Effect of Micro-Structural Dispersity of SiMo Ductile Iron on High Temperature Performance during Static Oxidation
Round 1
Reviewer 1 Report
In this article, the authors analyzed the high-temperature performance of microstructural dispersity of SiMo ductile iron during static oxidation. The work in general is interesting and appropriate for the journal. Please refer to the attached annotated PDF file for detailed comments. I have the following major suggestions for further improving the quality of presentation and a better understanding of the future readers:
- Please use SI units throughout the document. i.e kg instead of lb
- The material and method details provided on pages 3-5 are difficult to understand without appropriate context. It would be helpful if the authors can provide a flow chart of the material manufacturing, processing, and characterization to support the already given details.
- I was not able to understand that at which plane was the samples cut and what am I looking at in Fig.1 and Fig. 2
- Dimensional scales in Fig. 2 are missing for context about the size of the particles
- Figure 1 and 2 are not significantly explained, is light microscopy enough and provides adequate information about particles or CT is necessary?
- I do not understand Fig. 3. It seems to be CDF of particle sizes in different wall thickness samples. But it is written that it is a probability distribution.
- I am sure that the probability distribution plot does not look like this. Please check.
- I do not understand the data provided in Table 1 and its detail provided on Line 230-233
- In figure 6, a red curve apparently from some models is presented. The model is never discussed in the previous sections. Please check.
- Data presented in Fig. 10 is not adequate and does not provide a clear understanding of the explanation in the text. Please revise, label, and annotate this figure appropriately by showing details in magnified images for a better understanding of the readers.
- Please check axis labels of Fig. 11-a
Comments for author File: 
Comments.pdf
Author Response
R. Please use SI units throughout the document. i.e kg instead of lb
A. Done
R. The material and method details provided on pages 3-5 are difficult to understand without appropriate context. It would be helpful if the authors can provide a flow chart of the material manufacturing, processing, and characterization to support the already given details. I was not able to understand that at which plane was the samples cut and what am I looking at in Fig.1 and Fig. 2
A. The procedure to decouple oxidation and deC was adopted from our previous publication, referred in this article. We made changes in the text to clarify details of used experimental procedure.
R. Dimensional scales in Fig. 2 are missing for context about the size of the particles.
A. Fig. 2 was used for illustration of graphite particle density in approximately 1 mm3 volume or 1x1x1 mm cube. Dimensions added into Fig. 2 capture.
R. Figure 1 and 2 are not significantly explained, is light microscopy enough and provides adequate information about particles or CT is necessary?
A. Optical microcopy provide only random 2D section, while CT illustrated the real 3D structural parameters. Therefore, microCT method was used in this study.
R. I do not understand Fig. 3. It seems to be CDF of particle sizes in different wall thickness samples. But it is written that it is a probability distribution. I am sure that the probability distribution plot does not look like this. Please check.
A. All 3D diameters were measured, and statistical analysis included plotting integrated frequency curve with probability number of particle bellow or above a specific diameter. Lines in this figure indicated 0.5 probability diameter of particles. It means that half of particle number has diameter less (or larger) then shown diameter. This 3D analysis illustrated large differences in diameter distribution in studied cast irons. Explanation was added in the text.
R. I do not understand the data provided in Table 1 and its detail provided on Line 230-233. This table provided important statistical characteristics of structural dispersity.
A. The total particle number in the volume and the total interface with the matrix are two important structural parameters which will be used in discussion of oxidation and deC kinetics. Explanation was added in the text.
R. In figure 6, a red curve apparently from some models is presented. The model is never discussed in the previous sections. Please check.
A. This model was discussed in the next Discussion part “Comparison between experimentally and simulated measured depth of the deC layer and assuming a simplified diffusion model without barriers [22], shown (Fig. 6) that the simulated and experimental data fit each other only for SiMo ductile iron with fine graphite nodules at a temperature above a critical value. Changed made in Fig. 6 capture.
R. Data presented in Fig. 10 is not adequate and does not provide a clear understanding of the explanation in the text. Please revise, label, and annotate this figure appropriately by showing details in magnified images for a better understanding of the readers.
A. Explanation added in the text and labels were changed. Thank you
R. Please check axis labels of Fig. 11-a
A. Changes made in this figure. Thank you again.
Author Response File: Author Response.pdf
Reviewer 2 Report
- Mi-cro-structural dispersity is referred to as the degree of heterogeneity of sizes of structural con-stituencies within the microstructure.- correct typo errors in this sentence.
