US3834833A - Blade construction for axial-flow turbo-machines and method of protecting turbo-machine blades against stress corrosion cracking - Google Patents

Blade construction for axial-flow turbo-machines and method of protecting turbo-machine blades against stress corrosion cracking Download PDF

Info

Publication number
US3834833A
US3834833A US00333156A US33315673A US3834833A US 3834833 A US3834833 A US 3834833A US 00333156 A US00333156 A US 00333156A US 33315673 A US33315673 A US 33315673A US 3834833 A US3834833 A US 3834833A
Authority
US
United States
Prior art keywords
blade
turbo
axial
stress corrosion
corrosion cracking
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US00333156A
Inventor
G Faber
C Maggi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BBC Brown Boveri AG Switzerland
BBC Brown Boveri France SA
Original Assignee
BBC Brown Boveri France SA
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 BBC Brown Boveri France SA filed Critical BBC Brown Boveri France SA
Application granted granted Critical
Publication of US3834833A publication Critical patent/US3834833A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • F01D5/12—Blades
    • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
    • F01D5/286—Particular treatment of blades, e.g. to increase durability or resistance against corrosion or erosion
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below

Definitions

  • the invention is directed to a procedure for protecting the hardened leading edge of blades or vanes (hereinafter blades) of axial-flow turbo-machines against stress corrosion cracking.
  • BACKGROUND INFORMATION It is general practice to harden the leading edges of blades of axial-flow turbo-machines for the purpose of minimizing erosion of the blades.
  • the desired hardness may be obtained by various heat treatments, for example by flame hardening or by means of induction heat by high frequency.
  • hardened steel is more susceptible to stress corrosion cracking sometimes referred to in the art as stress crack corrosion than is unhardened steel.
  • Stress corrosion is discussed in The Making, Shaping and Treating of Steel, United States Steel Corporation, 1964, page 933.
  • Hardened alloy steel for example stainless steel containing 12 percent of chromium, exhibits a particular great tendency towards stress corrosion cracking. This susceptibility is dependent on various factors, among others the composition and the heat treatment condition of the steel. Further, it is dependent on the contaminants, for example chlorides, which are present in the flowing working medium of the turbo-machine and also on the tensile stresses which act on the respectively endangered portion of the blade.
  • Another object of the invention is to achieve such protection by technological, as distinguished from constructive, measures.
  • the leading edge of such a blade is imparted with a permanent, compressive prestress in the direction of the longitudinal axis of the blade.
  • the blades may be imparted with the permanent compressive prestress in exceedingly simple manner.
  • hardening of steel is effected by heating to a temperature above 850C. and subsequent cooling or quenching. Due to the martensite formation in the steel, a volume increase takes place. If only a portion of a steel work piece is hardened in the indicated manner, as is the case in the hardening of the leading edge of a blade, then a compressive stress or prestress occurs in the hardened portion, provided the remainder of the work piece, which remains cold or unheated during'the hardening, has a sufficiently large'cross-sectional area in order to enable it to absorb the resulting tensile stresses without being plastically deformed, i.e. beyond the yield point.
  • the leading edge portion of the blade to be hardened is not permitted to have a cross-sectional area in excess of 20 percent of the total cross section of the blade and the thus remaining 80 percent are maintained in cold, unheated condition during the hardening, whereby the hardened portion is imparted with the desired permanent compressive prestress.
  • FIGURE of the drawing is a crosssectional view of a blade of an axial-flow turbomachine.
  • the cross-sectional area of the blade is formed by the portions 1 and 2, portion 1 being the cross-sectional area of the hardened zone, to wit, the area of the leading edge of the blade.
  • This hardened zone 1 extends not only adjacent the leading edge but also adjacent a portion of the suction side of the blade.
  • the area 2 occupies the remainder of the crosssectional area of the blade.
  • the crosssectional area 1 amounts to at the most, and preferably less than, 20 percent of the total cross-sectional area, to wit, the sum of the cross-sectional area 1 and 2.
  • the hardening of the area 1 may be: accomplished by any conventional tempering treatment as previously re ferred to.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

A steel blade for an axial-flow turbo-machine is disclosed which has a hardened leading edge portion. In accordance with the invention, the hardened edge portion is imparted with a permanent compressive prestress in the direction of the longitudinal axis of the blade. This protects the blade against stress corrosion cracking.

