JP2009300371A - Method and apparatus for detecting hetero-crystalline area of single crystal material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus, capable of nondestructively and simply detecting a hetero-crystalline area as a defect occurring in manufacturing a signal crystal metallic material or in use, even when existing in an invisible region. <P>SOLUTION: The method for detecting the hetero-crystalline area of the single crystal material comprises; a step of making an ultrasonic wave incident on the front face of an object to be inspected which is made of the single crystal material and has front and rear faces sandwiching a certain thickness part, and of detecting a reflected wave from the rear face; a step of measuring a time from the incidence to the detection of the rear-face reflected wave; a step of detecting the presence of the hetero-crystalline area, based on a deviance in detected times of the rear-face reflected wave measured at least two or more points (first method); and a step of detecting the presence of the hetero-crystalline area, based on a deviance of the detected time of the rear-face reflected wave from a detection time of the rear-face reflected wave estimated from previously obtained shape information of the object to be inspected (second method). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention measures non-destructively different crystal regions in a single crystal material (i.e., crystal orientation of the single crystal locally) by measuring the propagation time of the ultrasonic wave propagating in the test object made of the single crystal material. Alternatively, the present invention relates to a method and an apparatus for detecting a region where a tissue is different from the surrounding area.

In many cases, it is necessary to detect a different crystal region in a single crystal material for quality inspection, maintenance and operation of a product made of the single crystal material. For example, in recent years, single crystal alloys have been used in the moving blades and stationary blades of many aircraft jet engines and gas turbines for power generation. In these single crystal parts, a different crystal region often occurs in the manufacturing stage (for example, a crystallization process by slow cooling of a single crystal material, or a part manufacturing process by cutting a crystallized single crystal material). Alternatively, a different crystal region may occur due to a recrystallization phenomenon caused by damage during operation (for example, a dent due to collision of a foreign substance). The different crystal region significantly lowers the strength of the material and is difficult to repair, so parts with different crystals are discarded. Therefore, it is necessary to detect these different crystal regions by inspection. Known detection methods for different crystal regions in a single crystal material include a macro etch method in which the entire outer surface of a part is etched and observed, a Laue method in which the part is irradiated with X-rays and evaluated from a diffraction pattern, or the like Microscopic observation method in which a part is cut out and observed with a microscope after polishing / etching, and EBSP method (electron backscattering) in which the electron irradiated to the cut out sample is evaluated by backscattering diffraction image formed by backscattering Diffraction image method). However, both methods require considerable labor and time. In addition, the macro-etching method can only be applied to the visible outer surface of the part; the Laue method is difficult to inspect the entire part; the microscopic and EBSP methods cannot be inspected without destroying the part; There is. As described above, there have been problems with conventional methods for detecting different crystal regions, particularly in Ni-based single crystal alloys used in high-temperature equipment.
JP 2008-58244 A

  The present invention has been made to solve the above-described problems of the prior art, and the existence of a different crystal region in an object to be inspected such as a part made of a single crystal material is nondestructively and easily It is a main object to provide a method and apparatus capable of being detected, including those that are not visible.

  The inventors of the present invention have proposed a crystal orientation measuring apparatus and measurement method that pay attention to the fact that the propagation speed of incident ultrasonic waves differs depending on the crystal orientation of a single crystal material (Patent Document 1). As a result of studying for the above-mentioned purpose, the present inventors have reached the knowledge that by developing the method of Patent Document 1, it is possible to detect a different crystal region in a single crystal material. That is, the method for detecting a different crystal region of a single crystal material according to the present invention comprises a single crystal material, and an ultrasonic wave is incident from the front surface of the object to be inspected having a front surface and a rear surface sandwiching a certain thickness, and from the rear surface. A step of detecting a reflected wave; a step of measuring a time from the incident to the detection of the back surface reflected wave; and a detection of the presence of a different crystal region based on a difference in the back surface reflected wave detection time measured at at least two locations. The presence of a different crystal region is detected based on the difference between the back surface reflected wave detection time estimated from the back surface reflected wave detection time and the shape information of the inspected object obtained in advance (first method). And a step (second method).

