Evolution of the Diffusion Layer in a CMSX4 Single Crystal Superalloy

Aluminising processes are well-known techniques industrially adopted to enrich of aluminium the surface layers of Ni-based alloys thus improving their resistance to environmental interaction at high-temperature. The results of aluminising processes are typically described in terms of the presence, compositions and thickness of the sequence of layers at the surface of the treated parts. Following this approach, the microstructural features of the diffusion layers obtained under different holding times via vapour-phase type high-temperature low-activity process were experimentally investigated on single crystal CMSX4 alloy. The attention was particularly focused on the effect of the crystallographic orientation of the crystal on the coating features. The evolution of the diffusion layers under different process conditions was then taken into account.

Download Full-text

High-temperature oxidation kinetics of NiAl single crystal and oxide spallation as a function of crystallographic orientation

Materials Science and Engineering A ◽

10.1016/j.msea.2004.04.009 ◽

2004 ◽

Vol 381 (1-2) ◽

pp. 237-248 ◽

Cited By ~ 7

Author(s):

D Poquillon ◽

D Oquab ◽

B Viguier ◽

F Sénocq ◽

D Monceau

Keyword(s):

High Temperature ◽

Single Crystal ◽

Crystallographic Orientation ◽

Oxidation Kinetics ◽

High Temperature Oxidation ◽

Temperature Oxidation ◽

Oxide Spallation ◽

Kinetics Of

Download Full-text

Derivation of Temperature-Estimation Equation Based on Microstructural Changes in Coatings of In-Service Blades of Gas Turbines

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Education; Electric Power; Manufacturing Materials and Metallurgy ◽

10.1115/gt2010-22400 ◽

2010 ◽

Author(s):

Mitsutoshi Okada ◽

Tohru Hisamatsu ◽

Terutaka Fujioka

Keyword(s):

High Temperature ◽

Diffusion Layer ◽

Gas Turbines ◽

Aluminum Content ◽

Oxide Formation ◽

Diffusion Layer Thickness ◽

Temperature Estimation ◽

Diffusion Layers ◽

Barrier Coating ◽

Trailing Edges

A CoNiCrAlY-coated blade of an in-service gas turbine is analyzed, and a diffusion layer is formed along the boundary between the coating and the substrate due to the interdiffusion in the middle and tip of the blade. Such a layer is not observed in the vicinity of the blade root because of a comparatively low temperature during the operation. Coated specimens are prepared from the portions of the blade devoid of the diffusion layers, and the specimens are exposed to a high temperature in air. On the basis of the increase in the diffusion layer thickness, an equation for estimating the temperature of the blade is derived. Analysis of another in-service blade with a thermal barrier coating (TBC) is carried out. The aluminum-content decreases below the bond coat surface due to Al diffusion caused by the Al-oxide formation. This results in the formation of an Al-decreased layer (ADL) along the leading and trailing edges. The ADL is not observed at the center of the blade chord. The specimens are extracted from the portions of the blade that are devoid of ADL, and they are subjected to a high temperature in air. On the basis of the increase in the ADL thickness, a temperature-estimation equation is derived.

Download Full-text

Modelling of Phase Evolution during Aluminizing Processes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.278.228 ◽

2011 ◽

Vol 278 ◽

pp. 228-233 ◽

Cited By ~ 1

Author(s):

Elisabetta Gariboldi ◽

Marco Verani ◽

Christian Riva

Keyword(s):

Numerical Algorithm ◽

Research Work ◽

Phase Evolution ◽

Process Conditions ◽

Surface Layers ◽

Diffusion Layers ◽

Commercially Pure ◽

Environmental Interactions ◽

Convergence Problems ◽

User Friendly

Aluminizing processes are a well-known set of techniques industrially adopted to enrich in aluminum the surface layers of Ni-based alloys, thus improving their resistance to environmental interactions at high temperature. The results of aluminizing are described in terms of the presence, compositions and thickness of the sequence of the resulting surface diffusion layers. A combination of difficulties arising both from the mathematical and the material side restricted the number of available user-friendly models and their applicability to specific alloys or process conditions. The aim of the research work here presented is to overcome part of these difficulties. A synthesis of some well-established models was implemented in a robust numerical algorithm, that automatically prevents instabilities and convergence problems. Such numerical algorithm has been experimentally validated by comparing the results to the experimentally measured composition of profiles obtained for a set of vapor-phase aluminized samples of commercially pure Ni. The model was then applied to predict the effects of the process temperature and of the chemical composition of the surface.

Download Full-text

Derivation of Temperature-Estimation Equation Based on Microstructural Changes in Coatings of In-Service Blades of Gas Turbines

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4001998 ◽

2010 ◽

Vol 133 (2) ◽

Author(s):

Mitsutoshi Okada ◽

Tohru Hisamatsu ◽

Terutaka Fujioka

Keyword(s):

High Temperature ◽

Diffusion Layer ◽

Gas Turbines ◽

Aluminum Content ◽

Oxide Formation ◽

Diffusion Layer Thickness ◽

Temperature Estimation ◽

Diffusion Layers ◽

Barrier Coating ◽

Trailing Edges

A CoNiCrAlY-coated blade of an in-service gas turbine is analyzed, and a diffusion layer is formed along the boundary between the coating and the substrate due to the interdiffusion in the middle and tip of the blade. Such a layer is not observed in the vicinity of the blade root because of a comparatively low temperature during the operation. Coated specimens are prepared from the portions of the blade devoid of the diffusion layers, and the specimens are exposed to a high temperature in air. On the basis of the increase in the diffusion layer thickness, an equation for estimating the temperature of the blade is derived. An analysis of another in-service blade with a thermal barrier coating is carried out. The aluminum content decreases below the bond coat surface due to Al diffusion caused by the Al-oxide formation. This results in the formation of an Al-decreased layer (ADL) along the leading and trailing edges. The ADL is not observed at the center of the blade chord. The specimens are extracted from the portions of the blade that are devoid of ADL, and they are subjected to a high temperature in air. On the basis of the increase in the ADL thickness, a temperature-estimation equation is derived.

Download Full-text