Method for determining crack propagation rate of nickel-based alloy welding seam stress corrosion cracking

Abstract

The invention provides a method for determining the crack propagation rate of nickel-based alloy weld stress corrosion cracking, which comprises the following steps: S1, preparing a nickel-based alloy test plate with the same specification and welding process as an actual service component, and welding different areas on the nickel-based alloy test plate; s2, calculating an index n of a stress field intensity factor K; s3, calculating a CGR coefficient alpha and an index beta of HV or sigma s; s4, calculating activation energy Q; s5, a CGR model expression for unifying SCC of different areas of the nickel-based alloy weld joint is obtained; wherein CGR is the crack growth rate, HV is the Vickers hardness, and sigma s is the yield strength. The invention develops a new model for directly predicting the SCC CGR of each region of the welding seam according to the Vickers hardness (HV) or yield strength (sigma s) field test result of each region in combination with a stress field intensity factor (K). After the model is established, the CGR of the corresponding part can be obtained only by carrying out Vickers hardness or ball indentation test on different parts on site to obtain HV or sigma s, and data required by evaluation are more accurately and directly provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of crack propagation rate prediction, in particular to a method for determining the stress corrosion cracking crack propagation rate of a nickel-based alloy weld joint. BACKGROUND

[0002] A large amount of nickel-based alloy is used in the primary circuit equipment of light water reactor (LWR) nuclear power plants, such as reactor pressure vessel in-vessel components, steam generator water chamber partition plates, primary circuit main equipment safety ends, etc., and the main materials include INCONEL 600 (UNS06600, NC15Fe), 690 (UNS06690, NC30Fe) and corresponding welding materials 82 / 182 (ERNiCr-3 / ENiCrFe-3), 52 / 152 (ERNiCr-7 / ENiCrFe-7) and the like.

[0003] Since the typical service environment of the nickel-based alloy of the nuclear power plant, including the base material, the weld joint and the heat-affected zone, is the primary coolant, i.e. high-temperature and high-pressure water containing B / Li at a temperature of 292-327℃ and a pressure of 15.5MPa. With the extension of service time, stress corrosion cracking (SCC) may also occur under the long-term high-temperature and high-radiation environment.

[0004] SCC is a low-stress brittle fracture with strong concealment, and the weld joint and the heat-affected zone are the weak parts of the entire equipment due to the stress or strain caused by welding and structure, and the SCC thereof will seriously endanger the structural integrity of the main equipment and affect the safe and reliable operation of the nuclear power plant.

[0005] Therefore, the determination of the SCC propagation rate of the nickel-based alloy weld joint and the heat-affected zone under the complex organizational morphology caused by welding, irradiation and structure and the condition of large stress and strain is an important basis for the structural integrity evaluation and residual life assessment of the nickel-based alloy weld joint and the heat-affected zone.

[0006] On the other hand, although the crack propagation rate (CGR) formula of the nickel-based alloy such as 600, 82 and 182 is given in the nuclear power design specification, such as the ASME specification, the use of the formula requires the determination of the CGR coefficient and the stress field intensity factor exponent at the test temperature and the standard temperature. The recommended value can only represent the average value of the bulk material, and the changes of the SCC sensitivity and the CGR of the weld joint in each region caused by the changes of the structure, the stress and the strain cannot be truly reflected, so that the CGR of the weld joint in each region cannot be directly and accurately given, resulting in the deviation of the structural integrity evaluation and the residual life assessment.

[0007] Therefore, the present application inventors designed a method for determining the stress corrosion cracking crack propagation rate of a nickel-based alloy weld joint to overcome the above technical problems. SUMMARY

[0008] The technical problem solved by the present application is to provide a stress corrosion cracking crack growth rate determination method for nickel-based alloy welds in order to overcome the fact that the stress corrosion cracking (SCC) crack growth rate (CGR) model for nickel-based alloy welds in the primary loop high-temperature high-pressure water in the prior art fails to consider the influence of the microstructure of the weld, heat-affected zone, stress and strain changes on the actual SCC sensitivity and CGR of the weld, and thus cannot directly and accurately give the CGR of each region of the weld.

