X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
1999-09-17
2001-04-17
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
Reexamination Certificate
active
06219404
ABSTRACT:
The present invention relates generally to a method of determining if an alloy article has any remaining working life, particularly to a method of determining if a nickel superalloy article for gas turbine engines has any remaining working life.
One of the main difficulties in determining if gas turbine engine components, particularly turbine blades and turbine vanes, have any remaining working life is that the gas turbine engines may be operated with different operating cycles. Hence a prediction of the service life of a gas turbine engine component is often made with little, or no, knowledge of the history of the use of the gas turbine engine component.
One known method of determining if gas turbine engine components have any remaining working life performs creep tests on a representative number of components. However, the resulting scatter in the test data makes the remaining working life estimate to be conservative.
An additional problem is that it is difficult to make allowances for the starting conditions of the gas turbine engine components. There may be a considerable variation in the initial microstructure of the gas turbine engine components because of the variability of the casting process.
Accordingly the present invention seeks to provide a method of determining if an alloy article has any remaining working life which reduces or overcomes the above mentioned problems.
Accordingly the present invention provides a method of determining if an alloy article has any remaining working life comprising the steps of:
(a) taking at least one sample from an alloy article,
(b) removing substantially all metal matrix material from the at least one sample to leave the carbide particles,
(c) analysing the carbide particles using x-ray diffraction, identifying the x-ray peaks of the main carbide phases from the x-ray diffraction spectra,
(d) determining the ratio, or difference, of the amount of a first carbide phase to the amount of a second carbide phase,
(e) providing a database containing the ratio, or difference, of the first carbide phase to the second carbide phase as a function of temperature of heat treatment and time of heat treatment,
(f) comparing the ratio, or difference, of the amount of the first carbide phase to the amount of the second carbide phase determined in step (d) with the database in step (e) to determine the temperature of heat treatment and the time of heat treatment of the sample of the alloy article,
(g) comparing the temperature of heat treatment and the time of heat treatment of the sample of the alloy article determined in step (f) with a plurality of different heat treatment temperatures and associated heat treatment times corresponding to the full working life of the alloy article to determine if the alloy article has any remaining working life.
Preferably step (d) comprises determining the ratio, or difference, of the amount of the M
23
C
6
carbide phase to the amount of the MC carbide phase.
Step (d) may comprise determining the ratio, or difference, of the amount of the M
23
C
6
carbide phase to the amount of the M
6
C carbide phase.
Step (d) may comprise determining the ratio, or difference, of the amount of the M
6
C carbide phase to the amount of the MC carbide phase.
Preferably step (d) comprises determining the ratio of the integrated intensity of the x-ray peak of the first carbide phase to integrated intensity of the x-ray peak of the second carbide phase.
Step (b) comprises dissolving substantially all the metal matrix material from the at least one sample in an electrochemical cell to leave the carbide particles.
Step (b) comprises dissolving substantially all the metal matrix material in an electrochemical cell having a solution comprising hydrochloric acid, tartaric acid and methanol.
Preferably the alloy article is a nickel base superalloy, a cobalt base superalloy or an iron base superalloy.
Preferably the alloy article is a turbine blade or a turbine vane.
Preferably step (a) comprises removing the sample from the leading edge of the turbine blade or turbine vane. Preferably step (a) comprises removing the sample from a predetermined position on the leading edge of each turbine blade or each turbine vane.
The alloy article may comprise an alloy comprising 10 wt % Co, 9 wt % Cr, 5.5 wt % Al, 10 wt % W, 2.5 wt % Ta, 1.5 wt % Ti, 1.5 wt % Hf, 0.15 wt % C and the balance Ni plus incidental impurities.
The alloy article may comprise an alloy comprising 16 wt % Cr, 8.5 wt % Co, 3.4 wt % Al, 2.6 wt % W, 1.7 wt % Ta, 3.4 wt % Ti, 1.7 wt % Mo, 0.8 wt % Nb, 0.11 wt % C and the balance Ni plus incidental impurities.
The alloy article may comprise 8.3 wt % Cr. 10 wt % Co, 0.7 wt % Mo, 10 wt % W, 3 wt % Ta, 5.5 wt % Al, 1 wt % Ti, 0.14 wt % C, 1.5 wt % Hf and the balance Ni plus incidental impurities.
REFERENCES:
patent: 5148458 (1992-09-01), Ruud
patent: 242 425 (1987-10-01), None
patent: 2201 733 (1988-09-01), None
Starink Marco J
Thomson Rachel C
Church Craig E.
Manelli Denison & Selter PLLC
Rolls-Royce plc
Taltavull W. Warren
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