- SiMo ductile iron solidified in a casting with varying wall thicknesses from 5 mm to 100 mm. Testing of car exhaust system the required thickness should be less than 5 mm why you are chosen so high thickness, 100 mm.
- Addition-ally, the complex material behavior during oxidation-assisted transient thermo-mechanical loading will be presented in a separate article- correct typo error.
- Local formation of an oxide layer at the tip of the fatigue crack could increase the critical cycle number. Is it decrease cycle nuber, Check?
- It has been shown that when the machined surface was 86 exposed to tensile stress under fatigue, a significant increase of the endurance limit was achieved due to the elimination of surface defects [13]. Is it compressive stress? Check?
- Faster cooling castings with 18 mm and 5 mm wall thickness had significantly dispersed graphite nodule diameter when compared to slow cooling 100 mm wall thickness casting. Graphite nodules in a 100 mm wall thickness also had some number of distorted interconnected graphite particles- Describe the kintics for the change in graphite morphology.
- C-LECO analysis- expand apperivation and uniquness in measurement.
- % by oxidation gain measurement using C-LECO analysis over other methods useful for readres.
Author Response
R. Microstructural dispersity is referred to as the degree of heterogeneity of sizes of structural constituencies within the microstructure.- correct typo errors in this sentence.
A. Done
R. SiMo ductile iron solidified in a casting with varying wall thicknesses from 5 mm to 100 mm. Testing of car exhaust system the required thickness should be less than 5 mm why you are chosen so high thickness, 100 mm.
A. SiMo ductile iron also used in heavy section for furnace furniture and the other high temperature application. Also, it was important to have max possible variety of graphite dispersity.
R. Addition-ally, the complex material behavior during oxidation-assisted transient thermo-mechanical loading will be presented in a separate article- correct typo error.
A. Done
R. Local formation of an oxide layer at the tip of the fatigue crack could increase the critical cycle number. Is it decrease cycle number, Check?
A. This is correct and supported be other publications
R. It has been shown that when the machined surface was exposed to tensile stress under fatigue, a significant increase of the endurance limit was achieved due to the elimination of surface defects [13]. Is it compressive stress? Check?
A. This is correct and supported be other publications
R. Faster cooling castings with 18 mm and 5 mm wall thickness had significantly dispersed graphite nodule diameter when compared to slow cooling 100 mm wall thickness casting. Graphite nodules in a 100 mm wall thickness also had some number of distorted interconnected graphite particles- Describe the kinetics for the change in graphite morphology.
A. It is interesting suggestion. We will look at on this in future.
R. C-LECO analysis- expand apperivation and uniqueness in measurement. % by oxidation gain measurement using C-LECO analysis over other methods useful for readers.
A. Changes made in the text.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript reports the effect of the nodular density on the oxidation resistance of high-Si- and high-Mo content cast iron in air. The authors experimentally distinguish the effects due to decarburization and due to actual oxidation of the metal. The material in general appears of sufficient interest and quality for publications.
There are however, some issues, which should be sorted out prior to publication.
(1) I am helpless with the term microstructural dispersity used within the manuscript. It is apparently not widely used in the science of microstructure. A google scholar search suggests that this term could be a translation from technical terms used in Slavic languages, which are however, barely used in this way in English. During reading I tried to figure out whether dispersity simply means the (average) smallness of the size of the microstructural elements or the distribution around the average. As the crucial parameter seems to be the nodular density, I suggest to refer to the nodular density directly instead of using the unclear and unusual term dispersity. I note that at least twice dispersity became diversity....
(2) There is some quite sloppy style throughout the manuscript, which I do not regard as adequate for a scientific publication. This concerns the following points
(a) Element symbols and chemical formulas should not be in italic. The only exception might SiMo as a shorthand symbol for the type of iron. If in such a case “SiMo” would be written nonitalic, it could be misread as a chemical formula. It is also poor practice to set “Mg” equal to Mg content. Hence, in line 71 it should read Mg-to-P content ratio.
(b) There apparently a lost of lab jargon used in the text. Examples are “ductile iron chemistry” (l 110), which is actually the “composition of the ductile iron”
(c) LECO C analyses (several places). Explain the method and the instrument in line 128 and use proper technical terms at the other occurrences.
(d) Last paragraph of introduction should not be italic.
(e) l204-206: Undeleted text from the template!
(f) Table 1: the quantities n, N and S are not properly explained (a Table/Figure caption should be selfcontained!). Such an explanation is also not given in the text. Note that n and N are not numbers, but number densities. Please clearly explain your quantities, which is not done by stating the unit of the physical quantity.
(g) Figure 5 please take care of the axis label of the y axis.