[0009] The present application solves the above technical problems by the following technical solutions:

[0010] A stress corrosion cracking crack growth rate determination method for nickel-based alloy welds, characterized in that the determination method comprises the following steps:

[0011] S1. Preparing a nickel-based alloy test plate of the same specification and welding process as the actual service component, and welding different regions on the nickel-based alloy test plate;

[0012] S2. Calculating the index n of the stress field intensity factor K;

[0013] S3. Calculating the index β of the CGR coefficient α and HV or σ s ;

[0014] S4. Calculating the activation energy Q;

[0015] S5. Obtaining a unified CGR model expression for the SCC of different regions of the nickel-based alloy weld;

[0016] wherein CGR is the crack growth rate, HV is the Vickers hardness, and σ s is the yield strength.

[0017] According to an embodiment of the present application, the CGR model expression in step S5 is

[0018] CGR=f(K,HV,T) or CGR=f(K,σ s ,T)

[0019] wherein T is the test temperature, K is the stress field intensity factor, HV is the Vickers hardness, and σ s is the yield strength.

[0020] According to an embodiment of the present application, the regions in step S1 include a B region, an H region and a W region, wherein the B region is a base material region, the H region is a heat-affected zone, and the W region is a weld region, and compact tension specimens are prepared by sampling.

[0021] According to an embodiment of the present application, step S2 comprises:

[0022] S 21, each region is tested under high temperature and high pressure water environment at a reference temperature T Ref Compact tension tests are carried out under different stress field intensity factors K1, K2, …, K n , and corresponding CGR1, CGR2, …, CGR n are obtained.

[0023] S 22 , logarithms logK1, logK2, …, logK n of different K values are linearly regressed with corresponding CGR logarithm values logCGR1, logCGR2, …, logCGR n , and a slope value obtained is an index n of K, and a power of 10 of an intercept of each region is a CGR coefficient α′ B , α′ H , and α′ W .

[0024] According to one embodiment of the present application, the step S3 comprises:

[0025] S 31 , Vickers hardness HV values of the B region, the H region, and the W region of the nickel-based alloy weld joint are obtained through a Vickers hardness test, or σs values σ sB , σ sH , and σ sW of each region are obtained through a ball indentation test.

[0026] S 32 , logarithm values of HV B , HV H , and HV W or σ sB , σ sH , and σ sW are linearly regressed with logα′ B , logα′ H , and logα′ W , and a slope value obtained is an index β of HV or σ s , and a power of 10 of an intercept obtained is a CGR coefficient α.

[0027] According to one embodiment of the present application, the step S4 comprises:

[0028] S 41 , after α, β, and n are determined, CT tests are simulated in a loop high temperature and high pressure water environment under the same region, the same K value, different temperatures T1, T2, …, T n , and CGR T1 , CGR T2 , …, CGR Tn under different temperatures are obtained.

[0029] S 42 , the log value of CGR at different temperatures logCGR T1 , logCGR T2 … logCGR Tn and linear regression, the slope value of the inverse, namely the activation energy Q.

[0030] According to an embodiment of the present application, the step S5 comprises:

[0031] The obtained α, β, n and Q are substituted into, that is, the unified CGR model is as follows:

[0032] or

[0033]

[0034] Wherein, α is the CGR coefficient, β is the HV or σ s exponent, n is the K index, Q is the activation energy, T is the test temperature, T Ref is the reference temperature, and R is the gas constant.

[0035] According to an embodiment of the present application, the reference temperature T Ref is 598K.

[0036] According to an embodiment of the present application, the gas constant R is 8.314 J / (mol·K).

[0037] The positive progress effect of the present application is that:

[0038] The nickel-based alloy weld stress corrosion cracking crack propagation rate determination method of the present application develops a new model for directly predicting the SCC CGR of each region of the weld according to the Vickers hardness (HV) or yield strength (σ s ) of each region on-site test results combined with the stress field intensity factor (K). After the model is established, only the HV or σ s of different parts on-site Vickers hardness or ball indentation test is needed to obtain the CGR of the corresponding parts, which more accurately and directly provides the required data for evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0039] The above and other features, properties and advantages of the present application will become more apparent through the following description with reference to the accompanying drawings and examples, in which the same reference numerals always denote the same features, and wherein:

[0040] Figure 1 is a flowchart of the nickel-based alloy weld stress corrosion cracking crack propagation rate determination method of the present application.

