The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades

Round 1

Reviewer 1 Report

In this work, a casting process of  DZ22B Superalloy Blades were simulated in a Procast, a casting simulating software, that allow prediction of defects and process design.   

 The aim is to estimate the effect of casting speed on the grain and dendrite growth.

 This manuscript is hard to follow, mainly because of many difficult-to-read sentences, and uncertainties.   

Some troubled sentences and plots highlighted in yellow with remarks are in the attached pdf manuscript file containing pop-up messages. Please answer one by one of those remarks.

Concerning uncertainties, I refer to:

·        The source of some experimental measurements (such as DSC plot) on casted turbine included in the manuscript is undefined. Please include in the experimental verification section, details about these measurements and the source of the blade specimens.

·        The interpretation of some real and simulated morphological-thermo graphic features  (Figs 13 to 18) is unconvincing. Please review this aspect.

·        The conclusion seems too short: it needs to be enhanced to include a brief description of the source of basic parameters for simulation, basic assumptions for simulation and the experimental verification strategy.  

In my opinion in the overall perspective, this manuscript has merit for publishing, provided a previous revision is completed.

Comments for author File: Comments.pdf

This manuscript is hard to follow, mainly because of many difficult-to-read sentences. I recommend a full proofreading review. 

Author Response

Dear Editor and reviewers,

Thank you for your letter and your comments and suggestions concerning our manuscript entitled “The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades”. Those suggestions are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and have made improvements according to your comments which are listed below. The changes are marked in blue in this revised paper. If there is any question, please feel free to contact us. Thanks for your consideration.

Sincerely yours

X.M. Wang

Professor of School of Materials Science and Engineering, Xiangtan University

Xiangtan, Hunan Province, 411105, People’s Republic of China

*Corresponding author. Tel: + 86 0731 18975228303

E-mail address: [email protected]

 

 

Reviewer #1:

In this work, a casting process of DZ22B Superalloy Blades were simulated in a Procast, a casting simulating software, that allow prediction of defects and process design.

The aim is to estimate the effect of casting speed on the grain and dendrite growth. Some troubled sentences and plots highlighted in yellow with remarks are in the attached pdf manuscript file containing pop-up messages. Please answer one by one of those remarks.

Point 1: This manuscript is hard to follow, mainly because of many difficult-to-read sentences.

Response:

Thanks for your comments, the English has been polished carefully. The changes made in the paper are highlighted in yellow. The main changes are as follows:

• Item 40-45, revised based on a suggestion from reviewer 1:

While the heat transfer coefficient of the mold shell and water-cooled crystallizer have constant values, the interfacial heat transfer coefficient between the casting and the mold shell changes with temperature according to the actual casting phase. For instance, in the solid phase range this coefficient is 600 W·m^-2·K^-1, value that increase in the melting process to a range of 600-1500 W·m^-2·K^-1, according to the solid-liquid proportion, above the liquid phase is 1500 W·m^-2·K^-1.

• Item 48-51, modified as:

In the actual directional solidification casting production, it requires a longer time for the entire directional solidification process which includes preheating and solidification cooling. Thus the form of multiple blades in one mold is generally used to improve the casting production efficiency.

• Item 56-64, modified as:

Firstly, the model was split into quarters by using the UG modeling software, due to the model structure is symmetrical. Then, considering the complexity of the turbine blade structure, the Visual-mesh model was used to segment the surface mesh.  The mesh was refined in the exhaust edge of the blade body and the small size of the truncated surface, to ensure that there are enough mesh layers in the cross-sectional thickness direction, as shown in Figure 2(b). Finally, the assembly of each part of the mesh was carried out after careful inspection and repair. The non-shaped shell surface and two symmetrical surfaces were specified. The thickness of the shell is set to 8mm, and the shell mesh is generated as shown in Figure 2(c).

• Item 66 and 67, revised based on a suggestion from reviewer 1:

 “solidification steps” and “takes place in a”

• Item 146-149, modified as:

The simulation results show that the dendrites have not fully grown when the pulling speed is too large. Moreover, too fast pulling speed resulted that growth direction of the casting changes because the thermal radiation direction of the blades is uncertain and the heat loss is excessive, leading the dendrites to be tilted.