Description

United States Patent Faber et a1.
[ BLADE CONSTRUCTION FOR AXIAL-FLOW TURBO-MACHINES AND METHOD OF PROTECTING TURBO-MACHINE BLADES AGAINST STRESS CORROSION CRACKING Inventors: Guy Faber, Oberrohrdorf; Carlo Maggi, Baden, both of Switzerland Assignee: Brown, Boveri & Company Ltd.,
Baden, Switzerland Filed: Feb. 16, 1973 Appl. No.: 333,156
Foreign Application Priority Data Feb. 18, 1972 Switzerland 2373/72 US. Cl. 416/241, 416/224 Int. Cl. F0ld 5/28 Field of Search 416/224, 241
References Cited UNITED STATES PATENTS 5/1959 Pekarek 416/241 [45.] Sept. 10, 1974 3,148,954 9/1964 Haas 416/241 X FOREIGN PATENTS OR APPLICATIONS 195,050 7/1923 Great Britain 416/224 Primary Examiner-Everett A. Powell, Jr. Attorney, Agent, or Firm-Toren, McGeady and Stanger [57] ABSTRACT A steel blade for an axial-flow turbo-machine is disclosed which has a hardened leading edge portion. In accordance with the invention, the hardened edge portion is imparted with a permanent compressive prestress in the direction of the longitudinal axis of the blade. This protects the blade against stress corrosion cracking.
2 Claims, 1 Drawing Figure PATENTED SE? 1 M974 3. 884.833
BLADE CONSTRUCTION FOR AXIAL-FLOW TURBO-MACHINES AND METHOD OF PROTECTING TURBO-MACHINE BLADES AGAINST STRESS CORROSION CRACKING FIELD OF INVENTION The invention is directed to a procedure for protecting the hardened leading edge of blades or vanes (hereinafter blades) of axial-flow turbo-machines against stress corrosion cracking.
BACKGROUND INFORMATION It is general practice to harden the leading edges of blades of axial-flow turbo-machines for the purpose of minimizing erosion of the blades. The desired hardness may be obtained by various heat treatments, for example by flame hardening or by means of induction heat by high frequency.
It is well known, however, that hardened steel is more susceptible to stress corrosion cracking sometimes referred to in the art as stress crack corrosion than is unhardened steel. The phenomenon of stress corrosion is discussed in The Making, Shaping and Treating of Steel, United States Steel Corporation, 1964, page 933. Hardened alloy steel, for example stainless steel containing 12 percent of chromium, exhibits a particular great tendency towards stress corrosion cracking. This susceptibility is dependent on various factors, among others the composition and the heat treatment condition of the steel. Further, it is dependent on the contaminants, for example chlorides, which are present in the flowing working medium of the turbo-machine and also on the tensile stresses which act on the respectively endangered portion of the blade. Since a blade of the indicated kind, during operation of the machine, is subjected to tensile stresses due to the centrifugal forces, and sometimes also due to forces caused by the working medium, also a hardened edge of such blades is attacked by stress corrosion cracking.
It has previously been proposed to reduce the mechanical stresses on the blades by construction measures. This, however, results indisadvantages such as,
SUMMARY OF THE INVENTION It is the primary object of the present invention to provide a procedure by means of which the hardened leading edge of a blade of an axial-flow turbo-machine is largely protected against stress corrosion cracking.
Another object of the invention is to achieve such protection by technological, as distinguished from constructive, measures.
Generally it is an object of the present invention to improve the characteristics of the blades of axial-flow turbo-machines.