[0041] Figure 2 The figure shows the comparison between the measured value of the model and the predicted model curve in the method for determining the crack growth rate of the nickel-based alloy weld stress corrosion cracking. DETAILED DESCRIPTION

[0042] In order to make the above-mentioned objects, features and advantages of the present application more apparent, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0043] Reference will now be made in detail to the embodiments of the present application, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0044] In addition, although the terms used in the present application are selected from publicly known and used terms, some of the terms mentioned in the specification of the present application can be created by the applicant in his or her own judgment, and the detailed meanings thereof are described in relevant parts of the description herein.

[0045] In addition, the present application should not be understood merely based on the actual terms used, but also based on the meanings implied by each term.

[0046] As shown in Figure 1 and Figure 2 The present application discloses a method for determining the crack growth rate of nickel-based alloy weld stress corrosion cracking, which is a method for determining the unified crack growth rate (CGR) of stress corrosion cracking (SCC) in different regions of nickel-based alloy welds in light water reactor nuclear power plants, and comprises the following steps:

[0047] Step S1, preparing a nickel-based alloy test plate of the same specification and welding process as the actual service member, and welding different regions on the nickel-based alloy test plate.

[0048] Preferably, the regions in the step S1 include B region, H region and W region, wherein the B region is the base material region, the H region is the heat affected zone, and the W region is the weld zone, and compact tension specimens are prepared by sampling.

[0049] Step S2, calculating the index n of the stress field intensity factor K.

[0050] Preferably, the step S2 comprises:

[0051] Step S 21 , carrying out compact tension tests on each region under different stress field intensity factors K1, K2, …, K Ref at a reference temperature T n to obtain corresponding CGR1, CGR2, …, CGR n .

[0052] Step S22 logK1, logK2, …, logK n corresponding CGR logarithmic values logCGR1, logCGR2, …, logCGR n linear regression, the slope value obtained is the index n of K, and the intercept of each region is the power of 10, i.e. the CGR coefficient α′ of each region B α′ H and α′ W .

[0053] Step S3, calculating the CGR coefficient α and the index β of HV or σ s .

[0054] Preferably, the step S3 comprises:

[0055] Step S 31 , obtaining the Vickers hardness HV values of the B region, H region and W region of the nickel-based alloy weld by Vickers hardness test or obtaining the σs values σ sB , σ sH and σ sW .

[0056] Step S 32 , obtaining the logarithmic values of HV B , HV H and HV W or σ sB , σ sH and σ sW and logα′ B , logα′ H and logα′ W .

[0057] Step S4, calculating the activation energy Q.

[0058] Preferably, the step S4 comprises:

[0059] S 41 , after determining α, β and n, simulating CT test in a loop high-temperature high-pressure water environment at the same region, the same K value, different temperatures T1, T2, …, T n , obtaining CGR T1 , CGR T2 , …, CGR Tn .

[0060] S 42 , obtaining the logarithmic values logCGR T1, logCGR T2 … logCGR Tn With Linear regression is performed to obtain the slope value, and the inverse of the slope value, i.e. the activation energy Q, is obtained.

[0061] Step S5, obtaining a unified CGR model expression for different regions of the nickel-based alloy weld seam;

[0062] wherein CGR is the crack growth rate, HV is the Vickers hardness, σ s is the yield strength.

[0063] Preferably, the CGR model expression in step S5 is

[0064] CGR = f(K, HV, T) or CGR = f(K, σ s , T)

[0065] wherein T is the test temperature, K is the stress field intensity factor, HV is the Vickers hardness, σ s is the yield strength.

[0066] Preferably, the step S5 comprises:

[0067] The obtained α, β, n and Q are substituted into the unified CGR model as follows:

[0068] or

[0069]

[0070] wherein α is the CGR coefficient (m / s), β is the HV or σ s exponent, n is the K exponent, Q is the activation energy (J / mol), T is the test temperature (K), T Ref is the reference temperature, and R is the gas constant.

[0071] Preferably, the reference temperature T Ref is 598 K. The gas constant R is 8.314 J / (mol·K).

