Effect of Heat Treatment and Test Temperature on the Strength Properties of Cast Heat-Resistant Nickel Base Inconel 718 Superalloy under Shock-Wave Loading
and Svetlana A. Atroshenko 3
Round 1
Reviewer 1 Report
A very interesting article, prepared correctly, with a logical justification of the proposed scope and the research performed. The prepared analysis and the formulated conclusions are justified. In my opinion, the article can be published.
Author Response
The authors are grateful to the reviewer for his kind attitude and comments to our manuscript. Thank you very much.
Reviewer 2 Report
The effect of heat treatment on the resistance to deformation and fracture of the Inconel 718 structural superalloy under shock-wave loading at room and 650 oC are carried out. The results under high speed loading are meaningful.
The research about the shock loading mechanical property test should be reviewed.
The organization of the paper should be improved, such as proper arrangement of the equaitions and figures, detailed discription of shock test with figures and photos.
The shock experiment device, sample and impactor should be illustrated. The sizes of samples and impactors. and the photos of samples after shock experiment.
please give the spall fracture photo or illustration. please compare the spall fractures.
Why different impactor thickness is applied?
Give the subtitles of each sub figure. please mark these variables
on the figure.
It maybe meaningless of Fig. 5, because the impactor thickness changes with sample thicknes.
The scale of x and y is not uniform in FIg. 5. The axis of Fig.7 should be clearly denoted in log scale.
The maximum thickness of the samples is 4mm, where is Fig.9 taken? It seems far thicker than 4mm. what is the direction of shock? Please show the area location in the samples.
The explanation of Fig.9 is hard to understand. Please mark the phases and cracks on FIg.
What is the spall plate? What is V and V0 in the strain rate?
Note some units maybe in Russian, HRD is not a unit. And expession of the thickness like 28794 µm.
Author Response
The authors are grateful to the reviewer for his kind attitude and useful and constructive comments and advice that will undoubtedly help to improve this manuscript.
The organization of the paper should be improved, such as proper arrangement of the equaitions and figures, detailed discription of shock test with figures and photos.
– In the structure of the manuscript we followed the recommendations of the editorial board as the IMRaD (Introduction, Methods, Results, and Discussion) and consider the article to follow this structure.
The shock experiment device, sample and impactor should be illustrated. The sizes of samples and impactors. and the photos of samples after shock experiment.
– Shock-wave experiments performed in this work on a pneumatic gun are quite typical for such studies, a fairly complete description of these experiments is made in the manuscript, indicating the sizes of samples and impactors and other features of experimental assemblies. In an article we have just published in the same journal on the dynamic properties of the additively manufactured Inconel 718 alloy, we gave a scheme of experiments and a photo of the equipment [Andrey S. Savinykh, Gennady V. Garkushin, Sergey V. Razorenov, Svetlana A. Atroshenko, Olga G. Klimova-Korsmik and Nikita G. Kislov. Strength Properties of the Heat-Resistant Inconel 718 Superalloy Additively Manufactured by Direct Laser Deposition Method under Shock Compression. Metals, 2022, 12, 967. https://doi.org/10.3390/met12060967]. We have added a link to this article in the description of the experiments (paragraph 2.4 [17]). We couldn't do this earlier, as the article was published after we submitted this manuscript to Metals
please give the spall fracture photo or illustration. please compare the spall fractures.
– In Fig. 9, we presented photographs of the spall zone of the initial samples at normal and elevated temperature up to 650 C in order to compare them and show the effect of temperature on the morphology of the spallation. Such a spall pattern is typical for these measurements and for heat-treated samples, so we did not provide such photos for all heat-treated samples
Why different impactor thickness is applied?
– One of the goals of this work was to investigate the effect of the strain rate on the spall strength of the alloy under study after preliminary heat treatment according to different modes. The strain rate of the material before fracture depends on the duration of the compression pulse, which in turn depends in our case on the thickness of the impactor, the thinner the impactor, the higher the strain rate of the material. By changing the thickness of the impactor from 0.2 to 1 mm, we managed to change the strain rate by about an order of magnitude
Give the subtitles of each sub figure. please mark these variables on the figure.
– For each sub-figure (Fig.1.), the caption to the figure indicates the state of the alloy in accordance with Table 2.
It maybe meaningless of Fig. 5, because the impactor thickness changes with sample thicknes.
– The decay of the elastic precursor depends on the thickness of the sample, i.e. on the distance traveled by the elastic wave and does not depend on the thickness of the impactor. The shock load pulse can be generated in any way - by detonation, pulsed laser action, etc. If the sample has an elastic-plastic deformation character, then in all cases an elastic wave is formed before the plastic compression wave, regardless of the loading conditions.
