FR2516943A1 - PROCESS FOR INCREASING THE RELIABILITY OF A SET OF BUILDING PARTS, IN PARTICULAR TURBINE BLADES - Google Patents

Abstract

A. THE PROCESS IS INTENDED TO INCREASE THE RELIABILITY OF A SET OF CONSTRUCTION PARTS, IN PARTICULAR TURBINE BLADES, WHICH HAVE ALREADY BEEN TAKEN BY CREEP FORCES. B. THE PARTS WHICH HAVE ALREADY HAVE BEEN UNDER THE FORCES OF CREEP TO A HOT ISO-STATIC COMPRESSION, WHICH CLOSES THE PORES AND CRACKS WHICH HAVE OCCURRED. C. THIS TREATMENT ALLOWS TO INCREASE THE DURATION OF COMMISSIONING OF THE SERIES OF CONSTRUCTION PARTS, IN PARTICULAR TURBINE BLADES.

Description

Method for increasing the reliability of a

  set of construction parts, in particular from

besides turbines ".

  The invention relates to a control method for increasing the reliability of a set of construction parts already stressed by creep forces, in particular parts provided with a

  coating plating, such as turbo blades

motors and turbines.

The structural parts

  creep, usually made of metal,

  are subject, in their implementation, to modifications

  material cations These include training

  separations, the roughness of these decol-

  deformation of these detachments as a function of thermodynamic equilibrium, as well as formation of creep pores and cracks. A superposition of these various effects leads, as a general rule, to failure of the structural component by fracture at

course of time.

If it is not possible to verify

  without material destruction of such pieces of construction once implemented, it is generally resorted to control research of the

  internal structure on a representative test sample.

  This process is, however, affected in some ways by

  insecurity, which are mainly

  in the taking of the sample This process is particularly

  initially unsatisfactory for the evaluation of the remaining life of turbine blades because, due to the large number of turbine crown blades, the

  likelihood of damage or modification

  important structural features are not detected by the test sample, can not be reduced

  as much as desired, for economic reasons.

  The present invention aims to increase the reliability of a set of pieces of

  construction as defined above.

  For this purpose, the subject of the invention is a control method characterized in that the parts of construction already stressed by creep forces are subjected to a pressing operation.

isostatic hot.

Thanks to this isostatic pressing

  hot, that is to say to this heat treatment under pres-

  isostatic pressure, with a view to increasing the reliability

  of all the construction parts, the modifications

  material structures to which creep-stressed structural parts have been subjected are largely removed, so that these parts can be put back into service after this treatment. In addition, for parts provided with

  plating veneer, and also with a view to

  of the reliability of the assembly, this isostatic pressure makes it possible to carry out a verification or an execution check

  simple as regards the sorting of the parts of the en-

  seems to be followed by more precise

if we.

The invention provides various forms of

  The embodiments of the invention are described below. Closing of the creep pores and cracks is achieved in non-coated construction parts, as long as the pores and cracks do not extend to the outer surface of the part. in composite construction parts, that is to say

  having one or more layers and / or

  In many cases, closure is often achieved when

  pore and creep fissures extend to the over-

  outer face of the base material (pores and cracks

exterior of base material).

  Thanks to the realization of this closure of the pores and cracks according to the invention, the service life of the component is increased by the hot isostatic pressing operation,

  provided that cracks do not arrive on the surface

  This increase in duration frequently amounts to at least 50%, for example in the case of nickel-based forged alloys which consist essentially, for example, by weight of 14% of chromium. about 1.2% titanium, about 5% aluminum, about 20% cobalt, about% molybdenum, about 1% silicon, about 1% manganese, about 2% iron, about 0.2% of

carbon, and about 50% nickel.

If such a product is submitted,

  in particular, at a high isostatic pressure, especially greater than 1250 bars, to modify the solution structure of the components of the alloy, with a view to homogenization and reduction of the separations, the mechanical strength, the tensile strength , the

  ductility (elongation) and vibration resistance

  in time, are increased especially in nickel-forged alloys. For example, in

2516943-

  the case of a nickel-based forged alloy with the proportions of components mentioned above,

  gets an increase in the possibility of distortion

  in the notch impact test of 400%, with increased tensile strength.

