Browse Prior Art Database

APPLICATION OF A NICKEL-BASED SUPERALLOY POWDER TO TURBINE VANE AIRFOIL SURFACES TO REDUCE HPT NOZZLE THROAT AREA

IP.com Disclosure Number: IPCOM000239426D
Publication Date: 2014-Nov-05
Document File: 5 page(s) / 75K

Publishing Venue

The IP.com Prior Art Database

Abstract

The present disclosure is related to an improved repair process for high pressure turbine nozzle airfoils.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 01 of 5

APPLICATION OF A NICKEL-BASED SUPERALLOY POWDER TO TURBINE VANE AIRFOIL SURFACES TO REDUCE HPT NOZZLE THROAT AREA

TECHNICAL FIELD

    The present disclosure is related to an improved repair process for high pressure turbine nozzle airfoils.

BACKGROUND

    High pressure turbine (HPT) nozzles are used in turbojet and turbofan engines between the combustor and the turbine. They include thin airfoils which are exposed to high pressure and temperature and therefore need to be maintained regularly and often need to be repaired or replaced due to erosion. The HPT nozzles are generally made of superalloys, which are then coated for protection against heat and oxidation. Environmental coatings and thermal barrier coatings in wide use include alloys, such as MCrAIX overlay coatings (where M is iron, cobalt and/or nickel, and X is yttrium or a rare earth element), and diffusion coatings that contain aluminum intermetallics, predominantly beta-phase nickel aluminide and platinum-modified nickel aluminides (PtAl). MCrAIX-type overlay coatings may be overcoated with an aluminide diffusion coating to further promote oxidation resistance.

    When HPT nozzles come into overhaul stations or repair stations for repair, typically the environmental diffusion coating is stripped by a chemical procedure. This chemical procedure removes not only the additive layer of the coating above the base metal, but also removes the diffusion layer (which is a combination of base metal and diffused coating). This loss of base metal thickness can be approximately 0.003" per surface. Also, additional processing of the part during repair procedures (e.g., vibro-tumble and grit blast) can remove additional parent


Page 02 of 5

material. This loss of parent material opens HPT nozzle throat area, and may result in the throat area exceeding allowable limits. Currently, dealing with having too great of a throat area involves scraping the part completely, using split vane repair, or using airfoil replacement repair. However, these methods are all relatively costly procedures, and are avoided if possible.

    As such, a new repair method is needed for certain engines that is time and cost efficient and can leave a balanced, tapered finish and meet throat area requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an HPT nozzle segment showing repaired airfoils with a tapered coating.

DETAILED DESCRIPTION

    A method is generally provided for repairing airfoils that leaves an even, tapered finish and meets throat area requirements designed to lower repair costs and lower the number of scrapped HPT nozzles. In particular, the present disclosure is directed to ensuring that the throat area between adjacent airfoils in a nozzle remains a proper size after repair.

    The throat area can be reduced by applying a nickel based M-Cr-Al-Y sup...