Nickel Base Superalloys Single Crystal Growth Technology for Large Size Buckets in Heavy Duty Gas Turbines

A larger size bucket with superior high temperature strength is required for future land based gas turbines. From the viewpoint of high temperature mechanical properties, single crystal alloys are rather promising. To grow larger sized single crystals of nickel base superalloys, a two stage heating and bypass process in which single crystal growth paths are incorporated into large cross sectional positions such as platforms has been developed. It results in successful single crystal growth of alloys for buckets with a total length of 170mm and large lateral cross section. Characteristics of single crystal buckets made by the bypass process and properties of an alumina mold prepared for a single crystal casting are described herein.

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High Temperature Mechanical Properties of CMSX4+Yttrium Single-Crystal Nickel-Base Superalloys SRR 99 and CMX-4

Superalloys 1992 (Seventh International Symposium) ◽

10.7449/1992/superalloys_1992_775_784 ◽

1992 ◽

Cited By ~ 2

Author(s):

M. Marchionni ◽

D. Goldschmidt ◽

M. Maldini

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Single Crystal ◽

High Temperature Mechanical Properties ◽

Nickel Base Superalloys ◽

Nickel Base

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Hydrodynamics and oscillation of temperature in single crystal growth from high-temperature solutions with use of ACRT

Journal of Crystal Growth ◽

10.1016/0022-0248(92)90682-9 ◽

1992 ◽

Vol 119 (3-4) ◽

pp. 297-302 ◽

Cited By ~ 7

Author(s):

V.M. Masalov ◽

G.A. Emel'chenko ◽

A.B. Mikhajlov

Keyword(s):

Crystal Growth ◽

High Temperature ◽

Single Crystal ◽

Single Crystal Growth

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

Volume 4: Cycle Innovations; Industrial and Cogeneration; Manufacturing Materials and Metallurgy; Marine ◽

10.1115/gt2009-59264 ◽

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.

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