[0072] After the model is established, only the HV or σ s is obtained by performing Vickers hardness or ball indentation tests on different parts in the field, and the CGR of the corresponding part is obtained, thereby more accurately and directly providing the required CGR data for the structural integrity evaluation and residual life assessment of the component.

[0073] The following takes different regions such as the weld base material zone (B), the heat affected zone (H), and the weld zone (W) as examples, and the above parameters are determined through the following steps:

[0074] I. Respectively in nickel-based alloy weld B area, H area, W area sampling preparation compact tension (CT) sample.

[0075] And in reference temperature T Ref Under the simulated primary circuit high temperature and high pressure water environment, CT test of different K value K1, K2……K n , Obtain the logCGR1, logCGR2……logCGR n of different K value of each area. B , α′ H And α′ W' .

[0076] II. Through Vickers hardness test, obtain the HV value HV B , HV H And HV W of nickel-based alloy weld B area, H area, W area, or through ball indentation test to obtain the σ s Value σ sB , σ sH And σ sW . Linear regression of HV B , HV H And HV W Or σ sB , σ sH And σ sW And logα′ B , logα′ H And logα′ W Obtain the CGR coefficient α and the index β of HV or σs.

[0077] III. After determining α, β and n, through CT test under different temperature T1, T2……T n In the simulated primary circuit high temperature and high pressure water environment, obtain the logCGR T1 , logCGR T2 ……logCGR Tn of different temperature. And through linear regression Obtain the activation energy Q.

[0078] Through the calculation of the above three steps, the unified CGR model of nickel-based alloy weld base material area, heat affected zone and weld area can be obtained.

[0079] Similarly, a unified CGR model can also be established for various different areas through the above process. After the model is established, only through Vickers hardness or ball indentation test to obtain HV or σ sThe CGR of the corresponding part is obtained, and more accurate and direct data required for evaluation is provided.

[0080] The effect of the application is illustrated by taking the CGR of different regions of a 600 / 182 nickel-based alloy weld as measured by experiments as an example. Ref The index n of K is determined to be 2 by a series of experiments at a reference temperature T

[0081] The HV and σ s of different regions are determined by field Vickers hardness and ball indentation tests, and the CGR coefficient α' of different regions is as follows:

[0082] Table 1 HV, σ s and α' of different regions of a nickel-based alloy weld

[0083]

[0084] After taking the logarithm of HV or σ s and α' respectively, linear regression is performed to obtain α of HV as 1.20×10 -28 , β as 6.37, α of σ s as 3.55×10 -25 , and β as 4.33. Figure 2 As can be seen, the goodness of fit R 2 > 95%, indicating that the unified CGR model of SCC of different regions of a nickel-based alloy weld is in good agreement with the actual measured value. At this time, the obtained CGR model expression is:

[0085] Or

[0086]

[0087] Using the above model expression, the CGR of different regions of an actual component can be predicted by only measuring the HV or σ s of the actual component on site, thereby providing more accurate and direct data for evaluation.

[0088] The method for determining the stress corrosion cracking crack propagation rate of a nickel-based alloy weld of the application relates to the field of stress corrosion cracking crack propagation rate testing and life prediction of nickel-based alloys, and specifically relates to a method and a model for determining the stress corrosion cracking (SCC) crack propagation rate (CGR) of a nickel-based alloy and a weld and a heat-affected zone thereof of a light water reactor (LWR) nuclear power plant in a high-temperature and high-pressure water environment of a primary loop.

[0089] In summary, the method for determining the stress corrosion cracking crack propagation rate of a nickel-based alloy weld of the application develops a new method for determining the stress corrosion cracking crack propagation rate of a nickel-based alloy weld according to the Vickers hardness (HV) or yield strength (σ s) field test results combined with stress field intensity factor (K) directly predict the SCC CGR of each region of the weld. After the model is established, only by means of Vickers hardness or ball indentation test to obtain HV or σ s of the corresponding part, and more accurately and directly provides the data required for evaluation.

[0090] The above-described disclosure of the application is merely illustrative and does not limit the application. Although the application is not explicitly described, those skilled in the art can make various modifications, improvements and corrections to the application. Such modifications, improvements and corrections are suggested in the application, so such modifications, improvements and corrections still fall within the spirit and scope of the exemplary embodiments of the application.