  The apparatus for detecting a different crystal region of a single crystal material according to the present invention includes an ultrasonic wave generation / detection unit, and a surface that is electrically connected to the ultrasonic wave generation / detection unit and sandwiches a certain thickness of the single crystal material. A time measuring means for measuring a time from when an ultrasonic wave is incident from the front surface of the inspection object having a back surface until a reflected wave from the back surface is detected; and the time data electrically connected to the time measuring means Storage means, a calculation means electrically connected to the storage means, and a visualization means electrically connected to the calculation means.

  The detection principle of the different crystal region in the method and apparatus of the present invention is different from the detection principle based on the action as an ultrasonic reflection surface brought about by the scratch as in the general ultrasonic flaw detection method, and the basis of the invention of the above-mentioned Patent Document 1. Based on the phenomenon that the propagation speed (sound speed) of an incident ultrasonic wave differs depending on the crystal orientation of a single crystal material, and more generally, the sound speed in a substance is proportional to the square root of its Young's modulus. Thus, the different crystal region is detected through a change in time from the incidence of the ultrasonic wave incident on the single crystal material and reflected from the back surface to the detection of the back surface reflected wave.

For example, a Ni-based single crystal superalloy known as a heat-resistant alloy has a face-centered cubic lattice crystal structure (that is, at the center of each lattice plane in addition to the lattice origin of the cubic lattice on one side a) as shown in FIG. , A crystal structure having an equivalence point represented by a specific atom such as Ni), which is solidified while being pulled up in the uniaxial direction (vertical direction in FIG. 1 (a)) [001] As shown in FIG. 1B (upper plan view of the crystal lattice of FIG. 1A), two directions [100] and [010] orthogonal to each other on the (001) plane orthogonal to [001] V _[100] = V _[010] <v _[110] (= between the propagation speeds of the ultrasonic waves incident on the single crystal from each direction of [110], which is an intermediate direction of 45 degrees from each direction. It is known that the relationship of about 1.3 × V _[100] ) is established.

  In a general ultrasonic flaw detection method, as shown in FIG. 2, prior to a detection peak Pi (t = 0) accompanying ultrasonic incidence and a detection peak Pr (tr) accompanying back-surface reflection of the object to be inspected, When a detection peak Pf (tf <tr) of a reflected wave from another defect appears, a flaw or another defect is detected. On the other hand, in the method for detecting a different crystal region according to the present invention, the interface between the different crystal region and the normal crystal region does not act as an ultrasonic reflection surface. If the data such as the shape of the single crystal material and the crystal orientation dependence of the ultrasonic wave propagation speed are accurately grasped, it is slightly deviated from the original detection peak Pr (tr) associated with the back surface reflection of the object to be inspected. This is based on the knowledge that the presence of a different crystal region existing in the thickness direction can be detected based on the back surface reflection peak.

  Hereinafter, embodiments of the method and apparatus for detecting a different crystal region of a single crystal material according to the present invention will be described with a gas turbine rotor blade / stator blade mainly made of a Ni-based single crystal superalloy known as a heat-resistant alloy in mind. The description will be given with reference.

