NON-DESTRUCTIVE ANALYSIS PROCESS FOR A METAL ALLOY PART

Abstract

Method for non-destructive analysis of a metal alloy part, this part comprising a surface (14) having undergone at least one finishing treatment, the analysis method having the aim of verifying the conformity of the part after treatment, the method comprising the following steps: a) measurement of at least one color parameter and at least one gloss parameter of said surface (14), b) comparison of at least some of the measured parameters with previously determined reference parameters, and c) deciding on the conformity of the part according to the results of the comparison. Figure for the abstract: Figure 1

Description

Title of the invention: METHOD FOR NON-DESTRUCTIVE ANALYSIS OF A METAL ALLOY PART Technical field of the invention

[0001] The present invention relates to a non-destructive analysis method for a metal alloy part, this part comprising a surface having undergone at least one finishing treatment, the analysis method having the aim of verifying the conformity of the part after treatment. Technical background

[0002] The state of the art includes document FR-B1-3 065 072.

[0003] In the aeronautical industry in particular, treated metal alloy parts are used. This may, for example, be a steel-type alloy. The treatment of the part may aim to improve its surface condition or its properties, particularly mechanical properties.

[0004] For example, a steel part, such as a mechanical reducer part of an aircraft turbomachine, may undergo one or more of the following finishing treatments: thermochemical treatment, grinding machining, tribofinishing machining, and thin-film deposition. After each treatment, the treated surface of the part undergoes a change, for example in its appearance or surface condition.

[0005] There is a need to assess the conformity of such a part after treatment, in particular to determine whether the part has been properly treated and that a treatment has not been forgotten, for example. There is therefore a need for a method which makes it possible to verify that a treatment range for a part has been respected and has therefore been carried out in accordance with specifications.

[0006] The present invention provides a solution to this need, which is simple, effective and economical. Summary of the invention

[0007] The invention relates to a non-destructive analysis method for a metal alloy part, this part comprising a surface having undergone at least one finishing treatment, the analysis method having the aim of verifying the conformity of the part after treatment, the method comprising the following steps:

[0008] a) measurement of at least one color parameter and at least one gloss parameter of said surface,

[0009] b) comparison of at least some of the measured parameters with previously determined reference parameters, and

[0010] c) decide on the conformity of the part based on the results of the comparison.

[0011] The present invention thus proposes to measure two distinct parameters characterized characteristics of the surface condition of the part in order to determine whether this part is compliant or not. The first parameter measured relates to the color of the surface of the part, this color being in fact likely to change depending on the treatment undergone by the part. The second parameter measured relates to the gloss of the surface of the part, the gloss being also likely to change depending on the treatment of the part. A treatment of the part can result in a change in its color, or a change in its gloss, or a change in its color and gloss. By combining the measurement of the two parameters and comparing them to reference parameters, it is therefore possible to precisely define whether the part has undergone the treatment or not.Furthermore, in the case where the part is intended to undergo several successive treatments, it is even possible to determine which treatment(s) the part has (already) undergone and whether it has indeed undergone all the treatments it must undergo.

[0012] The method according to the invention may comprise one or more of the following characteristics or steps, taken in isolation from one another, or in combination with one another: • step a) includes the measurement of the color parameters L*, a* and b* in the color space L*a*b*; • step b) only includes the comparison of parameter a* or parameter b* or parameters a* and b* with previously determined reference parameters a* and / or b*; • step a) comprises measuring at least one brightness unit at at least one angle of incidence; • a brightness unit is measured at an angle of incidence of 20°, and / or 60°, and / or 85°; • step a) comprises the measurement of at least two, preferably at least five, and more preferably at least ten times the same color parameter(s) and the same gloss parameter(s), at several points of said surface (14), in order to determine an average of the measurements, or even a standard deviation, for each parameter, and in which the averages obtained are compared with the reference parameters in step b); • in step c), the part is considered to be compliant if the measured parameters are identical or close to the reference parameters, or non-compliant if the measured parameters are far from the reference parameters; the assessment of the terms “far” and “close” can be made by an experimental approach or according to the desired degree of confidence; • the part comprising a surface having undergone at least two or more treatments successive finishing treatments, the part is considered to be compliant if the measured parameters are identical or close to the reference parameters specific to the last finishing treatment undergone by the part, or non-compliant if the measured parameters are far from these reference parameters; • in step c), the part is considered compliant if each of the measured parameters is close to the corresponding average, considering the standard deviation of this average, or non-compliant if at least one of the measured parameters is far from the corresponding average, considering the standard deviation of this average; • the method comprises a preliminary step i) consisting of establishing an abacus comprising said reference parameters, step b) comprising the comparison of the measured parameters with the reference parameters of this abacus; • the reference parameters are established by carrying out the following sub-steps:

