Orientation Dependence of High Cycle Fatigue Behavior of a <111> Oriented Single-Crystal Nickel-Based Superalloy
Round 1
Reviewer 1 Report
Dear authors,
This is a very good paper with new and interesting results. My impression is that this work is a very solid piece of science and an important one.
The paper concerns the influence of crystallographic planes deviation respect to the direction of load on the strength of nickel-based single crystal superalloy. Studies have model character and are based on the high cycle fatigue in the expected operating temperature (at 800 °C). This results may be important in the aero-engine blade design process.
The essence of the article is related to the identification of dislocation mechanisms of deformation arising during fatigue tests, and based on the TEM analysis. In the research, used the number of fatigue cycles and the Schmid coefficient (shear stress) to assess the quality of the produced material. As you show, this assessment is significantly influenced by the angle of deviation of the crystallographic planes of the Ni-superalloy from the direction of the load.
However, in the article, I noticed some shortcomings that do not affect my positive opinion. My main objection is that you applied too far-reaching simplifications in it, especially in the description of the methodology of producing the alloy itself and obtaining different values of the deviation angle. It absolutely requires supplementing with appropriate descriptions and literature citations.
Use acronyms without proper explanation, e.g. SX, HRS (line 61), HCF tests (line 84). In this regard, there are some ambiguities / errors in the text, e.g. "XX scanning electron microscope (line 71).
It also seems necessary to present the methodology of fatigue tests, shapes and dimensions of samples and machine parameters of this test. There is no information about the number of these studies and their statistical study.
The article also requires a careful editorial review in terms of minor errors, e.g. sticking word groups (line 34, 36, 41, 45, 47...) or unnecessary spaces as in the notation “[ ]” (line 61, 230 and other). Please check the correctness of the symbols describing the directions or crystallographic planes in the whole text.
The statement "devasting decline ..." (line 90) seems to be too radical for such a few studies.
In line 101 and 102 there should probably be Fig. 3 and in 222 – Fig. 7.
Line 105/106 - does the statement "nickel-based SX superalloys" apply to the same material as line 61 - lack of clarity in the statement also elsewhere in the text.
The phrases "orientation A, B, C, D" used are not clear at first - please expand and clarify these phrases.
There is no defined definition of the diffraction condition parameter "g" (line 145) - please provide a clear explanation of its meaning in the text.
No explanation of what the term "types of matrix channels" (line 155) mean.
Line 207 – 208 - text layout error.
In conclusion (line 237) it would be advisable to write specifically about what Ni-alloy is mentioned in the article and its summary.
Good luck.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript presents a very interesting work on Orientation dependence of high cycle fatigue behavior of a [111] oriented single crystal nickel-based superalloy. However, to be considered for publication it has to be changed in order to make the materials and methods clearer as well as the results and their discussion clearer.
In the experimental methods, more data on how the Diagram of slip planes of fracture morphology was made should be added as well as the data referring to the schmid.Regarding the TEM data, it would be essential to add the indexed SAED results.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The current manuscript is an original study on the high-cycle fatigue performance of a [111] oriented single crystal nickel-based superalloy. The focus is put on the loading axis orientation dependence on the deformation behavior. SEM and TEM were mainly used in the analysis of fracture surface and dislocation structure in the deformation region. The major finding is that when the loading axis is deviated from [111], the fatigue life has a clear degradation. If the loading axis shifts towards [001], the deformation mechanism remains similar as the [111] case in terms of dislocation slipping; while when it shifts towards [110], stacking faults start to give a significant contribution in decreasing the fatigue life. The topic is interesting, however, the interpretation and analysis are poorly presented. I’m afraid this manuscript is not well prepared. Some points are listed below:
The fatigue testing mode used in this work is rotary bending fatigue, in contrast to conventional testing methods. The reviewer is not an expert on this loading mode, and the manuscript does not provide enough details. It is highly recommended that the authors add more information on the testing setup, testing parameters, and the stress-state.
There is no information about the fundamental mechanical properties of the studied material, e.g. yield strength. This is highly relevant to the selection of loading parameters in the test.
The interpretations should be clearly marked in the figures for better readability (e.g. the orientations/ burgers vectors of the dislocations and stacking faults that are discussed in the text), which are missing.
The maximum Schmid factor for the four orientations shows a clear relevance to the degradation of the fatigue life (higher Schmid factor -> lower fatigue life), but this was not clearly discussed in the text and all focus was put onto the individual slip system activation.
Creep has been mentioned a few times in the text, but was not discussed in details. Since the tests were performed at 800 °C, it’s highly recommended to discuss the possible creep-fatigue coupling in the deformation behavior.
A lot of cross-references are not correctly interpreted. Figure 6 appears twice in the caption. And it seems that the last figure was not interpreted in the main text.
Line 65: typo “<111><011>” and “<111><011>”
Line 71: “XX”
Line 102: “Fig.2(a)” must be wrong
Line 147-152: please correct the formatting on the bold text
Line 158: “Figure 4” must be wrong
Line 182: for orientation A in Table 1, the <112>{111} system has the highest Schmid factor. Why the shear stress was “relatively low”?
Line 185: check grammar
Line 186: a/2[110] not (110)
Line 190: check grammar
Table 1: it’s highly recommended to have additional lines to separate the four orientations. Difficult to read.
Line 217: check grammar
Line 221: “Figure 6” duplicated
Line 227-234: difficult to read. Check grammar
Line 241: “decrease along … was faster than …” This was not clearly discussed in the text, and it does not seem to provide much physical soundness to the topic.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors changed the paper according to the comments made
Author Response
Dear Referee
The detailed process and experimental data of angle relation calculation have been added to the paper and explained according to the comments of reviewers.
Thank you for your comments.
kind regards.
Bin Hu
Reviewer 3 Report
The scale of the Y-axis in Figure 2 is wrong (check ticks). And there is a weird white box on top of this figure.
Author Response
Dear Referee
The Y-axis used in Figure 2 is the logarithm.The author has tried many different types of Y-axis including linear axis in Origin software, and the drawing in the form of the logarithmic axis is the most clear and beautiful illustration. The weird white box has been readjusted due to a problem with the format conversion.
Thank you for your comments.
Kindly regards.
Bin Hu