<First Embodiment>
First, the first embodiment will be described below assuming a single crystal solidified in the z direction (the z-axis is [001] in the solidification direction), for example (mainly in claims 1 to 8). Correspondence). The probe 2 is brought into contact with the surface of the inspection object 1 as shown in FIG. The probe 2 includes an ultrasonic wave generation / detection unit 21 and a holding unit 22 (FIG. 4A). Examples of the ultrasonic wave generation / detection unit 21 include a piezoelectric element made of ceramic or polymer. The present invention is not limited to this, and any apparatus that can generate and detect ultrasonic waves may be used. The holding means 22 holds the ultrasonic wave generation / detection means 21 and acts so as to stably contact the surface of the object 1 to be inspected, and may be any material such as resin or metal. It is desirable that the end surface of the probe 2 is brought into contact with the surface of the device under test 1 via a lubricating medium such as glycerin. Alternatively, the inspection object may be immersed in water, and ultrasonic waves from the probe 2 may be incident on the inspection object 1 in a non-contact manner using water as a medium. In order to improve the detection accuracy of different crystal regions, it is desirable that a plurality of ultrasonic wave generation / detection means 21 be regularly arranged. As shown in FIG. 4B, the ultrasonic wave generation / detection means 21 causes the ultrasonic wave to be incident on the object 1 to be detected and the reflected wave is detected. The ultrasonic wave generation / detection means 21 is connected to the time measurement means 4 via the signal transmission means 3, and the time measurement means 4 measures the time from the incidence of the ultrasonic wave to the detection of the reflected wave. The measured time information is stored in the storage unit 5 together with position information y = y1 in the moving direction (y) of the probe 2. Next, the probe is moved in the y direction, and the time from the incidence of the ultrasonic wave to the detection of the reflected wave is similarly measured with y = y2, and stored in the storage means 5. The stored information is calculated by the calculation means 6, and the output is displayed as a graph as shown in FIG. 3B on the visualization means 7 such as various displays. At this time, if the different crystal region CA exists at the position of y = y2, even if the shape of the non-inspection object is constant regardless of y as in the example of FIG. There is a difference in the time until wave detection (deviation between ◯ and x in FIG. 3B). The presence of the different crystal region can be detected by this difference. As described above, the speed of sound in a substance is generally proportional to the square root of its Young's modulus. Accordingly, if even a part of a different crystal region exists in a part made of a single crystal, the speed of sound changes in that part. This method uses this principle to detect different crystals. Naturally, y collects data not only for the above two points but also for the entire necessary inspection area of the non-inspection object 1.

  Preferably, a component (inspected object) database 8 storing shape information such as a thickness distribution (profile) of the component to be inspected is connected to the calculating means 6, and the information is obtained by the calculating means 6 as necessary. It is configured to be readable. It is also possible to detect a different crystal region by drawing a thickness profile obtained from information on the part shape on a graph of time from incident to reflected wave detection and comparing the measured plots. Although the absolute value of the time from incident to reflected wave detection varies for each single crystal material (main crystal orientation) constituting the part or for each material, in this example, for example, a profile at a certain y value ( The relative positional relationship of the plots does not change. Therefore, the profile read from the part database 8 may be a thickness profile obtained from the shape information, and can be freely moved up and down on the display, and can be compared and evaluated by superimposing with the actual measurement plot.

  Here, the storage means 5 and the parts database 8 are constituted by, for example, a data storage device such as a hard disk device and a memory, and the time measurement means 4 and the calculation means 6 and the information storage device via the external output interface and the external input interface. Communication is possible. The calculation means 6 is constituted by a computer, for example, and operates each program stored in a hard disk device or the like by a calculation unit such as a CPU to perform calculation. As specific examples of the calculation, (a) calculating an ideal time t from the design wall thickness data and sound velocity data stored in the database 8, (b) “difference between y = y1 data and y = y2 data. And (c) calculating the “difference” between the measured time data and the time data calculated in (a) above. Each means described above may include, for example, a keyboard or a mouse for inputting information as a data input unit. Further, the visualization means is constituted by, for example, a liquid crystal display. Or the visualization means to the paper medium like a printer may be sufficient.

