WO1996005331A1 - Process for reconditioning steel surfaces - Google Patents

Process for reconditioning steel surfaces Download PDF

Info

Publication number
WO1996005331A1
WO1996005331A1 PCT/FI1995/000421 FI9500421W WO9605331A1 WO 1996005331 A1 WO1996005331 A1 WO 1996005331A1 FI 9500421 W FI9500421 W FI 9500421W WO 9605331 A1 WO9605331 A1 WO 9605331A1
Authority
WO
WIPO (PCT)
Prior art keywords
coating
reconditioning
weight
coating material
chromium
Prior art date
Application number
PCT/FI1995/000421
Other languages
French (fr)
Inventor
Jaakko Tenkula
Original Assignee
Telatek Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telatek Oy filed Critical Telatek Oy
Publication of WO1996005331A1 publication Critical patent/WO1996005331A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/18—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C23C4/08—Metallic material containing only metal elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/005—Repairing methods or devices

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Coating By Spraying Or Casting (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

The invention relates to a method for the reconditioning and coating of bearing and sealing surfaces of a steam turbine rotor and of other steal parts which in a turbine are exposed to corrosive and/or erosive wear caused by hot, moist steam or to mechanical damage, in such a manner that the surface to be reconditioned and coated is sprayed thermally with a coating material alloyed with a large amount of nickel and chromium, which, after the coating process, is machined to the desired shape, dimension and surface quality.

Description

Process for reconditioning steel surfaces
The invention relates to a method for the reconditioning of rotor axle labyrinth sealings and bearing surfaces in a steam turbine so as to restore the said surfaces to their original dimensions.
As stated in FI patent applications 762881 and 771073, steel surfaces exposed to hot, moist steam at high pressure and velocity are subject to strong erosive and corrosive wear.
The labyrinth sealing grooves in a steam turbine rotor may in certain cases wear out entirely. The depth of the groove is usually 3-5 mm. In certain cases the bottom of the groove also becomes worn, and therefore 4-7 mm of new material must be introduced onto the surface in the reconditioning of the seal¬ ing groove, if restoring of the original dimensions is desired.
In general, thick coating layers are not necessary for the bearing surfaces of a turbine rotor in connection with recon¬ ditioning. However, in cases of severe damage, grooves several millimeters deep may form in the bearing surfaces, and thus thick coating layers may be necessary also for their recon¬ ditioning.
Damage due to the wear of a steam turbine rotor labyrinth sealing has up to now been repaired in two ways:
1. New grooves are machined in the rotor axle. Thereby the axle diameter is reduced.
2. The blades and other parts are removed from the rotor. After this the sealing surfaces are fill-welded and the axle is heat-treated, and thereafter the grooves are machined to the desired dimensions and the blades are reinstalled.
The reconditioning methods described above have the following drawbacks:
In each case the rotor must be transported from the power plant to the machine shop or the turbine manufacturer, and back, and this results in a long down time.
If the reconditioning is carried out by machining new grooves, the axle diameter is reduced, and after a few machinings a new rotor must be acquired.
- When the diameter of the labyrinth sealing grooves of the rotor is reduced, it is necessary to acquire new sealings, also with smaller diameters, for the mating side. This further leads to an increase of the number of spare parts.
- If the rotor axle is fill-welded, it is necessary to carry out a large number of various time-consuming steps, such as dismantling of the blades, preliminary heating, welding and the related long heat treatments, reassembling, etc. This further increases the down time and production losses.
In seeking a new method for the reconditioning of the sealing and bearing surfaces of a rotor axle, the problem is to find a coating material and method by which coatings which fulfill the following requirements can be produced:
the thickness of the coating must be at minimum 10 mm
the coating must be capable of being applied at the power plant
the coating must be machinable by lathing the coating must be sufficiently strong and adhere well to the base material
the coating must be resistant to erosive and corrosive wear caused by moist steam
the coating must not cause corrosive problems between the different parts of the turbine or in the steam pipe system and the heat exchangers
the thermal expansion of the coating must be close to the thermal expansion of carbon steels.
The above requirements substantially limit the alternative coatings usable. It is known that thick coatings can be formed by spraying martensitic stainless steels or aluminum bronze or tin bronze.
Martensitic stainless steel is very difficult to machine, and therefore it is not usable for the present purpose. The thermal expansion of bronzes is so great that a thick coating may detach from the axle during the start-up of the turbine, and therefore they cannot be used.
Since there were no ready solutions, long development work had to be done in connection with the present invention to solve the problem.
The primary object of the present invention is to provide a method for the reconditioning of the labyrinth sealings and bearing surfaces of the rotor in a steam turbine in such a manner that there is obtained a reliable coating which is suitable for the operating conditions concerned and by means of which the dimensions of the sealing and bearing surfaces can be restored to their original dimensions, and that the coating and related machining can be carried out on site rapidly and economically. The main characteristics of the invention are stated in the accompanying claims.
According to one preferred embodiment of the reconditioning technique according to the invention, the surface to be recon¬ ditioned is first preliminarily machined, for example by using a rotary lathe on site. Thereafter, thermal spraying is carried out using a NiCr-alloyed coating material. Finally the coated area is lathed to the desired shape and dimension. The bearing surfaces can additionally be ground on site to the desired surface quality.
According to the invention, the coating material used is pref¬ erably a metal alloy containing nickel 20-60 % by weight and chromium 15-30 % by weight, in particular nickel 40-60 % by weight and chromium 15-20 % by weight. The balance of the coating material may be steel. The coating material may be in the form of wire or powder. Commercial materials may be used as coating materials in accordance with the invention.
Coating materials according to the invention enable a coating over 10 mm thick to be sprayed. This is an essential prerequi¬ site for the reconditioning work, as stated above.
According to the invention, preferably a single-layer coating having a pos -machining thickness of approx. 0.3-10 mm is formed.
Coatings according to the invention are characterized in that there are large amounts of chromium oxides within the coatings, and that on the surface of the coating there is formed a dense and strong oxide film, which prevents erosive and corrosive wear caused by moist steam.
The thermal expansion of the coatings according to the inven¬ tion is the same as that of carbon steels, and thus the start¬ ups and shut-downs of the turbine will not cause problems. According to the invention the coating can be prepared by using flame, arc, plasma, and/or supersonic spraying, primarily, however, arc, plasma and/or supersonic spraying, in order to achieve a good adhesion of the coating to the base material and in order that the coating should have sufficient intrinsic strength against loads parallel to the axle.
The advantages of the reconditioning technique according to the invention over previous ones are as follows:
1. The labyrinth sealings and bearing surfaces of a rotor can be reconditioned rapidly on site at a power plant. Thus the down time will be short and production losses will be small.
2. The coatings used in the reconditioning technique will lengthen the useful life of the labyrinth sealings and at the same time the useful life of the rotor, and will lengthen the maintenance interval caased by sealing surfaces.
3. The dimensions of the sealing grooves and bearing surfaces are restored to the original dimensions by the recondi¬ tioning technique. This reduces the number of spare parts required.