The scale of x and y is not uniform in FIg. 5. The axis of Fig.7 should be clearly denoted in log scale.
– In Fig.5, the scale of the X and Y axes is really different, but this is done to maximize the use of the field of the figure. This practice is generally accepted; especially often it is done when lagorithmic coordinates are used, as in our case. In our opinion, it is clearly visible that the axes in Fig.7 have a logarithmic scale.
The maximum thickness of the samples is 4mm, where is Fig.9 taken? It seems far thicker than 4mm. what is the direction of shock? Please show the area location in the samples.
– As can be seen from the scale ruler (1 mm) shown in Figure 9, the width of the specified field does not exceed 3 mm. Of course, this is the cut-out main fragment of the photo of the spall zone obtained on a perpendicular slice of the recovered sample with a thickness of 4 mm. We see a perpendicular section of the sample, the loading of which was carried out perpendicular to the visible plane. The figure shows the spall zone along the entire width of the sample. Arrows indicating the direction of impact have been added to the Fig.9.
The explanation of Fig.9 is hard to understand. Please mark the phases and cracks on FIg.
– The spall cracks and pores are marked in Fig. 9
What is the spall plate? What is V and V0 in the strain rate?
– The spall plate is the result of the spallation - internal fracture of the sample. The spall fracture occurs inside the sample due to tensile stresses arising after the reflection of the shock wave from the free surface of the sample (in our case). The inner breaking divides the sample into two parts (two plates), the outer of which is called a spall plate. Its thickness depends on many parameters of the experiment - the thickness of the impactor and the sample, the material of the impactor and the sample, the velocity of impact, etc.
V is the current specific volume of the substance, V0 is the specific volume of the substance at zero pressure. In fact, the strain rate in our case is the rate of expansion of matter.
94 µm.¸7´8¸Note some units maybe in Russian, HRD is not a unit. And expession of the thickness like 2
– HRD is not a unit of measurement, it is a commonly accepted abbreviation for Rockwell-measured hardness, which is dimensionless
Reviewer 3 Report
Shock-wave experiments on Inconel 718 alloy was carried out to discuss effect of heat treatment and impacting temperature on the properties of interest. Since the shock-wave response of the alloy has rarely been reported, the data provided in the manuscript could be a valuable reference for researchers in the field. Therefore, the manuscript could be published. Before publication, the followings could be improved by the authors.
It is highly recommended for the authors to consult to a professional English proofreader. Overall it is difficult to understand what authors intend to deliver. It is because of poor English writing, but it is also because of careless writing itself. Therefore, not only English proofreading, but also very careful proofreading by the authors is necessary.
Once defined numbers such as 650 degree C should be consistently used throughout the manuscript. In some part, authors used "649 degree C" which could confuse readers.
In the figure caption for Figure 1, what each figure a, b, c, and d shows should be defined.
In defining twin direction and size, the strange method used in the manuscript, for example, "2/8x7/94", should be explained and properly defined.
"bulk module B" to "bulk modulus B".
It would be good to add a new figure describing the shock-wave experiment detailing the shape of impactor and specimen.
"inconel 738" to "inconel 718".
In the discussion, only 'Hugoniot elastic limit' and 'spall strength' are discussed. However, the meaning and actual implications of those two factors are missing. Therefore, discussion on that aspect with (1) the relationship between microstructure and those two factors, (2) physical meaning of those two factors, (3) effects of those two factors on possible application, and (4) direction of improvement that should be achieved for the alloy to be used in a specific future application could be added.
Author Response
The authors are grateful to the reviewer for his kind attitude and useful and constructive comments and advice that will undoubtedly help to improve this manuscript.
– In the structure of the manuscript we followed the recommendations of the editorial board as the IMRaD (Introduction, Methods, Results, and Discussion) and consider the article to follow this structure.
Once defined numbers such as 650 degree C should be consistently used throughout the manuscript. In some part, authors used "649 degree C" which could confuse readers.
– We heated our samples to 650C, as explained in paragraph 2.1, because at a temperature of 649C, standard static measurements of the characteristics of this alloy are carried out. The technical features of conducting shock wave experiments on a pneumatic gun with heating of samples do not allow for the collision of the sample and the impactor at the moment when exactly this temperature is reached, it is very difficult to do due to the inertia of heating. We carried out our experiments as close to this temperature as possible. In addition, the accuracy of measuring the temperature of the samples in our experiments is plus- minus 2 degrees. And finally, the variation in the temperature of the samples in the range of 648-652 degrees C does not affect the properties of the material under study in any way. The exact temperature values of the samples in high-temperature experiments are indicated in Table 2.