Briefly, and in accordance with the invention, the leading edge of such a blade, and while it is being hardened, is imparted with a permanent, compressive prestress in the direction of the longitudinal axis of the blade.
If a blade which has been imparted with such an initial compressive stress is, during operation, subjected to tensile stresses caused by centrifugal or other forces, that portion of the blade which exhibits the compressive prestress is then completely, or at least to a very large extent, relieved of the pressure. Any tensile forces which may still arise in this portion of the blade are so insignificant that they do not cause any substantial. in.- crease in the stress corrosion cracking.
The blades may be imparted with the permanent compressive prestress in exceedingly simple manner. Generally, hardening of steel is effected by heating to a temperature above 850C. and subsequent cooling or quenching. Due to the martensite formation in the steel, a volume increase takes place. If only a portion of a steel work piece is hardened in the indicated manner, as is the case in the hardening of the leading edge of a blade, then a compressive stress or prestress occurs in the hardened portion, provided the remainder of the work piece, which remains cold or unheated during'the hardening, has a sufficiently large'cross-sectional area in order to enable it to absorb the resulting tensile stresses without being plastically deformed, i.e. beyond the yield point.
In a blade having an oblong profile of which merely one end portion, such as the leading edge, is to be hardened, the conditions are particularly unfavorable. Extensive experiments have indicated that a permanent compressive prestress in the direction of the longitudinal axis of the blade, which prestress thus also remains in cold condition, is imparted with certainty only to the hardened portion if the cross-sectional area of this hardened blade portion occupies at the most 20 percent of the total blade cross section. The remaining percent of the cross-sectional area of the unhardened blade portion can then effectively absorb the corresponding tensile stresses without. deformation.
Accordingly, and pursuant to the invention, the leading edge portion of the blade to be hardened is not permitted to have a cross-sectional area in excess of 20 percent of the total cross section of the blade and the thus remaining 80 percent are maintained in cold, unheated condition during the hardening, whereby the hardened portion is imparted with the desired permanent compressive prestress.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.
The single FIGURE of the drawing is a crosssectional view of a blade of an axial-flow turbomachine.
It will be noted that the cross-sectional area of the blade is formed by the portions 1 and 2, portion 1 being the cross-sectional area of the hardened zone, to wit, the area of the leading edge of the blade. This hardened zone 1 extends not only adjacent the leading edge but also adjacent a portion of the suction side of the blade. The area 2 occupies the remainder of the crosssectional area of the blade. In accordance with the invention and in order to create during the hardening the desired permanent compressive prestress, the crosssectional area 1 amounts to at the most, and preferably less than, 20 percent of the total cross-sectional area, to wit, the sum of the cross-sectional area 1 and 2. The hardening of the area 1 may be: accomplished by any conventional tempering treatment as previously re ferred to.
blade is protected against stress corrosion cracking.
2. The improvement of claim 1, wherein the crosssectional area of said hardened edge portion amounts to at the most twenty percent of the total crosssectional area of the blade.