Claims

Claims
1. A method for the reconditioning and coating of bearing and sealing surfaces of a steam turbine rotor and of other parts which in a turbine are exposed to corrosive and/or erosive wear caused by hot, moist steam or to mechanical damage, characterized in that the surface to be reconditioned and coated is sprayed thermally with a coating material alloyed with a large amount of nickel and chromiumm, which, after the coating process, is machined to the desired shape, dimension, and surface quality.
2. A method according to Claim 1, characterized in that the coating material is a metal alloy which contains nickel 20- 60 % by weight and chromium 15-30 % by weight.
3. A method according to Claim 1 or 2, characterized in that the coating material is a metal alloy which contains nickel 40-60 % by weight and chromium 15-20 % by weight.
4. A method according to any of Claims 1-3, characterized in that a single-layer coating is formed which has a thickness of 0.3-10 mm.
5. A method according to any of Claims 1-4, characterized in that the thermal spraying is carried out by the arc, plasma or supersonic method.
PCT/FI1995/000421 1994-08-09 1995-08-09 Process for reconditioning steel surfaces WO1996005331A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI943685 1994-08-09
FI943685A FI96970C (en) 1994-08-09 1994-08-09 Method for rehabilitating steel surfaces

Publications (1)

Publication Number Publication Date
WO1996005331A1 true WO1996005331A1 (en) 1996-02-22

Family

ID=8541180

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1995/000421 WO1996005331A1 (en) 1994-08-09 1995-08-09 Process for reconditioning steel surfaces

Country Status (2)

Country Link
FI (1) FI96970C (en)
WO (1) WO1996005331A1 (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999047723A1 (en) * 1998-03-14 1999-09-23 Dana Corporation Forming a plain bearing lining
EP1013786A1 (en) * 1998-12-22 2000-06-28 GE Aviation Services Operation (Pte) Ltd. Method for repairing a superalloy turbine component
EP1123987A1 (en) * 2000-02-11 2001-08-16 General Electric Company Repairable diffusion aluminide coatings
WO2002020212A2 (en) * 2000-09-08 2002-03-14 Mtu Aero Engines Gmbh Rotational machining and quality assurance method
EP1798302A1 (en) * 2004-08-23 2007-06-20 Kabushiki Kaisha Toshiba Method and equipment for repairing rotor
EP2256226A1 (en) * 2004-08-23 2010-12-01 Kabushiki Kaisha Toshiba Rotor repair method and rotor repair apparatus
WO2013025384A1 (en) * 2011-08-17 2013-02-21 General Electric Company Rotor seal wire groove repair
WO2014115162A2 (en) * 2013-01-28 2014-07-31 Abhay Vishwas Ranade Labyrinth seal with replaceable inner liner/ring
US9003663B2 (en) 2012-08-22 2015-04-14 Caterpillar Inc. Remanufacturing of bearings using isotropic finishing and thin film coatings