• Item 149-151, modified according to reviewer 1 comments "with lower and diverging upper grains in the leaf, and eventually could originate transverse cylindrical crystals":

Too fast pulling speed will also make the growth of columnar crystals unstable, the upper part of the blade grain is few and divergent, and even transverse columnar crystals may appear.

• Item 154-155, revised based on comments from reviewer 1:

Adjusting the pulling speed is an artificially adjustable process to effectively change the cooling rate of castings, this change will...

• Item 158-159, revised based on comments from reviewer 1:

and it can be seen that the secondary dendrite spacing significantly decreases with an increase of pulling speed. 

• Item 220-222, revised based on comments from reviewer 1:

It can be seen that the dendrite orientation is disordered and the occlusion of the longitudinal secondary dendrite is inadequate.

• Item 222 and 238, modified as: “lower” and “significant”.
• Item 225-233, modified according to reviewer 1 comments "Please improve this sentence":

At the same time, large pulling speed will increase the solidification rate of the blades and the volume of solidified solids per unit of time, thus release more heat by the latent heat of crystallization. And then, it will decrease the negative temperature gradient parallel to the growth direction of the secondary dendrite and reduce the growth driving force, resulting in insufficient occlusion of the secondary dendrite. In addition, when the pulling speed is too fast, the radiation heat dissipation will be deviated from the directional solidification direction which can easily lead to oblique crystal and crystal-breaking defects. In short, excessive pulling speed will increase the tendency of alloy hot cracking.

• Item 310-313, modified as:

Through fluorescence non-destructive testing, no cracks were found at these three pulling rates, indicating that the change in pulling rate would not result in cracks. As shown in Figure 15, micorcracks can be observed in the microstructures which pulling rates are different. However, it should be noted that the crack size is significantly larger when the pulling rate is constant 6mm/min.

 

Point 2: The source of some experimental measurements(such as DSC plot)on casted turbine included in the manuscript is undefined. Please include in the experimental verification section, details about these measurements and the source of the blade specimens.

Response :

• Item 31, the Reviewer 1 comments "whose":

The casting material is DZ22B superalloy from first author affiliation of Aecc South Industry Company Limited, and the alloy composition is shown in Table 1.

 

• Item 35, “Which turbine blades (reference?)where used to obtain DSC plot using the DSC404E3 equipment?”

Firstly, in order to ensure the uniformity of the composition, the DSC sample is taken from the DZ22B master alloy, rather than the blade. Then, a sample of about 20mg is cut from the base metal of DZ22B alloy, and the DSC curve is measured by using the DSC404F3 differential scanning calorimeter in the School of Materials Science and Engineering of Xiangtan University.

 

• Item 112-117, "Which simulation parameters":

In order to investigate the effect of pulling speed on the temperature field of DZ22B superalloy blades during directional solidification, while keeping other simulation parameters such as shell wall thickness, thermal conductivity of the mold shell, interfacial heat transfer coefficient, shell temperature and insulation time unchanged. The ProCAST preprocessing module set the pulling speed to 2mm/min, 6mm/min, and 10mm/min, respectively. The temperature field simulation results obtained are shown in Figure 3.

• Item 178-181, “Do you refer to corrosion detected by a florescence detection method? In which conditions DZ22D corrosion takes place? During the casting process in contact with air”:

Experiments were conducted on blades with hot cracks produced by AECC Southern Industry Company Limited. The cracks were detected using fluorescence detection, while the macroscopic grain distribution was observed after the sample was corroded with hydrochloric acid. Corrosion is not used for fluorescent testing.

And the naming of Figure 7 was changed to: Fluorescence detection results of hot cracked blades and macroscopic grain corrosion results.

 

Point 3: The interpretation of some real and simulated morphological-thermo graphic features (Figs 13 to 18) is unconvincing. Please review this aspect.

 

Response:

• About figure 3 “Should it be: liquid phase fraction? instead of fraction solid”

It can be seen from Figure 3 (a) that the temperature of the blade gradually decreases from top to bottom, so the temperature at the bottom of the blade is lower，and the solid fraction is more. It can also be seen from the left color bar frame and corresponding figures in Figure 3 (b), that gray represents a larger solid fraction, and red represents a smaller solid fraction, which is consistent with the conclusion of temperature distribution. Therefore, Figure 3 (b) should represent the solid fraction.

