Turbine Blade for Industrial Gas Turbine and Industrial Gas Turbine

Abstract

A turbine blade for industrial gas turbine is used which includes a blade substrate formed of a single-crystal heat-resistant alloy containing C: 0.06 to 0.08%, B: 0.016 to 0.035%, Hf: 0.2 to 0.3%, Cr: 6.9 to 7.3%, Mo: 0.7 to 1.0%, W: 7.0 to 9.0%, Re: 1.2 to 1.6%, Ta: 8.5 to 9.5%, Nb: 0.6 to 1.0%, Al: 4.9 to 5.2%, Co: 0.8 to 1.2%, and the remainder substantially consisting of Ni with reference to mass, and includes a diffusion barrier layer, a metal layer, a bond coat, and a top coat, these layers and coats being stacked in this order on a surface of the blade substrate, the metal layer having a thickness of 5 to 30 μm. Thus, the turbine blade can be provided which has a thermal barrier coating formed without loss of a function of the diffusion barrier layer.

Description

CLAIM OF PRIORITY[0001]The present application claims priority from Japanese Patent application serial No. 2012-122810, filed on May 30, 2012, the content of which is hereby incorporated by reference into this application.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a long-life turbine blade for industrial gas turbine including a blade substrate of a low-Re (low-rhenium) single crystal alloy, the blade substrate having a thermal barrier coating (TBC) thereon, and an industrial gas turbine including the turbine blade.[0004]2. Description of Related Art[0005]Recently, combustion gas temperature of a gas turbine has been increased to improve efficiency. Along with this, each of alloy members such as a turbine blade and a turbine nozzle has had the thermal barrier coating (TBC).[0006]The TBC includes a top coat as a thermal barrier formed of an oxide having a low coefficient of thermal conductivity. Such an oxide typically includes ytt...

AI Technical Summary

Benefits of technology

This patent describes a new heat-resistant alloy that is used in high-temperature settings. The alloy has a special layer that prevents the diffusion of elements between the substrate and the bond coat, which could compromise the mechanical properties of the substrate. This layer, called a diffusion barrier layer, is effective in preventing the formation of a secondary reaction zone (SRZ) that can occur during exposure to high temperatures. In comparison, a test piece without this layer showed significant degradation in strength after exposure to 1,100°C for 600 hours. Overall, this new alloy has improved performance at high temperatures and is useful in a variety of applications.

Problems solved by technology

Thus, Al may diffuse from the bond coat to the substrate during high temperature service, causing formation of a secondary reaction zone (SRZ) in the substrate which may reduce strength of the substrate.

The alloy layer containing Ru or Re described in Patent Document 1, however, is increasingly decomposed at high temperature through a reaction of the substrate and the bond coat, and is thus failed to maintain the above-described effects.

In addition, the gas turbine blade has a unique issue, i.e. , has differences from an aircraft turbine blade that often includes a single crystal blade, as described below.

Hence, for example, while Patent Document 2 exemplifies formation of the barrier layer at high temperature (solution heat treatment temperature), such a process cannot be applied to the single-crystal gas turbine blade due to a possibility of recrystallization at a blade forming portion.

In such a case, however, the barrier layer has turned out to be somewhat brittle as a result of investigations of the inventors.

A large blade further has a significant issue, i.e., yield in a precision casting process of the blade.

Third, such a difference in blade size is also associated with a deposition process of TBC.

A physical evaporation process which allows a large number of blades to be processed in one batch is costly promising for the small aircraft turbine blade.

The barrier layer deposited at low temperature is slightly brittle, and thus may be damaged to lose its functions by the blast treatment in the thermal spray process required for TBC operation of the large blade.

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