[0013] x) carrying out at least one finishing treatment on a surface of at least one reference part,

[0014] y) measuring at least one color parameter and at least one gloss parameter of said surface, and

[0015] z) complete the abacus with the measured parameters; • in step x), at least one part is prepared with at least one finishing treatment, at least one part is prepared with at least two successive finishing treatments, or even at least one part is prepared with at least three successive finishing treatments, and in which, in step y), the color and gloss parameters of the surface of each of these parts are measured; • in step x), at least one finishing treatment may be voluntarily omitted, that is to say that at least one part is prepared with at least one finishing treatment while omitting one or more additional finishing treatments, at least one part is prepared with at least two successive finishing treatments while omitting one or more intermediate finishing treatments, or even at least one part is prepared with at least three successive finishing treatments while omitting one or more intermediate finishing treatments; this makes it possible to have in step y), the color and gloss parameters of the surfaces of reference parts for which surface treatments have not been carried out; • step y) comprises measuring at least two, preferably at least five, and more preferably at least ten times the same color parameter(s) and the same brightness parameter(s), in several points of said surface, in order to determine an average of the measurements, or even a standard deviation, for each parameter, and in which the abacus is completed with these averages, or even these standard deviations, at step z); • the or each finishing treatment is chosen from a thermochemical treatment, for example carburizing, nitriding, grinding machining, tribofinishing machining, and thin layer deposition; • the part is made of a metal alloy, for example steel;

[0016] — the thin layer is deposited by PVD (acronym for physical vapor deposition) or PACVD (plasma assisted chemical vapor deposition) or PECVD (plasma enhanced chemical vapor deposition) or any other known thin film deposition method;

[0017] — the thin layer is partially transparent;

[0018] — the standard deviation represents approximately 3% of the value of the parameter considered; this value could be adjusted depending on the alloys considered. Brief description of the figures

[0019] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0020] [Fig-1] [Fig.l] is a block diagram illustrating steps of a method according to the invention;

[0021] [Fig.2] [Fig.2] is a schematic representation of a measurement of a color parameter of the surface of a part;

[0022] [Fig.3] [Fig.3] is a schematic representation of the L*a*b* color space;

[0023] [Fig.4] [Fig.4] is a schematic representation of a measurement of a parameter of gloss of the surface of a part;

[0024] [Fig.5] [Fig.5] is a graph showing measurements of a gloss parameter at several angles of incidence of parts having undergone different treatments;

[0025] [Fig.6] [Fig.6] is a graph showing measurements of color parameters of parts that have undergone different treatments; and

[0026] [Fig.7] [Fig.7] is a graph showing measurements of another color parameter of parts that have undergone different treatments. Detailed description of the invention

[0027] [Fig.l] shows a block diagram or flowchart comprising steps of a method according to the invention for non-destructive analysis of a metal alloy part.

[0028] The part in question is for example a part of a mechanical reducer of an aircraft turbomachine, although this example is not limiting.

[0029] The part is for example made of steel, that is to say an alloy based on iron and carbon.

[0030] The part has a surface which has undergone at least one finishing treatment and the analysis method aims to verify the conformity of the part after treatment.

[0031] Only a part of the part can be treated, or its entirety. It is therefore understood that the treated surface can be one of the surfaces of the part or its entire surface.

[0032] The treatment of the part aims in particular to improve its surface condition or its properties, for example mechanical.

[0033] By way of example, the part may for example undergo one or more of the following treatments (which are carried out successively one after the other or one after the other when the number of these treatments is at least equal to two): a thermochemical treatment for example of cementation or nitriding, machining by grinding or milling, tribofinishing or superfinishing, and a thin layer deposition.

[0034] [Fig.l] illustrates steps of the method according to the invention, some of which are optional.

[0035] The process can be done manually or automatically.

[0036] Essentially, the method according to the invention comprises three steps a), b) and c).

[0037] In step a), at least one color parameter and at least one parameter are measured of the surface gloss of the part.

[0038] In step b), at least some of the measured parameters are compared with previously determined reference parameters.

[0039] In step c), the conformity of the part is determined based on the results of the comparison in the previous step.