  Incidentally, when the time data is collected by the probe 2, the x-direction arrangement interval of the ultrasonic wave generation / detection means 21 in the arranged probes at the x-direction positions x1, x2... With respect to the required plot interval. When (x2−x1) is wide, the ultrasonic wave generation / detection unit 21 is slightly moved in the x direction within a range within the interval of the ultrasonic wave generation / detection unit 21 at a constant y (Δx <x2−x1). Thus, in addition to the original positions x = x1, x = x2..., Time data is collected at additional positions such as x = x1 + Δx, x = x2 + Δx... And stored together in the storage means 5. The calculation means 6 may integrate the plot data with high density.

<Second Embodiment>
Next, a second embodiment will be described. That is, unlike the first embodiment, an example in which the ultrasonic incident surface 11 of the inspection object 1 is a curved surface or has irregularities is shown.

In this embodiment, as shown in FIG. 5, the probe 2 includes an ultrasonic wave generation / detection unit 21, a tube 23 that supports the ultrasonic wave generation / detection unit 21, a holding unit 22 that holds the tube 23, and a stopper 24 attached to the signal transmission unit 3. ing. Further, an elastic member 25 is sealed inside the tube 23 and is mechanically connected to the ultrasonic wave generation / detection means 21. The holding means 22 has a role of dynamically connecting adjacent pipes 23 and is made of resin, metal, or the like. The elastic member 25 in the tube 23 is made of rubber, a metal spring, or the like, so that the probe 2 (the ultrasonic wave generation / detection means 21) can follow the shape of the object 1 to be inspected. It has become. The tube 23 may be made of either metal or resin, but it is desirable that a low friction material such as Teflon be disposed on the inner surface (contact surface with the ultrasonic wave generation / detection means). The tube 23, the stopper 24, and the elastic member 25 function as auxiliary holding means for the ultrasonic wave generation / detection means 21 in the probe 2.

<Third Embodiment>
A third embodiment will be described with reference to FIG. As in the second embodiment, this embodiment is suitable when the ultrasonic incident surface of the device under test 1 is a curved surface or has irregularities. As shown in FIG. 6, the ultrasonic wave generation / detection means 21 of the probe 2 in water and the inspection object 1 are inspected by immersing the inspection object 1 in a medium such as water 30 for inspection. By using the probe 2 having the distance maintaining means 26 for keeping the distance from the ultrasonic incident surface 11 constant, the underwater distance can be kept constant.

<Fourth Embodiment>
The fourth embodiment relates to a method of complementing fluctuations in evaluation values in consideration of changes in sound speed due to crystal orientation. Taking the object to be inspected 1 and a cylindrical coordinate system on a hollow cylinder with a constant thickness formed by the unidirectional solidification method in the [001] direction as shown in FIG. 7A, for example, FIG. Both the method of arranging the probe in the θ direction and scanning in the z direction and the method of arranging the probe in the z direction and scanning in the θ direction as shown in (c) are suitable. Used for.

  Here, in the former case, the graph of time data obtained is as shown on the right side of FIG. That is, a result greatly different from the thickness profile obtained only from the shape information of the object to be inspected stored in the parts database can be obtained. This is due to the anisotropy of the single crystal material part, and the θ scan around the cylindrical material surrounding the [001] direction axis is the same as shown in FIGS. 1 (a) and 1 (b). [100] → [110] → [010]... In order of crystal materials, which corresponds to incident ultrasonic waves in different crystal orientation directions, and has a slow ultrasonic propagation speed based on the difference in crystal orientation [100]. And in the [010] direction, the back surface reflection time becomes long, and in the [110] direction where the propagation speed is fast, the back surface reflection time becomes short. In such a case, it is possible to easily detect the presence / absence of an abnormality by calculating and displaying a difference between adjacent z data (z = z1 and z = z2) at each θ. At that time, the profile displayed with reference to the parts database is also displayed corresponding to the difference between adjacent z's. (Note that the horizontal straight line shown as the design thickness profile in FIG. 7B represents the profile only with the design shape without considering the crystal orientation. Is displayed to indicate that they do not match at all.