The use of relative temperatures

  lower, below the

  solution by melting the base material, gives the pos-

  the possibility of hot isostatic pressing of structural parts with a coating plating, without ineffective embrittlement and diffusion effects occurring in the plating, and / or in the base material. the veneer of the base material before proceeding to

hot isostatic pressing.

  The coating veneer covers and conceals the external cracks of the base material, so that they can only be detected with a very high expense of means.

  hot isostatic pressing, according to the invention

  they are closed, as indicated above, or otherwise, they open under the effect of pressing, which allows to detect a crack formation in the coating This opening, that is to say the tear coating outside the outer crack of the base material, is a good preparation for

  verification, or even an easy check to perform.

  Thus, the cracks are now made visible with a microscope. The conclusion of this observation then leads, according to whether the size of crack is inadmissible or acceptable, to an exchange of this piece.

  of construction or its conservation as a whole.

  This avoids the risk of maintaining parts of con-

  too heavily damaged, for example by

  return to service of defective turbine blades.

16943

The parameters of isostatic pressing

  According to the invention, the temperature range is such that the temperature is equal to the plating temperature of the coating, i.e., less than the melting solution temperature of the base material, and the isostatic pressure is about between 950 and 2000 bar, the pressing time being approximately four hours, in the case of the nickel-based alloy with the percentages of component mentioned above, and with a layer of aluminum applied by

  diffusion, the treatment temperature is approximately

  ron 10500 C and the isostatic pressure at around 1300

  bars, the pressing time being 1.5 hours.

In the set of parts mentioned

  born, or crown of blades of turbo engine or turbine, it is primarily blades, a gas turbine in particular But the building parts mentioned at the beginning can be also, for example, fittings

elbows or curved pipes.

  The raw material or basic material of the building parts mentioned at the beginning

  is usually a metal or a metal alloy,

  a nickel-based alloy.

  truction can be made up of, for example, one

  first or a base material of exceptional hardness: in particular the mentioned turbine blades are thus made.

of a nickel-based alloy.

In the case of

  truction provided with a plating mentioned at the beginning, the coating is for example a layer of aluminum or chromium deposited by diffusion, or a plated layer,

  such as, for example, a layer of cobalt-chromium

  aluminum ytrium, an insulating layer of heat,

-2516943

  for example zirconium oxide (Zr 20), or the super-

  position of at least two of these layers

  firstly the turbine blades mentioned are provided

a coating of this kind.

Claims (6)

CLAIMS R E V E M D I C A T I 0 N S   1) Process for increasing the reliability of a set of construction parts, already stressed by creep forces, in particular parts provided with a coating, such as blades or vanes of turbo-motors and turbines, characterized in that the construction parts already   creep are subjected to iso- static hot.   2) Process according to the claim   1, characterized in that the hot isostatic pressing has the effect of closing the pores due to creep and cracks. 3) Process according to one of the   claims 1 and 2, characterized in that by a   high isostatic pressure, especially greater than 1250 bar, the solution behavior of the elements   of alloy is modified, in the sense of homogeneity   and a reduction in separations. 4 d Process according to one   conque of claims 1 to 3, characterized in that,   in the case of parts with a coating veneer   hot isostatic pressing is carried out at a temperature below the melting temperature of the basic material.  ) Process according to the claim   cation 1, characterized in that, if the cracks ex-   the base material is not closed by   hot isostatic pressing, the veneer is   here, which allows the crack to be detected for the purpose of scrapping the building in question. 6) Process according to any one   one of claims 1 to 5, characterized in that   that in this hot isostatic pressing, the temperature   is approximately equal to the plating temperature of the coating and less than the melting temperature   in solution of the base material, the isostatic pressure   that being between about 950 and 2000 bar, and the pressing time of up to about 4 hours.   7) Process according to the claim   6, characterized in that, in the case of a nickel-based forged alloy as the base material of the construction part, with a diffusion layer or   a plated layer, this temperature is included in   at 950 and 1150 ° C, the isostatic pressure is between 1200 and 1400 bar and the pressing time is between 1 and 2 hours.