[0040] [Fig.2] illustrates the measurement of a color parameter in step a).

[0041] Preferably, this step a) comprises the measurement of the color parameters L*, a* and b* in the color space L*a*b*. This measurement can be obtained using a colorimeter 10, previously calibrated and placed on the surface to be measured. The colorimeter 10 is generally in the form of a small box. The colorimeter 10 comprises an emitter 12 which emits light to the surface 14, and a receiver 16 which receives the reflected light for analysis by the colorimeter or an analysis device associated with the colorimeter 10. In practice, the reflected light passes through three filters: red, green and blue, which distill the trichromatic values ​​(RGB) corresponding to the way our eyes see color.

[0042] The L*a*b* color space is schematically represented in [Fig.3] and is well known in the field of colorimetry.

[0043] In this color space, the location is done using Cartesian coordinates: L* indicates the luminance, while the parameters a* and b* are the chromaticity coordinates. The luminance L* takes values ​​between 0 (black) and 100 (reference white). The parameter a* represents the value on a green —> red axis, and the parameter b* represents the value on a blue —> yellow axis.

[0044] As will be described in more detail below, step b) may comprise only the comparison of the parameter a* or the parameter b* or the parameters a* and b* with previously determined reference parameters a* and / or b*. In other words, the luminance L is not necessarily used in the context of the present invention.

[0045] [Fig.4] illustrates the measurement of at least one brightness parameter in step a).

[0046] Preferably, this step a) comprises the measurement of at least one brightness unit (UB) at least one angle of incidence.

[0047] By definition, brightness is the measurement of the quantity of light reflected by a surface. This measurement can be obtained using a reflectometer 20 placed on the surface to be measured. The reflectometer 20 is in the form of a small box, for example. The reflectometer 20 comprises an emitter 22 which emits light to the surface 14, and a detector 24 which receives the reflected light for analysis by the reflectometer or an analysis device associated with the reflectometer 20.

[0048] The angle of incidence or illumination used greatly influences the value of the reflectometer 10. In order to be able to clearly differentiate between very shiny and matt surfaces, standardization has defined three geometries, or three measurement domains, respectively at the angles of incidence of 20°, 60° and 85°.

[0049] As illustrated in [Fig. 4], for a measurement at 20°, the emitter 22 and the detector 24 are located at 20° relative to an axis orthogonal to the surface 14, and located on either side of this axis. For a measurement at 60°, the emitter 22 and the detector 24 are located at 60° relative to an axis orthogonal to the surface 14, and located on either side of this axis. For a measurement at 85°, the emitter 22 and the detector 24 are located at 85° relative to an axis orthogonal to the surface 14, and located on either side of this axis.

[0050] In practice, the reflectometer 20 may comprise a series of three emitters 22 located respectively at 20°, 60° and 85°, and a series of three detectors 24 located respectively at 20°, 60° and 85°, so as to be able to carry out brightness measurements simultaneously or successively at these three angles, without moving or replacing the reflectometer 20.

[0051] Advantageously, step a) comprises the measurement of at least two, preferably at least five, and more preferably at least ten times the same color parameter(s) and the same gloss parameter(s), at several points on the surface 14, in order to determine an average of the measurements, or even a standard deviation, for each parameter. It is then understood that each average is compared to the reference parameters in step b).

[0052] In step c), the part can be considered as compliant if the measured parameters are identical or close to the reference parameters, or non-compliant if the pa measured parameters are far from the reference parameters. The assessment of the terms "far" and "close" can be made by an experimental approach or according to the desired degree of confidence.

[0053] In the aforementioned case where the part has undergone at least two or more successive finishing treatments, the part is considered to be compliant if the measured parameters are identical or close to the reference parameters specific to the last finishing treatment undergone by the part, or non-compliant if the measured parameters are far from these reference parameters.

[0054] The part is for example considered to be compliant if each of the measured parameters is located within the corresponding average, considering the standard deviation of this average, or non-compliant if at least one of the measured parameters is far from the corresponding average, considering the standard deviation of this average.

[0055] In practice, this means that the invention makes it possible to determine whether a part has undergone all the treatments that it should have undergone and to distinguish between parts that have undergone all the treatments and are therefore compliant, and parts that have not undergone all the treatments and are therefore non-compliant. For the latter parts that have not undergone all the planned treatments, the method can however make it possible to determine which treatments the part has already undergone. These aspects will be described in more detail below with reference to Figures 5 and following.

