Study of PVD-Coated Inserts’ Lifetime in High-Pressure Die Casting Regarding the Requirements for Surface Quality of Castings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study unfolds a comprehensive investigation into the lifetime of PVD nitride coatings under HPDC process. It was found that the TiN coating exhibited longer lifetime comparing to other nitride coatings. In addition, the failure mode was also detailed investigated. I am pleased to recommend this manuscript for publication in Coatings. However, some issues are suggested to be addressed to augment the manuscript's lucidity and scholarly robustness:

1.     In the abstract, the abbreviation SEM only appeared once. There is no need to define this abbreviation in the abstract.

2.     In the introduction, the abbreviation HPDC should be defined appeared in the main-text for the first time.

3.     Why TiN, TiAlN, CrAlSiN coatings were compared in this study? The composition of these coatings has huge difference. What is the purpose to compare these coatings in this study? Please clarify in the Materials and Method section.

4.     Multilayer structures have been designed to improve the performance of PVD coatings, which is suggested to be mentioned in the Introduction section. Some review articles can be referred (https://doi.org/10.3390/nano12091388; https://doi.org/10.1007/s40544-017-0181-7)

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

This research is interesting. I have some comments as follows:

1. Since the title of this work was about "the inserts' lifetime", how did you use surface roughness as a measure for the lifetime? Please clarify and give some papers using other measures for the inserts' lifetime.

2. Once again, since the the work title was about "the quality of castings", how did you use surface roughness as a quality characteristic for the quality of the castings? Please clarify and give some papers using other measures for the quality of the castings.

3. It might be better if you should some arrow signs to point the defects (e.g., crater) on the surface morphology in Figure 4.

4. In Figure 5, you might point the local erosion using some arrow signs on the SEM image.

5. In line 227, please provide more detailed descriptions how you specified the tolerance limit of 2.5 microns for the life time of the inserts.

6. In Figure 6(a)-(c), why did you perform polishing for uncoated insert with different Ra values for other inserts? Please give more detailed explanations.

7. In Figure 6(d), why did not you perform polishing for TiN? Please clarify.

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

The authors have conducted an interesting study of PVD coated inserts’ lifetime in high-pressure die-casting regarding the requirements for quality of castings. A large amount of experimental work has been done, however, the manuscript needs some revisions:

·         Abstract needs improvement. Please add specific results, for example, on the resulting roughness/hardness obtained after the deposition of the nitride coatings;

·         Please add in the „Materials and Methods” section which exact PVD-method (vacuum deposition, sputter deposition, arc vapor deposition, ion plating, etc.) the coatings you mentioned were deposited and under what technological conditions. The technological conditions during the deposition of such coatings significantly influence the resulting properties, such as roughness and hardness;

·         Please add under what conditions the plasma nitriding was done and how the thickness of the nitride layer was measured (lines 112-113);

·         Please add how the thickness of the TiN, TiAlN, and CrAlSiN coatings was measured (line 121);

·         Please specify which inserts are mechanically polished (lines 159-161), as Figure 6 indicates that this procedure was applied to all inserts except the titanium nitride-coated insert.

·         Please improve the quality of Figure 3 if possible, and swap figure caption 3a with 3c;

·         Please add optical and SEM analyzes (Figure 3 and Figure 4) of an uncoated insert (AISI H11) to see what the difference is after deposition of nitride coatings (TiN, TiAlN, and CrAlSiN); there is also a lack of data on the microstructure of the inserts with deposited coatings from TiAlN and CrAlSiN. Please add these results.

·         How did you determine the exact phase/chemical composition of the coatings you obtained? It may be reasonable to add results from X-ray analysis and/or energy-dispersive X-ray microanalysis.

·         Please add SEM images of the cross-section of insert samples coated with TiAlN and CrAlSiN after shots.

·         Please add the standard deviations of the hardness and roughness values to Table 3;

·         Please specify the thickness of the titanium nitride coating. In Line 121 says "around 2 μm" and line 196 - "around 1.25 μm".

·         Please align the values ​​along the abscissa axis in Figure 6 (shot number 7000, 10500, 12000, or 15000).

·         Please improve the discussion. The relationship between the technological conditions of deposition of the nitride coatings and the resulting structure and properties (hardness and roughness) should be clarified.

In conclusion, the presented work has significant scientific value and should be published, however, only after the same major revisions are performed.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have greatly improved the quality of the manuscript. The manuscript can be accepted for publication.