In the figure caption for Figure 1, what each figure a, b, c, and d shows should be defined.
– Done, in the caption to the Figure1
In defining twin direction and size, the strange method used in the manuscript, for example, "2/8x7/94", should be explained and properly defined.
– 2-8x7-94 - means the spread of measurements over the width and length of the twins. Perhaps this designation of the spread looks a little strange, but it is repeatedly found in the scientific literature. This explanation is added to the text of the manuscript and we corrected this expression as (2-8)μm x (7-94) μm, which will probably be more understandable to readers.
"bulk module B" to "bulk modulus B". "inconel 738" to "inconel 718".
– Done
It would be good to add a new figure describing the shock-wave experiment detailing the shape of impactor and specimen.
– Shock-wave experiments performed in this work on a pneumatic gun are quite typical for such studies, a fairly complete description of these experiments is made in the manuscript, indicating the sizes of samples and impactors and other features of experimental assemblies. In an article we have just published in the same journal on the dynamic properties of the additively manufactured Inconel 718 alloy, we gave a scheme of experiments and a photo of the equipment [Andrey S. Savinykh, Gennady V. Garkushin, Sergey V. Razorenov, Svetlana A. Atroshenko, Olga G. Klimova-Korsmik and Nikita G. Kislov. Strength Properties of the Heat-Resistant Inconel 718 Superalloy Additively Manufactured by Direct Laser Deposition Method under Shock Compression. Metals, 2022, 12, 967. https://doi.org/10.3390/met12060967]. We have added a link to this article in the description of the experiments (paragraph 2.4 [17]). We couldn't do this earlier, as the article was published after we submitted this manuscript to Metals
In the discussion, only 'Hugoniot elastic limit' and 'spall strength' are discussed. However, the meaning and actual implications of those two factors are missing. Therefore, discussion on that aspect with (1) the relationship between microstructure and those two factors, (2) physical meaning of those two factors, (3) effects of those two factors on possible application, and (4) direction of improvement that should be achieved for the alloy to be used in a specific future application could be added.
– Metallographic analysis of the structure of all types of Inconel 718 alloy samples studied in this work did not allow us to do any conclusions about the relationship of the structural state of the material with its strength characteristics. To build a correlation between the structural features of the initial and heat-treated samples with their strength characteristics, it seems necessary to use electron microscopy methods for a more detailed study of the features of the internal structure. These measurements were not available during this work due to the lack of necessary equipment and experts in this field. This direction may be a continuation of this work in the near future.
– At the end of the conclusion section, we have added the following. "Thus, the measurements clearly showed that preliminary heat treatment significantly increases the dynamic strength characteristics of the Inconel 718 cast alloy, the Hugoniot elastic limit and critical fracture stresses under shock loading. In turn, these results allow us to talk about the expansion of the field of use in extreme operating conditions of products and structures made of this alloy, for example, in the aerospace industry, when the strain rates exceed 105s-1 . The obtained data on the resistance to high-rate deformation and spall fracture of the investigated Inconel 718 alloy in a wide range of load durations and elevated temperatures can be used in constructing the governing ratios and numerical modeling of the behavior of this material or specific products made of it under strong dynamic stresses".
Round 2
Reviewer 2 Report
1. The organization of the paper should be improved, such as proper arrangement of the equaitions and figures, detailed discription of shock test with figures and photos.
– In the structure of the manuscript we followed the recommendations of the editorial board as the IMRaD (Introduction, Methods, Results, and Discussion) and consider the article to follow this structure.
I don't mean the change of the sessions. It refers the arrangement of tables, equations and proper titile of figures. Such as Table 3 is arranged in the result session, it is better to clarify clearly the test schame in the experiment. For example, the calcualtion of speed in Table2 should be together with Table2. For example, the equations is better to single out from paragraph. So, the paper should be thoroughly checked and improved.
2.The shock experiment device, sample and impactor should be illustrated. The sizes of samples and impactors. and the photos of samples after shock experiment.
– Shock-wave experiments performed in this work on a pneumatic gun are quite typical for such studies, a fairly complete description of these experiments is made in the manuscript, indicating the sizes of samples and impactors and other features of experimental assemblies. In an article we have just published in the same journal on the dynamic properties of the additively manufactured Inconel 718 alloy, we gave a scheme of experiments and a photo of the equipment [Andrey S. Savinykh, Gennady V. Garkushin, Sergey V. Razorenov, Svetlana A. Atroshenko, Olga G. Klimova-Korsmik and Nikita G. Kislov. Strength Properties of the Heat-Resistant Inconel 718 Superalloy Additively Manufactured by Direct Laser Deposition Method under Shock Compression. Metals, 2022, 12, 967. https://doi.org/10.3390/met12060967]. We have added a link to this article in the description of the experiments (paragraph 2.4 [17]). We couldn't do this earlier, as the article was published after we submitted this manuscript to Metals
It is good to give the reference for the experiment conditions, but it is the most important conditions, it is better to give the illusttration and the dimensions on the diagram. Note the illustration diagram in the referecne is not clearly give the dimensions mentioned in Table 3. And the diameter of the specimen is not mentioned, it is the same as the rod?