[0056] Advantageously, the method comprises a preliminary step i), i.e. before steps a) to c), consisting of establishing an abacus comprising the reference parameters. It is then understood that step b) comprises the comparison of the measured parameters with the reference parameters of this abacus.

[0057] The reference parameters are preferably established by performing the following sub-steps:

[0058] x) carrying out at least one finishing treatment on a surface of at least one reference part,

[0059] y) measuring at least one color parameter and at least one gloss parameter of said surface, and

[0060] z) complete the abacus with the measured parameters.

[0061] Preferably, in step x), at least one part is prepared with at least one finishing treatment, at least one part is prepared with at least two successive finishing treatments, or even at least one part is prepared with at least three successive finishing treatments.

[0062] In step x), at least one finishing treatment may be voluntarily omitted so that in the following step y) the parameters specific to this type of reference part are well known. For example, each reference part may be prepared with at least one finishing treatment by omitting one or more additional finishing treatments. comments.

[0063] Preferably, in step y), the color and gloss parameters of the surface of each of these parts are measured.

[0064] Preferably, step y) comprises the measurement of at least two, preferably at least five, and more preferably at least ten times the same color parameter(s) and the same gloss parameter(s), at several points on said surface, in order to determine an average of the measurements, or even a standard deviation, for each parameter.

[0065] Preferably, in step z), the chart is completed with these averages, or even these standard deviations.

[0066] In the above example, we therefore understand that this amounts to preparing several reference parts:

[0067] - a part without treatment,

[0068] - a part with thermochemical treatment,

[0069] - a part with thermochemical treatment and machining,

[0070] - a part with thermochemical treatment, machining, and finishing machining,

[0071] - a part with thermochemical treatment, machining, finishing machining, and deposition of a thin layer.

[0072] - or any other combination of the above steps, omitting one of the steps. For For each of these reference pieces, the color and brightness parameters are measured, preferably at several points, to obtain the averages and standard deviations. The abacus is filled in with these values.

[0073] When implementing the method, it is then possible to determine whether a part has undergone all the treatments it should have undergone and is compliant, or whether this is not the case.

[0074] For example, if a part which has undergone the various successive treatments (thermochemical treatment, machining, finishing machining and deposition of a thin layer) has color and gloss parameters measured in step a), which are consistent with the reference parameters for these successive treatments during step b), then this part is considered to be consistent with step c).

[0075] For example, if a part that is supposed to have undergone the various successive treatments (thermochemical treatment, machining, finishing machining and deposition of a thin layer) has color and gloss parameters measured in step a), which are not in accordance with the reference parameters for these successive treatments during step b) but which rather correspond to reference parameters of a previous treatment, then this part is considered as not conforming to step c) and is for example considered as not having undergone all the necessary treatments. The missing treatments could even be identified.

[0076] Figures 5 and following provide a better illustration of these latter aspects of the process.

[0077] [Fig.5] is a graph showing measurements of a gloss parameter at several angles of incidence of parts having undergone different treatments.

[0078] The graph includes the types of parts on the abscissa:

[0079] - part 30 is a part not thermochemically treated, but having undergone all machining and finishing operations, and coated with a thin layer deposit;

[0080] - part 32 is a part having undergone thermochemical treatment without post-machining treatment, and coated with a thin layer deposit;

[0081] - part 34 is a part having undergone thermochemical treatment, machining, but no finishing machining, and coated with a thin layer deposit;

[0082] - part 36 is a reference part, having undergone thermochemical treatment, a machining and finishing machining and coated with a thin layer deposit.

[0083] The graph includes on the ordinate the brightness unit which is here expressed as a percentage of brightness relative to the reference part 36.

[0084] For each type of part, there are three columns successively representing the measurements at 20°, 60° and 85° angle of incidence.

[0085] According to [Fig.5], by comparison with the brightness of the reference part 36, with a measurement angle of 20°:

[0086] - for part 30, the brightness is slightly lower than that of part reference 36;

[0087] - for part 32, the brightness is close to zero;

[0088] - for part 34, the brightness is reduced by more than half compared to that of reference part 36.

[0089] For the other brightness measurement angles (60°, 85°), these same trends are observable, but they are less marked.

[0090] We can therefore conclude that, for this example, the gloss parameters measured via an angle of 20° are the most discriminating for judging whether a part is compliant or not.