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2418607B2 (en) * 1974-04-11 1978-06-08 Brown Boveri-Sulzer Turbomaschinen Ag, Zuerich (Schweiz) High temperature anti-corrosion layer
JPS5538969A (en) * 1978-09-14 1980-03-18 Toshiba Corp Corrosion resistant carbon steel
EP0031580A1 (en) * 1979-12-29 1981-07-08 Ebara Corporation Coating metal for preventing the crevice corrosion of austenitic stainless steel
WO1985000127A1 (en) * 1983-06-28 1985-01-17 Castolin S.A. Pulverulent spraying material based on nickel-chromium
EP0224724A1 (en) * 1985-11-05 1987-06-10 The Perkin-Elmer Corporation Amorphous alloy
EP0293695A1 (en) * 1987-06-01 1988-12-07 General Electric Company Alloy powder mixture for treating alloys
WO1992004480A1 (en) * 1990-09-04 1992-03-19 Tampella Telatek Oy A coating, and a coating method, for a steam turbine and adjoining steel surfaces

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2418607B2 (en) * 1974-04-11 1978-06-08 Brown Boveri-Sulzer Turbomaschinen Ag, Zuerich (Schweiz) High temperature anti-corrosion layer
JPS5538969A (en) * 1978-09-14 1980-03-18 Toshiba Corp Corrosion resistant carbon steel
EP0031580A1 (en) * 1979-12-29 1981-07-08 Ebara Corporation Coating metal for preventing the crevice corrosion of austenitic stainless steel
WO1985000127A1 (en) * 1983-06-28 1985-01-17 Castolin S.A. Pulverulent spraying material based on nickel-chromium
EP0224724A1 (en) * 1985-11-05 1987-06-10 The Perkin-Elmer Corporation Amorphous alloy
EP0293695A1 (en) * 1987-06-01 1988-12-07 General Electric Company Alloy powder mixture for treating alloys
WO1992004480A1 (en) * 1990-09-04 1992-03-19 Tampella Telatek Oy A coating, and a coating method, for a steam turbine and adjoining steel surfaces

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 4, No. 73, C-12; & JP,A,55 038 969 (TOKYO SHIBAURA DENKI K.K.), 18 March 1980. *

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999047723A1 (en) * 1998-03-14 1999-09-23 Dana Corporation Forming a plain bearing lining
EP1013786A1 (en) * 1998-12-22 2000-06-28 GE Aviation Services Operation (Pte) Ltd. Method for repairing a superalloy turbine component
US6228510B1 (en) 1998-12-22 2001-05-08 General Electric Company Coating and method for minimizing consumption of base material during high temperature service
EP1123987A1 (en) * 2000-02-11 2001-08-16 General Electric Company Repairable diffusion aluminide coatings
WO2002020212A2 (en) * 2000-09-08 2002-03-14 Mtu Aero Engines Gmbh Rotational machining and quality assurance method
WO2002020212A3 (en) * 2000-09-08 2002-09-12 Mtu Aero Engines Gmbh Rotational machining and quality assurance method
US6886435B2 (en) 2000-09-08 2005-05-03 Mtu Aero Engines Gmbh Turning and quality assurance process for thermally sprayed turbomachine linings
EP1798302A4 (en) * 2004-08-23 2009-12-02 Toshiba Kk Method and equipment for repairing rotor
EP1798302A1 (en) * 2004-08-23 2007-06-20 Kabushiki Kaisha Toshiba Method and equipment for repairing rotor
EP2256226A1 (en) * 2004-08-23 2010-12-01 Kabushiki Kaisha Toshiba Rotor repair method and rotor repair apparatus
WO2013025384A1 (en) * 2011-08-17 2013-02-21 General Electric Company Rotor seal wire groove repair
US8893381B2 (en) 2011-08-17 2014-11-25 General Electric Company Rotor seal wire groove repair
EP2753799B1 (en) 2011-08-17 2018-06-06 General Electric Company Nutreparatur einer rotordrahtdichtung
EP2753799B2 (en) † 2011-08-17 2024-01-10 General Electric Company Nutreparatur einer rotordrahtdichtung
US9003663B2 (en) 2012-08-22 2015-04-14 Caterpillar Inc. Remanufacturing of bearings using isotropic finishing and thin film coatings
WO2014115162A2 (en) * 2013-01-28 2014-07-31 Abhay Vishwas Ranade Labyrinth seal with replaceable inner liner/ring
WO2014115162A3 (en) * 2013-01-28 2014-12-04 Abhay Vishwas Ranade Labyrinth seal with replaceable inner liner/ring

Also Published As

Publication number Publication date
FI96970C (en) 1996-09-25
FI96970B (en) 1996-06-14
FI943685A0 (en) 1994-08-09
FI943685A (en) 1996-02-10

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