 

• Item 290, “Why the hot cracking tendency is larger in b)? What visual aspects justify this attribute”：

The color bars and corresponding numbers on the left side of the simulated image indicate the trend of the simulation parameters. In Figure 14, purple represents a small tendency for thermal cracking, while red represents a large tendency for thermal cracking. It can be seen from Figure 14 that the variable speed pulling rate of 6mm/min-10mm/min is larger than the variable speed pulling rate of 6mm/min-2mm/min, and the dark blue region is larger and the purple region is smaller, indicating that the area with large thermal cracking tendency is wider. According to the simulation results of uniform pulling, it can also be seen that when the pulling rate is constant,...

 

• Regarding Figure 18, this image is blurry and has been changed to a sharper image.

Point 4: The conclusion seems too short: it needs to be enhanced to include a brief description of the source of basic parameters for simulation, basic assumptions for simulation and the experimental verification strategy.

 

Response: Based on your suggestion, the conclusion has been reorganized as follows:

DZ22B alloy is commonly used as a blade material for aircraft engines and gas turbines, and its preparation process is an important factor affecting the performance. In present work, a reliable numerical model has been established through ProCAST numerical simulation and auxiliary experimental verification methods. The effect of casting speed on the grain and dendrite growth of DZ22B superalloy blades is studied. Based on numerical simulation and experimental verification,  the following conclusions can be drawn:

(a)The simulation results show that the solid-liquid interface isotherm is convex at the pulling speed of 2mm/min, the solid-liquid interface is concave at the pulling speed of 10mm/min, the solid-liquid interface isotherm changes smoothly at the pulling speed of 6mm/min.

(b) The morphology of the mushy zone affects the growth trend of grains, and the speed of 6mm/min is more conducive to the growth of straight columnar crystals, which is consistent with the experimental results.

(c)Variable speed pulling can effectively reduce micro-cracks, thereby reducing the tendency of hot cracking. At the pulling speed of 6-2mm/min, the grain size is more uniform, and there are no abnormally developed secondary dendrites.

(d)Based on the above results, it is recommended to select 6-2mm/min variable pulling speed for the directional solidification of the DZ22B superalloy blade.

Author Response File: Author Response.docx

Reviewer 2 Report

The study titled 'The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades' presents a meticulously conducted investigation into the influence of pulling speed on the preparation process of DZ22B superalloy blades. The authors skillfully integrate numerical simulation techniques with experimental verification, yielding robust and comprehensive findings. I endorse this manuscript and accept it in its current form.

Author Response

Dear Editor and reviewers,

Thank you for your letter and your comments and suggestions concerning our manuscript entitled “The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades”. Those suggestions are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and have made improvements according to your comments which are listed below. The changes are marked in blue in this revised paper. If there is any question, please feel free to contact us. Thanks for your consideration.

Sincerely yours

X.M. Wang

Professor of School of Materials Science and Engineering, Xiangtan University

Xiangtan, Hunan Province, 411105, People’s Republic of China

*Corresponding author. Tel: + 86 0731 18975228303

E-mail address: [email protected]

 

 

Comments and suggestions:

The study titled 'The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades' presents a meticulously conducted investigation into the influence of pulling speed on the preparation process of DZ22B superalloy blades. The authors skillfully integrate numerical simulation techniques with experimental verification, yielding robust and comprehensive findings. I endorse this manuscript and accept it in its current form.

 

Response : Thanks for your comments.

Author Response File: Author Response.docx

Reviewer 3 Report

Review

1.   The authors report about the effect of pulling speed on grain and dendrite growth of DZ22B superalloy blades through experiment and numerical simulation. Based on the results obtained, the authors propose optimized regimes for the formation of a homogeneous defect-free structure in DZ22B alloys.

2.   First of all, I would like to note that the quality of the English language is at a good level. However, I would recommend authors to avoid complex and long sentences.

3.   The abstract fully reflects the goals and objectives of the study, and also briefly describes the main results of the authors.

4.   In general, the Introduction is well written. Here the authors explain in detail the choice of DZ22B material and the scope of its application.

5.   The quality of figures and captions to them should be improved. In particular, it is recommended to make small font larger and use the same type font. Figure captions also need to be structured and shortened. The informativeness of Figures 7 and 10 is questionable.

