Alternatives to Reduce Hot Cracking Susceptibility of IN718 Casting Alloy Laser Beam Welds with a Mushroom Shape

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thorough review reports often follow this structure:
• Consider starting with a short summary of the manuscript explaining what the study is about.

This research paper is devoted to the weldability and hot cracking susceptibility in laser beam welds of precipitation-strengthened Ni-based 718 alloys (wrought and with tailored chemical composition). The cracking susceptibility of test material was examined through the application of both continuous and pulsed laser beam welding. Non-destructive tests were used to study the influence of welding parameters, chemical composition of workpiece material, and pre- and post-welding treatments on both internal and external cracks. Abstract section describes briefly the main methods and treatments applied. Main findings and conclusions were indicated in this part of this article. The list of keywords is specific to the article. The Introduction section presents the importance of welding in manufacturing of turbine blades, problems related to hot cracking during welding and the impact of individual chemical elements on cracking and strengthening behavior of Ni-based alloys. In this section, the advantages of laser beam welding compared to arc welding methods are presented in a very limited way. The last paragraph of the Introduction section discusses the content of this paper. The beginning of the 'Materials' subsection presents the methods of treatment of the different Ni-based 718 alloys. Table 1 presents the detailed chemical composition of the materials tested. The chemical composition is supplemented by fractional analysis of phases. Bead on plate welding procedure and process parameters are discussed in subsection 'Welding process LBW'. Cracks resulting from the welding process were identified using Fluorescent Penetrant Inspection testing, inductive thermography and X-raty inspection which has been explained in subsection 2.3. Inductive Thermography tests were carried out using Flir X6541sc refrigerated camera and custom quadratic inductor designed at LORTEK. An Eresco X-ray emission equipment with maximum voltage of 200 kV and amperage of 4.5 mA was also used for weld inspection. Scanning electron microscope (Zeiss Ultra Plus) and both stereoscopic and conventional optical microscopes were used in metallographic characterization. The results of the analysis of carbides and Laves phases are included in section 3.1. Section 3.2 containing selected welding parameters should be classified as Methods, not Results. Comparison of defects detected using three non-destructive techniques and a brief discussion of the results is the subject of subsection 3.3. The metallographic analysis based on the micrographs of cross-sectional areas of weld beads is included in the Section 3.4. The first five paragraphs in the Discussion section repeat the information found in the Results section. The discussion section also includes one subsection with alternatives to reduce hot cracking. It is not correct to create only one subsection in the main section. The work is concluded by the Conclusions section. The conclusions in this section are consistent with the evidence presented. The list of references supporting this manuscript contains 39 items. The topics cited are consistent with the topic of this manuscript. It is difficult to assess whether the references are up-to-date because some of them do not have full information regarding the date of publication. This list has been formatted very carelessly, contrary to the instructions for authors.

• Then, explain each of the issues found that need to be addressed. Divide
the list into major issues and minor issues.

Major issues
1. First of all, the references in this article are incorrect and marked 'Error! Reference source not found'. Due to the negligence of the authors, it is impossible to assess the merits of this article. Another review round after potential revision is necessary.```
2. In the Materials section it was specified that the test plates had a thickness of 2.5, 5 and 10 mm. The question arises what does 3 mm in Table 7 mean.
3.  Discussion (lines 402-421) duplicates the findings of the Results section. The discussion is not well-integrated with the results. There is no discussion of the results here, only the conclusions. Therefore, this section should either be rewritten or deleted. If the authors wish to leave it, the discussion should be enhanced by comparing your findings with those of other researchers in the field, providing a coherent narrative of the study's outcomes.
Minor issues
1. Type lines 125: I do not agree that 'The chemical composition of the Aref alloy was according to UNE EN 10302:2010 128 standard. According to the requirement of this standard Mn = 0.35 wt.%, Cu = 0.30 wt.% and according to the chemical composition of the tested alloy (Table 1) Cu = 0.016 wt.% and Mn < 0.050 wt.%. Furthermore, what does the asterisk at Ni in Table 2 mean?
2. Please update the Introduction section with up-to-date references to provide readers with the most current knowledge. Especially a review of publications from the last 5 years is desirable (https://www.mdpi.com/reviewers).
3. When presenting the results, there is a lack of comparison with results from current literature. This will improve the reader's understanding of the contribution of your paper to the existing knowledge.

• Major issues might include problems with the study’s methodology,  techniques, analyses, missing controls or other serious flaws.

1.    Why was the mass fraction of phases in test alloys simulated by Thermo-Calc v2020b? The experimental phase analysis shows more reliable results.
2.    The authors used different treatments of samples (type lines 181-184). However, the laser welding parameters were constant for all experiments. How was it determined that for all sample treatments the welding parameters (Table 4) are optimal?
3.    No information on repeatability was provided. However, the interpretation of the results indicates that only one experiment was performed for each type of sample. The welding process, as is commonly known, is burdened with a scatter of results, especially in the area of defects formed in the weld. At least three experiments should be performed to obtain statistically reliable results.

• Minor issues might include tables or figures that are difficult to read,  parts that need more explanation, and suggestions to delete unnecessary text.

Figures and are clear and do not require changes.
Parts that need more explanation:
(a) The term welding method in the title and abstract is misleading. The welding process used in this article should be referred to as laser bead on plate welding.
(b) All symbols in Figure 1 must be explained or defined for readers who may not be experts in the field.
(c) Figure captions 5-10 should be improved. Effective captions typically include a declarative title of what you are presenting in the figure. According to, for example, the caption of figure 5 (Reference Sample Aref, Circular 2 continuous LBW) it is not clear what is in this figure.

Suggestions to delete unnecessary text:
The paragraph (lines 484-488) should be moved to the end of the Introduction section.

Author Response

Please see the attachment

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. In general, cast alloys are rarely considered for welding due to their unidirectional microstructure, which is susceptible to hot cracking. What are the potential applications of this alloy, and what is the necessity of welding it?

2. Please review the citation of the tables in the text as there appear to be some errors.

3. The details of the welding and the welding parameters are unclear and need improvement.

4. According to Figure 3, were the tests conducted according to standard procedures, or how was the circle diameter determined?

5. Based on the chemical composition, it was expected that A1 and A would have more precipitates than Aref due to their higher Al and Ti content. What is the mechanism that leads to more precipitates forming in Aref compared to the others?

6. Please provide images of cracks in the heat-affected zone (HAZ) or welds and explain how they were minimized.

7. Did the present study conduct any experiments to optimize the welding conditions? The given welding conditions may not be optimal.

8. Generally, heat treatment processes enhance precipitates in the alloy. What was the key reason for using Hot Isostatic Pressing (HIP) in this study? Please provide proper evidence for this choice.

Comments on the Quality of English Language

minor

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have incorporated the given comments and suggestions into this revised manuscript. They added the pdf document containing point-by-point responses. Their answers are satisfactory. The manuscript is now in a good shape and can be accepted in its present form.

Reviewer 2 Report

Comments and Suggestions for Authors

I appreciated the author's efforts in the revision to enhance its quality.

Please provide the suggested results for the final manuscript.

1. In the case of circular welds., a clear view of the macrograph at the overlapping zone needs to be provided to the final manuscript. 

 

Comments on the Quality of English Language

minor