Claims (2)

1. In a steel blade of an axial-flow turbo-machine, wherein the blade has a hardened edge portion, the improvement which comprises that said edge portion exhibits a permanent compressive prestress in the direction of the longitudinal axis of the blade, whereby said blade is protected against stress corrosion cracking.
2. The improvement of claim 1, wherein the cross-sectional area of said hardened edge portion amounts to at the most twenty percent of the total cross-sectiOnal area of the blade.
US00333156A 1972-02-18 1973-02-16 Blade construction for axial-flow turbo-machines and method of protecting turbo-machine blades against stress corrosion cracking Expired - Lifetime US3834833A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH237372A CH564147A5 (en) 1972-02-18 1972-02-18

Publications (1)

Publication Number Publication Date
US3834833A true US3834833A (en) 1974-09-10

Family

ID=4232248

Family Applications (1)

Application Number Title Priority Date Filing Date
US00333156A Expired - Lifetime US3834833A (en) 1972-02-18 1973-02-16 Blade construction for axial-flow turbo-machines and method of protecting turbo-machine blades against stress corrosion cracking

Country Status (11)

Country Link
US (1) US3834833A (en)
AT (1) AT316963B (en)
BE (1) BE795520A (en)
CA (1) CA1009125A (en)
CH (1) CH564147A5 (en)
DE (1) DE2211830A1 (en)
FR (1) FR2172727A5 (en)
GB (1) GB1418136A (en)
HU (1) HU165495B (en)
NL (1) NL7302234A (en)
SE (1) SE400579B (en)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4385866A (en) * 1979-08-02 1983-05-31 Tokyo Shibaura Denki Kabushiki Kaisha Curved blade rotor for a turbo supercharger
US4778345A (en) * 1985-03-15 1988-10-18 Ngk Spark Plug Co., Ltd. Turbine rotor
US5120197A (en) * 1990-07-16 1992-06-09 General Electric Company Tip-shrouded blades and method of manufacture
US5348446A (en) * 1993-04-28 1994-09-20 General Electric Company Bimetallic turbine airfoil
US5620307A (en) * 1995-03-06 1997-04-15 General Electric Company Laser shock peened gas turbine engine blade tip
US5742028A (en) * 1996-07-24 1998-04-21 General Electric Company Preloaded laser shock peening
US6004102A (en) * 1995-12-09 1999-12-21 Abb Patent Gmbh Turbine blade for use in the wet steam region of penultimate and ultimate stages of turbines
US6155789A (en) * 1999-04-06 2000-12-05 General Electric Company Gas turbine engine airfoil damper and method for production
US6551064B1 (en) 1996-07-24 2003-04-22 General Electric Company Laser shock peened gas turbine engine intermetallic parts
US20070243071A1 (en) * 1995-03-06 2007-10-18 Mannava Seetha R Laser shock peened gas turbine engine compressor airfoil edges
US20130287580A1 (en) * 2012-04-27 2013-10-31 General Electric Company Stress corrosion cracking resistance in superalloys

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5591009A (en) * 1995-01-17 1997-01-07 General Electric Company Laser shock peened gas turbine engine fan blade edges
JPH11182204A (en) * 1997-12-15 1999-07-06 Toshiba Corp Moving blade for turbine

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB195050A (en) * 1922-03-18 1923-07-19 Bbc Brown Boveri & Cie Improvements in steam turbine blades, and in the method of manufacturing such blades
US2888244A (en) * 1956-05-24 1959-05-26 Thompson Ramo Wooldridge Inc Fluid directing member
US3148954A (en) * 1960-06-13 1964-09-15 Haas Irene Turbine blade construction
US3371908A (en) * 1965-11-02 1968-03-05 Tokyo Shibaura Electric Co Turbine blading components and process of producing the same
US3564689A (en) * 1967-05-26 1971-02-23 Boehler & Co Ag Geb Method of fabricating a turbine blade having a leading edge formed of weld metal
US3729345A (en) * 1967-06-11 1973-04-24 Mitsubishi Heavy Ind Ltd Method for making propellers of high-strength and high-toughness cast steel

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB195050A (en) * 1922-03-18 1923-07-19 Bbc Brown Boveri & Cie Improvements in steam turbine blades, and in the method of manufacturing such blades
US2888244A (en) * 1956-05-24 1959-05-26 Thompson Ramo Wooldridge Inc Fluid directing member
US3148954A (en) * 1960-06-13 1964-09-15 Haas Irene Turbine blade construction
US3371908A (en) * 1965-11-02 1968-03-05 Tokyo Shibaura Electric Co Turbine blading components and process of producing the same
US3564689A (en) * 1967-05-26 1971-02-23 Boehler & Co Ag Geb Method of fabricating a turbine blade having a leading edge formed of weld metal
US3729345A (en) * 1967-06-11 1973-04-24 Mitsubishi Heavy Ind Ltd Method for making propellers of high-strength and high-toughness cast steel