(h) Please tidy up the list of references. Unique style, e.g. concerning journal abbreviation. Check incorrect text in Ref. 16
(i) What is “experimental heat” (line 144)?
(3) Add the country to the affiliations (apparently USA)
(4) Unclear text at line 251: Which different effects are “coupled”?
(5) Figure caption of Figure 6. Only at the end of the text I found a hint at Ref. [22] which explains the modeling. Such information has also to be present in the Figure caption to make it self-contained.
(6) Figure 13 and corresponding text: What is the specific nodule area ratio. This quantity has to be clearly defined. I could not really figure out whether this ratio is really dimensionless
(7) Please check the course of the sentences in the Abstract
(8) I suggest to make the Conclusions better understandable without reading the whole paper. For that purpose, fewer abbreviations should be used.
(9) l35 oxidizing instead of oxidized
(10) Section 2: How is the Si and Mo content adjusted?
(11) Please arrange a re-reading by a native speaker, but I am not willing to list the not too many but significant number of small errors.
Author Response
R. I am helpless with the term microstructural dispersity used within the manuscript. It is apparently not widely used in the science of microstructure. A google scholar search suggests that this term could be a translation from technical terms used in Slavic languages, which are however, barely used in this way in English. During reading I tried to figure out whether dispersity simply means the (average) smallness of the size of the microstructural elements or the distribution around the average. As the crucial parameter seems to be the nodular density, I suggest to refer to the nodular density directly instead of using the unclear and unusual term dispersity. I note that at least twice dispersity became diversity....
A. We agree that terminology is important in technical science. We used the term microstructural dispersity because it include multiple structural parameters related to high temperature material behavior, including graphite nodule number in the volume units, specific surface of graphite phase as well nodule diameter. Using only nodule number density is not fully characterized such structure. So, we prefer to stay with this terminology.
R. Element symbols and chemical formulas should not be in italic. The only exception might SiMo as a shorthand symbol for the type of iron. If in such a case “SiMo” would be written nonitalic, it could be misread as a chemical formula.
A.. We used italic for chemical elements to clear designate it from the text. Many chemical journals are using this stile. We left italic but if publisher will ask we will made changes.
R. It is also poor practice to set “Mg” equal to Mg content. Hence, in line 71 it should read Mg-to-P content ratio.
A. Changed made
R. There apparently a lost of lab jargon used in the text. Examples are “ductile iron chemistry” (l 110), which is actually the “composition of the ductile iron”
A. Such term used in industry. We made recommended changes in the text.
R. LECO C analyses (several places). Explain the method and the instrument in line 128 and use proper technical terms at the other occurrences.
A. Changes made in the text.
R. Last paragraph of introduction should not be italic.
A. Changes were made
R. l204-206: Undeleted text from the template!
A. Done
R. Table 1: the quantities n, N and S are not properly explained (a Table/Figure caption should be self-contained!). Such an explanation is also not given in the text. Note that n and N are not numbers, but number densities. Please clearly explain your quantities, which is not done by stating the unit of the physical quantity.
A. Done in the text
R. Figure 5 please take care of the axis label of the y axis.
A. Figure were fixed, thank you
R. Please tidy up the list of references. Unique style, e.g. concerning journal abbreviation. Check incorrect text in Ref. 16
A. Done, thank you
R. What is “experimental heat” (line 144)?
A. It is commonly used terminology in metal casting industry. It represents one batch of material made from a specific heat.
R. Add the country to the affiliations (apparently USA)
A. Done
R. Unclear text at line 251: Which different effects are “coupled”?
A. Changes made in the text
R. Figure caption of Figure 6. Only at the end of the text I found a hint at Ref. [22] which explains the modeling. Such information has also to be present in the Figure caption to make it self-contained.
A. changes made in the text
R. Figure 13 and corresponding text: What is the specific nodule area ratio. This quantity has to be clearly defined. I could not really figure out whether this ratio is really dimensionless.
A. Yes, it is relative parameters to 100 mm wall thickness. Additions made in Fig. capture.
R. Please check the course of the sentences in the Abstract.
A. Done
R. I suggest to make the Conclusions better understandable without reading the whole paper. For that purpose, fewer abbreviations should be used.
A. Changes were made in Conclusion
R. l35 oxidizing instead of oxidized
A. Changed
R. Section 2: How is the Si and Mo content adjusted?
A. Si and Mo were adjusted during melting by preliminary chemical analysis of the melt and making needed addition.
R. Please arrange a re-reading by a native speaker, but I am not willing to list the not too many but significant number of small errors.
A. Done, thank you!.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
ok now.