  Unlike the example of FIG. 7B, as shown in FIG. 7C, a direction in which anisotropy does not easily occur in data collection of one row of the probe may be selected. In this case, the absolute value varies depending on θ, but the profile matches that of the parts database (in this example, constant reflection time data based on uniform thickness).

7B and 7C, information on the crystal orientation of the component (the crystal orientation of the component and the relationship between the crystal orientation and the sound velocity) is given to the component database 8 and the calculation means 6. Thus, not a comparison of two or more types of actually measured data, but a theoretical profile of time from incident to reflected wave detection considering the crystal orientation (for example, a theoretical profile corresponding to z = z2 in FIG. In the example, it is approximated to a measured profile of z = z1) or a theoretical profile corresponding to the profile of θ = θ2 in FIG. 7C (in this example, θ = θ1 and θ = is calculated and displayed) (for example, a profile or graph of z = z2 in FIG. 7B). 7 (c) may be compared with θ = θ2). The calculation of the theoretical profile is based on the assumption that the part (inspected object) is a single-crystal material with no defects. This is done by taking into account changes in sound speed. Regarding the change of the ultrasonic propagation velocity (sound speed) depending on the crystal orientation, for example, sound speed data (for example, V _[100] , V _{[210 ]} in a typical crystal orientation of a typical Ni-based superalloy having a face-centered cubic lattice structure. _], V _[110], sound velocity data in the V _[111], etc.), and other intermediate orientation are stored in the component database 8. Only the sound speed data in the representative direction may be stored in the database 8, and the sound speed data in the intermediate direction may be derived by interpolation.

  The above-described detection mode of the different crystal region by comparing the theoretical profile with the actually measured reflection time profile is not a simple profile like a straight cylindrical part with a constant wall thickness as shown in FIG. 7, but a more complicated shape. This is preferable in order to improve the detection accuracy of the different crystal region in the profile. For example, in the comparison between measured data at two positions, it is assumed that the theoretical profiles between the two match, and unless one of them is assumed to be correct, a different crystal region cannot be detected. This is because the different crystal regions can be detected by comparing the theoretical data profile and the actual measurement data at each position without using the comparison between the measurement data. This is different from the ultrasonic flaw detection method that enables clear detection such as detection of reflected waves based on scratches, and improves the detection accuracy of different crystal regions according to the method of the present invention based on the time lag of subtle reflected waves. Above is an important advantage.

<Fifth Embodiment>
In the above embodiment, the ultrasonic wave generation / detection means 21 arranged in a row has been described as an example. However, by using one ultrasonic wave generation / detection means, the incidence of ultrasonic waves is repeated while shifting its position. It is also possible to carry out a method for detecting a different crystal region according to the method of the present invention by detecting the reflected wave. In this case, there is an advantage that a narrow region can be inspected and the apparatus can be simple and inexpensive. Specifically, for example, the same inspection as described above can be performed by scanning the probe as shown in FIG. 8A (the holding means and the like are omitted in the figure). On the contrary, a structure in which a plurality of rows of ultrasonic wave generation / detection means are arranged instead of one row may be employed (FIG. 8B). In this case, there is an advantage that a large area can be inspected quickly.

  Although the above embodiment has been described with an example in which the moving blades and stationary blades of a gas turbine made of a single crystal superalloy having a face-centered cubic structure are taken into consideration, there are various other embodiments within the scope of the present invention. It will be readily appreciated by those skilled in the art that various forms are possible.

  As described above, according to the present invention, a non-destructive region including a case where a different crystal region as a defect that occurs during production or use of a single crystal metal material is present in a region that cannot be visually observed, Provided are a method and an apparatus that can be easily detected.