[0091] Meanwhile, the application uses specific words to describe the embodiments of the application. As "one embodiment", "an embodiment", and / or "some embodiments" means a certain feature, structure or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that the "one embodiment" or "one embodiment" or "one alternative embodiment" mentioned in different places in the specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics of one or more embodiments of the application can be properly combined.

[0092] Similarly, it should be noted that, in order to simplify the description of the application disclosed herein and to help understand one or more embodiments of the application, sometimes multiple features are combined into one embodiment, figure or description thereof. However, this method of disclosure does not mean that the features required by the application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiments disclosed above.

[0093] Although the above describes specific embodiments of the application, those skilled in the art should understand that these are only illustrative, and the scope of protection of the application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the application, and such changes and modifications fall within the scope of protection of the application.

Claims

1. A method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds, characterized in that, The determination method includes the following steps: S1. Prepare nickel-based alloy test plates with the same specifications and welding processes as the actual service components, and weld different areas of the nickel-based alloy test plates. S2, Calculate the exponent n of the stress field intensity factor K; S3. Calculate the CGR coefficient α and HV or σ. s The exponent β; S4. Calculate the activation energy Q; S5. Obtain a unified CGR model expression for SCC in different regions of nickel-based alloy welds; Where CGR is the crack growth rate, HV is the Vickers hardness, and σ s It represents the yield strength.

2. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 1, characterized in that, The CGR model expression in step S5 is: CGR = f(K, HV, T) or CGR = f(K, σ s , T) Where T is the test temperature, K is the stress intensity factor, HV is the Vickers hardness, and σ is the stress intensity factor. s It represents the yield strength.

3. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 1, characterized in that, The regions mentioned in step S1 include region B, region H, and region W, where region B is the base material region, region H is the heat-affected zone, and region W is the weld zone. A compact tensile specimen is prepared by sampling.

4. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 3, characterized in that, Step S2 includes: S 21 Each region will be subjected to a high-temperature, high-pressure water environment with a reference temperature T. Ref Conduct research on different stress field intensity factors K1, K2...K n The compact tensile test was performed to obtain the corresponding CGR1, CGR2...CGR values. n ; S 22 Logarithms of different K values: log K1, log K2, ..., log K n The corresponding logarithmic values ​​of CGR are obtained as logCGR1, logCGR2, ..., logCGR. n Performing linear regression yields the slope value, which is the exponent n of K. The intercepts for each region, raised to the power of 10, are the CGR coefficients α′ for each region. B α′ H and α′ W .

5. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 4, characterized in that, Step S3 includes: S 31 The Vickers hardness (HV) values ​​of zones B, H, and W of nickel-based alloy welds can be obtained through Vickers hardness testing, or the σ values ​​of each zone can be obtained through ball indentation testing. s value σ sB σ sH and σ sW . S32, HV B HV H and HV W or σ sB σ sH and σ sW The logarithm of logα′ B ,logα′ H and logα′ W Performing linear regression yields the slope value, which is either HV or σ. s The exponent β is the intercept raised to the power of 10, which is the CGR coefficient α.

6. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 5, characterized in that, Step S4 includes: S 41 After determining α, β, and n, by using the same region, the same K value, and different temperatures T1, T2...T n CT experiments were conducted in a simulated high-temperature and high-pressure water environment to obtain CGR at different temperatures. T1 CGR T2 ......CGR Tn . S42. Calculate the logarithm of CGR at different temperatures using logCGR. T1 logCGR T2 ......logCGR Tn and Performing linear regression yields the negative of the slope value, which is the activation energy Q.

7. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 6, characterized in that, Step S5 includes: Substituting the obtained α, β, n, and Q into the formula yields the unified CGR model as follows: or Where α is the CGR coefficient, and β is HV or σ s The exponent, n is the K exponent, Q is the activation energy, and T is the test temperature. Ref Here is the reference temperature, and R is the gas constant.

8. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 7, characterized in that, The reference temperature T Ref It is 598K.

9. The method for determining the crack propagation rate of stress corrosion cracking in nickel-based alloy welds as described in claim 7, characterized in that, The gas constant R is 8.314 J / (mol·K).

Images