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4385866A (en) * 1979-08-02 1983-05-31 Tokyo Shibaura Denki Kabushiki Kaisha Curved blade rotor for a turbo supercharger
US4778345A (en) * 1985-03-15 1988-10-18 Ngk Spark Plug Co., Ltd. Turbine rotor
US5120197A (en) * 1990-07-16 1992-06-09 General Electric Company Tip-shrouded blades and method of manufacture
US5348446A (en) * 1993-04-28 1994-09-20 General Electric Company Bimetallic turbine airfoil
US5620307A (en) * 1995-03-06 1997-04-15 General Electric Company Laser shock peened gas turbine engine blade tip
US20070243071A1 (en) * 1995-03-06 2007-10-18 Mannava Seetha R Laser shock peened gas turbine engine compressor airfoil edges
US6004102A (en) * 1995-12-09 1999-12-21 Abb Patent Gmbh Turbine blade for use in the wet steam region of penultimate and ultimate stages of turbines
US5742028A (en) * 1996-07-24 1998-04-21 General Electric Company Preloaded laser shock peening
US6551064B1 (en) 1996-07-24 2003-04-22 General Electric Company Laser shock peened gas turbine engine intermetallic parts
US6155789A (en) * 1999-04-06 2000-12-05 General Electric Company Gas turbine engine airfoil damper and method for production
US20130287580A1 (en) * 2012-04-27 2013-10-31 General Electric Company Stress corrosion cracking resistance in superalloys

Also Published As

Publication number Publication date
HU165495B (en) 1974-09-28
BE795520A (en) 1973-06-18
CH564147A5 (en) 1975-07-15
SE400579B (en) 1978-04-03
AU5228873A (en) 1974-08-22
CA1009125A (en) 1977-04-26
FR2172727A5 (en) 1973-09-28
AT316963B (en) 1974-08-12
GB1418136A (en) 1975-12-17
DE2211830A1 (en) 1973-08-23
NL7302234A (en) 1973-08-21

Similar Documents

Publication Publication Date Title
US3834833A (en) Blade construction for axial-flow turbo-machines and method of protecting turbo-machine blades against stress corrosion cracking
US5351395A (en) Process for producing turbine bucket with water droplet erosion protection
US5531570A (en) Distortion control for laser shock peened gas turbine engine compressor blade edges
EP0379922B1 (en) Turbine blade repair
CA2011414C (en) Turbine blade repair
US20070243071A1 (en) Laser shock peened gas turbine engine compressor airfoil edges
US7229253B2 (en) Fatigue-resistant components and method therefor
US3564689A (en) Method of fabricating a turbine blade having a leading edge formed of weld metal
JP2896713B2 (en) How to repair turbine blades
US7204677B2 (en) Countering laser shock peening induced blade twist
US5795412A (en) Method of manufacturing and repairing a blade made of α-β titanium
US3820419A (en) Method of reducing stress concentration and cracking failures in carbide tipped saws
JP4713796B2 (en) High strength steam turbine rotor and method for manufacturing a rotor without increasing stress corrosion cracking
US2920007A (en) Elastic fluid blade with a finegrained surface
US20100061863A1 (en) airfoil and methods of laser shock peening of airfoil
JPH0610613A (en) Method of repairing turbine blade
JPH01202389A (en) Manufacture of steam turbine long blade
US6267558B1 (en) Dual intensity peening and aluminum-bronze wear coating surface enhancement
US1763256A (en) Turbine blade
JPH09264102A (en) Fan vane for gas turbine engine
KR20080110335A (en) Heat treatment method for productivity improvement of propeller shaft
JP2001107138A (en) Welded impeller having high fatigue strength
JPS58120764A (en) Moving vane of steam turbine with superior strength at high temperature and low creep crack propagating speed
JP2984163B2 (en) How to extend the life of the slag pot
SU844781A1 (en) Method of repairing lock connection of blade with disc