[0091] [Fig.6] is a graph showing measurements of color parameters (in this case L* and b*) of parts having undergone different treatments, and [Fig.7] is a graph showing measurements of another color parameter (in this case a*) of parts having undergone different treatments.

[0092] These graphs each include on the abscissa the types of parts 30 to 36 mentioned above.

[0093] The graphs include on the ordinate the percentage of the value of one of the parameters L*, a* or b* relative to the reference part 36.

[0094] In the graph of [Fig.6], there are two columns representing respectively the parameters L* and b* for each type of part, and in the graph of [Fig.7] there is a single column for each part type representing the parameter a*.

[0095] According to [Fig.6], by comparison with the chromatic spectrum of the reference part 36:

[0096] - the parameter a* is significantly lower compared to the reference part 36 for the room 32;

[0097] - the parameter b* is significantly lower compared to the reference part 36 for the room 34, and slightly lower for room 30;

[0098] - for the parameter L*, there is no strong variation depending on the type of part.

[0099] We can therefore conclude that, for this example, the color space parameters a* and b* are the most discriminating for judging whether a part is compliant or not.

Claims

Claims

1. Non-destructive analysis method for a metal alloy part, this part comprising a surface (14) having undergone at least one finishing treatment, the analysis method having the aim of verifying the conformity of the part after treatment, the method comprising the following steps: a) measurement of at least one color parameter and at least one gloss parameter of said surface (14), b) comparison of at least some of the measured parameters with previously determined reference parameters, and c) deciding on the conformity of the part based on the results of the comparison.

2. The method of claim 1, wherein step a) comprises measuring the color parameters L*, a* and b* in the color space L*a*b*.

3. Method according to claim 2, in which step b) comprises only the comparison of the parameter a* or the parameter b* or the parameters a* and b* with previously determined reference parameters a* and / or b*.

4. Method according to one of the preceding claims, in which step a) comprises measuring at least one brightness unit at at least one angle of incidence.

5. A method according to claim 4, wherein a brightness unit is measured at an angle of incidence of 20°, and / or 60°, and / or 85°.

6. Method according to one of the preceding claims, in which step a) comprises the measurement of at least two, preferably at least five, and more preferably at least ten times the same color parameter(s) and the same gloss parameter(s), at several points of said surface (14), in order to determine an average of the measurements, or even a standard deviation, for each parameter, and in which the averages obtained are compared with the reference parameters in step b).

7. Method according to one of the preceding claims, in which, in step c), the part is considered to be compliant if the measured parameters are identical or close to the reference parameters, or non-compliant if the measured parameters are far from the reference parameters.

8. Method according to one of the preceding claims, in which, the part comprising a surface which has undergone at least two or more successive finishing treatments, the part is considered to be compliant if the measured parameters are identical or close to the reference parameters specific to the last finishing treatment undergone by the part, or non-compliant if the measured parameters are far from these reference parameters.

9. Method according to claim 7 or 8, in combination with claim 6, in which, in step c), the part is considered to be compliant if each of the measured parameters is close to the corresponding average, considering the standard deviation of this average, or non-compliant if at least one of the measured parameters is far from the corresponding average, considering the standard deviation of this average.

10. Method according to one of the preceding claims, in which it comprises a preliminary step i) consisting of establishing an abacus comprising said reference parameters, step b) comprising the comparison of the measured parameters with the reference parameters of this abacus.

11. Method according to claim 10, in which the reference parameters are established by carrying out the following sub-steps: x) carrying out at least one finishing treatment on a surface of at least one reference part, y) measuring at least one color parameter and at least one gloss parameter of said surface, and z) completing the chart with the measured parameters.

12. Method according to claim 11, wherein, in step x), at least one part is prepared with at least one finishing treatment, at least one part is prepared with at least two successive finishing treatments, or even at least one part is prepared with at least three successive finishing treatments, and wherein, in step y), the color and gloss parameters of the surface of each of these parts are measured.

13. Method according to claim 11 or 12, in which step y) comprises the measurement of at least two, preferably at least five, and more preferably at least ten times the same color parameter(s) and the same gloss parameter(s), at several points of said surface, in order to determine an average of the measurements, or even a standard deviation, for each parameter, and in which the chart is completed with these averages, or even these standard deviations, in step z).

14. Method according to one of the preceding claims, in which the or each finishing treatment is chosen from a thermochemical treatment, for example carburizing, nitriding, grinding machining, tribofinishing machining, and thin layer deposition.

15. Method according to one of the preceding claims, in which the part is made of a metal alloy, for example steel.

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