6.   The experimental and computational part of the paper is beyond doubt.

7.   Comments:

·       Item 134 ‒ write dot instead of semicolon.

·       Abbreviations as CA method and HTI must be deciphered in the paper.

·       Item 150 ‒ Incomplete term used. Did you mean secondary dendrite arm spacing (SDAS)?

·       Items 138, 158, 312, 317, 330 ‒ What does the word «tissue» mean? Maybe you mean structure instead «tissue»?

·       Item 178 ‒ I think it's better to write like this «SEM images of the blade pores after corrosion process were obtained at various pulling speeds (Fig. 8 and Fig. 9).»

8.   The paper mainly cites Chinese authors. Are Russian, American and European scientists not involved in the study of DZ22B superalloys and the problems of their manufacture?

 

In general, after above improvements, the paper can be recommended to the Materials journal.

Comments for author File: Comments.pdf

In general, the quality of the English language is at a good level. However, I would recommend authors to avoid complex and long sentences.

Author Response

Dear Editor and reviewers,

Thank you for your letter and your comments and suggestions concerning our manuscript entitled “The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades”. Those suggestions are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and have made improvements according to your comments which are listed below. The changes are marked in blue in this revised paper. If there is any question, please feel free to contact us. Thanks for your consideration.

Sincerely yours

X.M. Wang

Professor of School of Materials Science and Engineering, Xiangtan University

Xiangtan, Hunan Province, 411105, People’s Republic of China

*Corresponding author. Tel: + 86 0731 18975228303

E-mail address: [email protected]

 

 

Reviewer #3:

Point 1: First of all, I would like to note that the quality of the English language is at a good level. However, I would recommend authors to avoid complex and long sentences.

Response 1: Thanks for your comments, the English has been polished carefully. The changes made in the paper are highlighted in yellow. The main changes are as follows:

(Item 47-50) In the actual directional solidification casting production, it requires a longer time for the entire directional solidification process which includes preheating and solidification cooling. Thus the form of multiple blades in one mold is generally used to improve the casting production efficiency.

(Item 55-63) Firstly, the model was split into quarters by using the UG modeling software, due to the model structure is symmetrical. Then, considering the complexity of the turbine blade structure, the Visual-mesh model was used to segment the surface mesh.  The mesh was refined in the exhaust edge of the blade body and the small size of the truncated surface, to ensure that there are enough mesh layers in the cross-sectional thickness direction, as shown in Figure 2(b). Finally, the assembly of each part of the mesh was carried out after careful inspection and repair. The non-shaped shell surface and two symmetrical surfaces were specified. The thickness of the shell is set to 8mm, and the shell mesh is generated as shown in Figure 2(c).

(Item 145-148) The simulation results show that the dendrites have not fully grown when the pulling speed is too large. Moreover, too fast pulling speed resulted that growth direction of the casting changes because the thermal radiation direction of the blades is uncertain and the heat loss is excessive, leading the dendrites to be tilted.

(Item 224-228) At the same time, large pulling speed will increase the solidification rate of the blades and the volume of solidified solids per unit of time, thus release more heat by the latent heat of crystallization. And then, it will decrease the negative temperature gradient parallel to the growth direction of the secondary dendrite and reduce the growth driving force, resulting in insufficient occlusion of the secondary dendrite. In addition, when the pulling speed is too fast, the radiation heat dissipation will be deviated from the directional solidification direction which can easily lead to oblique crystal and crystal-breaking defects. In short, excessive pulling speed will increase the tendency of alloy hot cracking.

(Item 302-306) Through fluorescence non-destructive testing, no cracks were found at these three pulling rates, indicating that the change in pulling rate would not result in cracks. As shown in Figure 15, micorcracks can be observed in the microstructures which pulling rates are different. However, it should be noted that the crack size is significantly larger when the pulling rate is constant 6mm/min.

 

Point 2: item 134-write dot instead of semicolon.

Response 2: item 134 is now item 141, and already changed to dot.

 

Point 3: Abbreviations as CA method and HTI must be deciphered in the paper.

Response 3: item 86 and item 95, revised based on comments from reviewer 3: CA(correspondence analysis) and hot tearing indicator(HTI).

