Nanoindentation Investigation of Chloride-Induced Stress Corrosion Crack Propagation in an Austenitic Stainless Steel Weld

Round 1

Reviewer 1 Report

This research tried to relate the stress corrosion cracking (SCC) problem – the susceptibility and propagation – with mechanical and crystallographic behavior by nanoindentation and EBSD techniques. The motivation was clearly presented in the introduction part. The narrative and vocabulary are logical and impressive. While there are also some uncertainties when reading this work. Reviewers hope the authors can explain/revise the doubts based on the following suggestions.

1.      This paper aims to utilize nanoindentation in parallel with SEM and EBSD to determine whether nanoindentation can be used to assess the SCC susceptibility and propagation. The main confusion is that all the characterizations are done after the occurrence of chloride-induced SCC (CISCC), which emphasize the effect of crack on microstructure by nanoindentation. From the reviewer's perspective, the assessment should be described by comparing changes before and after CISCC. The elaboration should be added/adjusted in the last part of the introduction, otherwise, the object will be meaningless.

2.    What does an extra blue line in figure4(a) want to express? In addition, the meaning of the IPF diagram should be reflected in the presentation of the results.

3.    Some ambiguous sentences should be corrected.

a)    Line94:”… nanohardness of individual grains and SCC susceptibility.”

b)    Line134:” To investigate whether hardness has an effect on CISCC susceptibility…”

c)    Line157:” Based on the hardness maps, cracks are not always concentrated in solely hard or soft regions.”

4.    Figure5 needs to be reprocessed to avoid columns stacking each other. Reviewers suggested that more comparative analysis should be given in detail. For example, the normal grains/twins/GBs in crack grains can be compared in the non-crack grains, respectively. That may be possible to obtain a more convincing statement than line 137.

5.    Line163:”This behavior is consistent with previously reported observations that crystallographic hardness….” The relevant Schmid (m) and Taylor (M) factors should be derived from the EBSD data to strongly confirm the conjectural conclusion.

6.    The conclusion needs to be recondensed. The reviewer could not understand the main idea the author was trying to convey. Some constraints need to be added to make it more accurate.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

 The manuscript submitted by Qu and Wharry presents an innovative approach for the study of the SCC process in stainless steel welds.

However, the authors did not present any grain orientation relationship with the crack pattern or hardness change as a consequence of crack propagation.

The authors mentioned that in randomly-oriented polycrystalline materials, some grains experience higher shear stress, and thus undergo more plastic deformation, than neighbouring grains due to the orientation of their slip systems with respect to the applied load. In this base, please indicate the  orientation relationship between neighbouring and randomly oriented grains

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

The reviewed work Nanoindentation Investigation of Chloride-induced Stress Corrosion Crack Propagation in an Austenitic Stainless Steel Weld (metals-1809861) concerns an important area of science, namely methods of macro-scale research on the mechanical properties of the material. The presented problem concerns the issue of the formation and propagation of cracks in austenitic stainless steel weld and its identification. To this end, the authors use a number of modern research techniques, skilfully combining them with each other. Thanks to this, we obtain not only an image of the material structure, but also a description of the impact of a developing crack on the properties (hardness) of individual grains. The obtained results allow for visual visualization of the crack propagation processes known only from theory.

After reading the content of the article, my only basic recommendation is that due to the complexity of the issues presented, you need clarity and precision of expression, which in turn requires a professional linguist's correction. I also recommend making the following minor corrections:

·         It would be advisable to carry out a collective legend of all abbreviations and acronyms used in the article.

8 - … austenitic stainless steel (SS) … - whether the acronym should apply to the entire name, i.e. ASS.

9 - …crystallography underlies mechanical heterogeneities, the mechanical - crystallographic relationship… - I think this is a stylistic mistake, as it is talking about "crystalogray" as a science and not a property of a structure.

57-59 - Results will show that … - the entire sentence is a conclusion, not an assumption for the presented research.

64 and next - … into coupons with dimension… - logical error, because it is actually a plate with dimensions ... x ... and a thickness of 3 mm.

128 - The caption and Fig. 4 itself should be corrected in order to more clearly record the meaning of the symbols used. Maybe some additional legend showing individual symbols and their meaning.

141 - Numbering error, it should read: Figure 5b.

183 – Fig. 6 - Consider whether one colour cannot be used to show the crack. Add descriptions "crack", "fracture area" in the drawing ...

198 - Use the impersonal form of speech in place of the personal form (in conduct ..)

Author Response

Please see the attachment.

Author Response File: Author Response.pdf