Round 1

Reviewer 1 Report

Please find the attached review report for better formatting

Review report

REF: Crystals-1684766

Title: Study on the Creep Behavior of Nickel-Based Single Crystal Superalloy Micro Specimens with Dimensional Effects

General comment:

This research has conducted systematically study on the creep and creep-fracture bahavior of the 2^nd generation of nickel-based single crystal superalloy with different specimen sizes subject to an elevated temperature, and the law of organization evolution was used to understand the rafting phenomena with creep of the alloy. The structure of the manuscript is clear, and the introduction is written in details. However, prior to the final decision to be made, I suggest the authors should consider addressing the following issues.

Please note all references mentioned in the comments below are for guidance only.

Major concerns:

Section 1 Introduction

The literature review is generally well written. However, there is a large section on the mechanistic understanding of the microstructure-governing micro-crack nucleation (e.g. http://doi.org/10.1016/j.ijplas.2019.10.003) and propagation (e.g. https://doi.org/10.1016/j.jmps.2021.104663 ) in nickel-based alloys, which would facilitate delivering the following holes and cracks (Figure 8).

Section 2 Experiments

Figure 1:

what are the white regions? Would they refer to unindexed  region or just impurities or non-metallic inclusions? The latter are shown to be very important in facture (http://doi.org/10.1007/s11661-018-4780-3 ).

Any methodology to indicate the crystal orientation of the \gamma phase as the crystal orientation would be significantly important for the creep rate at elevated temperature?

Section 3 Results

The mechanistic understanding  on the size-dependent creep is not sufficiently through, at least from the microstructure view. The terminology size effect could refer to many aspects: sample size (http://doi.org/10.1126/science.1098993 ), grain size (http://doi.org/10.1088/0965-0393/14/3/005 ), contact size (http://doi.org/10.1021/acsami.0c19736 ) and microstructure characteristic length (http://10.1016/j.ijplas.2020.102904 ) etc. The sample size in the manuscript is at the scale of millimetre, and hence the mechanisms should be scaled down to microstructural scale. For instance, the indentation size effect is attributed to the geometrically necessary dislocations that are shown in dislocation scale.

Figure 7 implies the microstructure morphology and size would be the key to dominate the size-dependent creep behaviour. Hence it should be discussed in details.  

Minor concerns:

Line 93: This experimental method outlined in this paper is common

This sentence sounds the authors did not use a novel method, which could be improved such that the audience would be more interested.

Figure 2-5 could be combined to make the manuscript more concise and compact.

All scale bars should be made (probably larger or stronger contrast ) more visible.

Suggestion:

Major revision

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Some questions and comments to authors,

1. Can the authors provide the EDS composition result and XRD pattern of the Ni-based superalloy to prove its structure property?
2.  Each item (A_i to C_i) in Table 2 needs to describe in the revised manuscript.
3. The brief result should be added to the Abstract.
4.  The size effect of the Ni-based superalloy is investigated in this work. The authors can provide useful suggestions for the industry?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed all the concerns in the last round of reviewing, and hence the current version is recommoned to publish in Crystals. 

Reviewer 2 Report

No more comments.