 

Point 4: item 150-Incomplete term used. Did you mean secondary dendrite arm spacing (SDAS)?

Response 4: item 150 is now item 156, and it should be secondary dendrite arm spacing (SDAS).

 

Point 5: items 138, 158, 312, 317, 330-What does the word “tissue” mean? Maybe you mean structure instead “tissue”?

Response 5: item 138, 158, 312, 317 is now item 145, 164, 323, 329-and already changed “tissue” to “structure”.

 

Point 6: 178-I think it's better to write like this “SEM images of the blade pores after corrosion process were obtained at various pulling speeds (Fig.8 and Fig.9)”.

Response 6: item 178 is now item 186, and now changed to SEM images of the blade pores after corrosion process were obtained at various pulling speeds (Figure 8 and Figure 9).

 

Point 7: The paper mainly cites Chinese authors. Are Russian, American and European scientists not involved in the study of DZ22B superalloys and the problems of their manufacture?

Response 7: Russian, American and European scientists are also involved in the study of DZ22B superalloy and its manufacturing problems, such as Reference 2, Reference 13, Reference 24, Reference 26.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has certainly improved, but I still recommend some minor English corrections in several parts of the text.  

 In the conclusion, I suggest this minor modification:

“In the present work a reliable numerical model have been established through ProCast numerical simulation that assumes a set of fixed operating and thermo physical parameters and complemented with auxiliary experimental verification method.”

In my opinion, the scientific content is relevant and deserve to be published

In several parts of the text there are some minor corrections  to be made in order to improve the  english writing.

Author Response

Dear Editor and reviewers,

Thank you for your letter and your comments and suggestions concerning our manuscript entitled “The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades”. Those suggestions are all valuable and very helpful for revising and improving our paper. We have studied the comments carefully and have made improvements according to your comments which are listed below. The changes are marked in blue in this revised paper. If there is any question, please feel free to contact us. Thanks for your consideration.

Sincerely yours

X.M. Wang

Professor of School of Materials Science and Engineering, Xiangtan University

Xiangtan, Hunan Province, 411105, People’s Republic of China

*Corresponding author. Tel: + 86 0731 18975228303

E-mail address: [email protected]

 

 

Reviewer #1:

The manuscript has certainly improved, but I still recommend some minor English corrections in several parts of the text.

 

In the conclusion, I suggest this minor modification:

 

“In the present work a reliable numerical model have been established through ProCast numerical simulation that assumes a set of fixed operating and thermo physical parameters and complemented with auxiliary experimental verification method.”

 

In my opinion, the scientific content is relevant and deserve to be published

 

Response:

Dear reviewer, thank you for your valuable suggestion. Have you uploaded the PDF modification attachment? However, we did not see the " some minor English corrections in several parts of the text " you mentioned in the system.

We carefully checked the attachments you previously uploaded and found that item 142 ' and ' was not deleted and has been corrected. In addition, other minor English corrections you previously recommended have been revised.

Based on your suggestion, the conclusion is modified as follows:

“DZ22B alloy is commonly used as a blade material for aircraft engines and gas turbines, and its preparation process is an important factor affecting the performance. In the present work a reliable numerical model has been established through ProCast numerical simulation that assumes a set of fixed operating and thermo physical parameters and complemented with auxiliary experimental verification method. The effect of casting speed on the grain and dendrite growth of DZ22B superalloy blades is studied. Based on numerical simulation and experimental verification, the following conclusions can be drawn:

(a)The simulation results show that the solid-liquid interface isotherm is convex at the pulling speed of 2mm/min, the solid-liquid interface is concave at the pulling speed of 10mm/min, the solid-liquid interface isotherm changes smoothly at the pulling speed of 6mm/min.

(b)The morphology of the mushy zone affects the growth trend of grains, and the speed of 6mm/min is more conducive to the growth of straight columnar crystals, which is consistent with the experimental results.

(c)Variable speed pulling can effectively reduce micro-cracks, thereby reducing the tendency of hot cracking. At the pulling speed of 6-2mm/min, the grain size is more uniform, and there are no abnormally developed secondary dendrites.

(d)Based on the above results, it is recommended to select 6-2mm/min variable pulling speed for the directional solidification of the DZ22B superalloy blade.”

Author Response File: Author Response.docx