(a) is a schematic perspective view of a face-centered cubic lattice structure of a single crystal material by a uniaxial [001] direction solidification method, and (b) is an upper plan view of the lattice structure. The graph of the detection pattern of the reflected wave in the general ultrasonic flaw detection method. (a) The block diagram of the detection apparatus which concerns on this invention, (b) An example of the display of the test result which concerns on this invention. (a) And (b) is a schematic diagram which shows the structure of the ultrasonic probe which concerns on this invention. (a)-(c) is a schematic diagram which shows the structure of the ultrasonic probe which concerns on this invention. The schematic diagram which shows the structure of the ultrasonic probe which concerns on this invention. (a)-(c) is a schematic diagram which shows the inspection method which considered material anisotropy based on this invention. (a) And (b) is a schematic diagram which shows the structure and scanning method of the ultrasonic probe which concerns on this invention.

Explanation of symbols

1: Inspected object (11: ultrasonic wave incident surface, 12: ultrasonic wave reflecting surface, CA: different crystal region)
2: Probe 21: Ultrasonic wave generation / detection means 22: Holding means 23: Tube 24: Stopper 25: Elastic member 26: Distance maintenance means 3: Signal transmission means 4: Time measurement means 5: Storage means 6: Calculation means 7: Visualization means 8: parts (inspected object) database

Claims (11)

A step of detecting an reflected wave from the back surface of the object to be inspected made of a single crystal material having a surface and a back surface sandwiching a certain thickness, and detecting the back surface reflected wave from the incident And a step of detecting the presence of a different crystal region based on a difference between the back surface reflected wave detection times measured at at least two locations. Crystal region detection method. A step of detecting an reflected wave from the back surface of the object to be inspected made of a single crystal material having a surface and a back surface sandwiching a certain thickness, and detecting the back surface reflected wave from the incident And the presence of the different crystal region is detected based on the difference between the step of measuring the time until and the back surface reflected wave detection time and the back surface reflected wave detection time estimated from the shape information of the object to be inspected in advance. A method for detecting a different crystal region of a single crystal material. The single-sided calculation method according to claim 2, wherein when the back surface reflected wave detection time is estimated from the shape information of the inspected object obtained in advance, the calculation is performed with reference to the crystal orientation information of the inspected object. A method for detecting a different crystal region of a crystal material. An ultrasonic wave is incident from the surface of the object to be inspected having an ultrasonic wave generation / detection unit and a surface and a back surface that are electrically connected to the ultrasonic wave generation / detection unit and sandwich the thickness of a single crystal material. A time measuring means for measuring a time until a reflected wave from the back surface is detected, a storage means electrically connected to the time measuring means and storing the time data, and electrically connected to the storage means A device for detecting a different crystal region of a single crystal material, comprising: a calculation means; and a visualization means electrically connected to the calculation means. The apparatus for detecting a different crystal region of a single crystal material according to claim 4, comprising at least two ultrasonic wave generation / detection means. 6. The apparatus for detecting a different crystal region of a single crystal material according to claim 4 or 5, further comprising a parts database electrically connected to the calculation means and storing shape information of the object to be inspected. 7. The apparatus for detecting a different crystal region of a single crystal material according to claim 6, wherein information on crystal orientation is stored in the parts database together with shape information of the object to be inspected. The apparatus for detecting a different crystal region of a single crystal material according to any one of claims 4 to 6, further comprising holding means for holding the ultrasonic wave generation / detection means. The apparatus for detecting a different crystal region of a single crystal material according to claim 8, wherein the holding unit includes a deformable material and has a structure capable of changing a direction of the ultrasonic wave generation / detection unit. A tube that supports the ultrasonic wave generation / detection means, and an elastic member that mechanically joins the ultrasonic wave generation / detection means and the tube, the relative relationship between the ultrasonic wave generation / detection means and the tube The apparatus for detecting a different crystal region of a single crystal material according to claim 9, wherein the positional relationship is variable. 9. The apparatus for detecting a different crystal region of a single crystal material according to claim 8, further comprising a distance maintaining unit capable of maintaining a constant distance between the ultrasonic wave generation / detection unit and the object to be inspected.

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