4.The scale of x and y is not uniform in FIg. 5. The axis of Fig.7 should be clearly denoted in log scale.
– In Fig.5, the scale of the X and Y axes is really different, but this is done to maximize the use of the field of the figure. This practice is generally accepted; especially often it is done when lagorithmic coordinates are used, as in our case. In our opinion, it is clearly visible that the axes in Fig.7 have a logarithmic scale.
In fig.5, is the scale of x, y axes are nonuniform without certain rules, then how to determine the maximum value of axis which is not marked?
5.V is the current specific volume of the substance, V0 is the specific volume of the substance at zero pressure. In fact, the strain rate in our case is the rate of expansion of matter.
please discribe it in the paper.
94 µm.¸7´8¸Note some units maybe in Russian, HRD is not a unit. And expession of the thickness like 2
– HRD is not a unit of measurement, it is a commonly accepted abbreviation for Rockwell-measured hardness, which is dimensionless
For Rockwell hardness it should be HRC. The other units such as speed, thickness, stress are in Russian, please check.
6. Please clarify the difference of the this paper and the form paper mentioned as experiment condition reference.
Author Response
- I don't mean the change of the sessions. It refers the arrangement of tables, equations and proper titile of figures. Such as Table 3 is arranged in the result session, it is better to clarify clearly the test schame in the experiment. For example, the calcualtion of speed in Table2 should be together with Table2. For example, the equations is better to single out from paragraph. So, the paper should be thoroughly checked and improved.
– Table 2 moved to paragraph “2.3. Methods for calculating the characteristics of Inconel 718 alloy at 6500C”
The main content of Table 3 is the results of processing wave profiles - the strength characteristics of the material depending on the heat treatment - the main purpose of the work, and its location just after the presented wave profiles and a detailed discussion of the method of their analysis and calculation of characteristics. Regarding the loading conditions, the exact values of the thickness of the samples and impactors are only presented there, these parameters are not key when discussing the results.
We don't quite understand why it is necessary to separate calculation formulas from the text. This is a common practice when simple formulas are placed in the text with an explanation of their application. Since they are used only once in the work, their numbering is optional. We believe that moving formulas is impractical.
- It is good to give the reference for the experiment conditions, but it is the most important conditions, it is better to give the illusttration and the dimensions on the diagram. Note the illustration diagram in the referecne is not clearly give the dimensions mentioned in Table 3. And the diameter of the specimen is not mentioned, it is the same as the rod?
– The shock-wave experiments carried out in this work are typical for shock-wave measurements - this is the collision of two plates. We believe that there is no serious need to add a diagram of these simple experiments as another drawing. In the text (paragraph 2.4), the parameters of the samples (their dimensions) and the diameter of the impactor (marked in blue) have been added. In our opinion, this is enough to describe the experiments.
- In fig.5, is the scale of x, y axes are nonuniform without certain rules, then how to determine the maximum value of axis which is not marked?
– Figure 5 represents the dependence of the elastic limit of the alloy on the distance (thickness of the sample) traveled by the elastic precursor in order to understand the nature of its attenuation. The exact values of the dynamic elastic limit can be taken from Table 3. The maximum value on the Y axis does not have any special need, from the point of view of the meaning of this figure.
4.V is the current specific volume of the substance, V0 is the specific volume of the substance at zero pressure. In fact, the strain rate in our case is the rate of expansion of matter. please discribe it in the paper.
– Done, paragraph 5.1, marked in blue
- For Rockwell hardness it should be HRC.
– The essence of the Rockwell hardness measurement method is the introduction
of a diamond cone (scales A, C, D) tip into the surface of the sample.
Rockwell hardness is indicated by the symbol HR with an indication of the hardness scale, which
is preceded by a numerical hardness value of three significant digits.
In our measurements, we use the loading conditions for hardness measurements corresponding to the D scale (measurement range 40-77), so in the table we denote hardness as HRD.
The other units such as speed, thickness, stress are in Russian, please check.
– The units of measurement in Table 3 have been corrected (marked in blue in the text)
- Please clarify the difference of the this paper and the form paper mentioned as experiment condition reference.
– Additions in the text according to the reviewer's wishes are marked in blue
