nickel-base superalloys as used in aircraft engines and stationary gas turbines: Alloys, which are similar to the base material, are enhanced by a fast diffusing melting-point depressant (MPD) like boron or silicon, which causes solidification by diffusing into the base material. Generally, epitaxial solidification of single-crystalline materials can be achieved by use of conventional braze alloys; however, very long hold times are necessary to provide a complete diffusion of the MPD out of the braze gap. If the temperature is lowered before diffusion is completed, brittle secondary phases precipitate, which serve as nucleation sites for stray grains and, therefore, lead to deteriorating mechanical properties. It was demonstrated in earlier works that nickel-manganese-based braze alloys are appropriate systems for the braze repair of particularly wide gaps in the range of more than 200 μm, which allow a significant shortening of the required hold times. This is caused by the complete solubility of manganese in nickel: Epitaxial solidification can be controlled by cooling in addition to diffusion. In this work, it will be shown that the nickel-manganese-based systems can be enhanced by chromium and aluminum, which is with regard to high-temperature applications, a very important aspect. Furthermore, it will be demonstrated that silicon, which could be identified as appropriate secondary MPD in recent works, can be replaced by titanium as this element has additionally a γ′ stabilizing effect. Several braze alloys containing nickel, manganese, chromium, aluminum, and titanium will be presented. Previously, the influence of the above mentioned elements on the nickel-manganese-based systems will be visualized by thermodynamic simulations. Afterward, different compositions in combination with a heat treatment, which is typical for nickel-base superalloys, will be discussed: A microstructure, which is very similar to that within the base material, can be presented.

Mathematical Modeling and Experimental Investigations of Isothermal Solidification during Transient Liquid Phase Bonding of Nickel Superalloys

2006 ◽  
Vol 15-17 ◽  
pp. 882-887 ◽  
Author(s):  
Muhammad A. Arafin ◽  
Mamoun Medraj ◽  
Daniel P. Turner ◽  
Philippe Bocher
Keyword(s):  
Liquid Phase ◽  
Transient Liquid Phase ◽  
Isothermal Solidification ◽  
Holding Time ◽  
Inconel 625 ◽  
Experimental Investigations ◽  
Transient Liquid Phase Bonding ◽  
Holding Period ◽  
Nickel Base ◽  
Time Required

Mathematical model, based on Fick’s second law of diffusion, was used to predict the time required to complete isothermal solidification and to determine the effect of process variables during the transient liquid phase bonding of Inconel 625 and 718 superalloys with nickel based brazing filler alloy BNi-2. Experimental investigations were carried out in the range of 1325 – 1394K to verify the model and the predicted times were in excellent agreement with the experimentally determined values. The obtained activation energies for diffusion of boron were very close to the ones reported for other nickel base polycrystalline superalloys; however, it was observed that the time required for complete isothermal solidification are significantly less than that of other nickel based superalloys with different nickel based brazing filler alloys. Because of this advantage, these combinations of base and filler alloys are expected to replace other currently used ones. Further, significant reduction of holding time was observed with increasing brazing temperature and with decreasing joint gap. The composition of the joints at the end of holding period, when the holding time was not sufficient to complete isothermal soldification, has been determined in order to predict the amount of brittle eutectic phases in the final joint microstructures.

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