Microstructure and Properties of Fe-Based Alloy Coating on Gray Cast Iron Fabricated Using Induction Cladding

Round 1

Reviewer 1 Report

The subject/title of this manuscript, “Microstructure and properties of Fe-based alloy coating on gray cast iron fabricated using induction cladding”, is interesting and fits well within the scope of Coatings. However, in its current state it contains several limitations and more work is necessary!

GENERAL COMMENTS:

The level of English does not meet the journal's desired standard!  It is vital for the authors to get a fluent English speaker to check and correct their manuscript!

The manuscript appears to be written in a hurry, there are lots of mistakes which could have easily been avoided. There are numerous examples, where the authors include gaps in wrong places, no gaps, etc. Also, it is recommended to always include gaps between numbers and units.

Selected examples:

• Line 75: Change from “…(sample Fe-1)and…” to “…(sample Fe-1) and…”
• Line 76: Change from “…and Fe-3).A…” to “…and Fe-3). A…”
• Line 97: Change “…machine(EDM)…” to “…machine (EDM)…”
• Line 127: Change “…625m, 1250m, 1875m and 2500m…” to “…625 m, 1250 m, 1875 m and 2500 m…”

1. INTRODUCTION:

• Only eleven (11) references are included in this section. A more detailed review of the available literature is required, more references to be added.
• Line 28: PVD stands for “Physical Vapor Deposition”, not for “vapor phase deposition”.
• Line 47: The sentence “The results reveal that” is not complete, parts are missing.  

2. EXPERIMENTAL PROCEDURES: The authors describe the induction cladding experiment procedure (e.g. Fig. 1), how they prepare the three coatings.    

• Line 103: Why was a load of 200 g selected?
• Line 124: “Based on the previous study…”. Include references here. 

3. RESULTS AND DISCUSSION: Only two references (refs. [12] and [13]) are included in this section. A more detailed discussion is needed!

Additional (selected) points:

• The authors first describe all three coatings in section “3.1. Forming mechanism of Fe-based coating”, before they focus on sample Fe-3.
• Line 140: A better image is needed in Figure 4 (a), plus a scale bar should be included.
• Line 155-156: “As a results, the melting process cannot conduct smoothly”. Rephrase this sentence. It is not clear.
• Line 157: “…which is not benefit for the alloy powder, melting sufficiently…”. Rephrase, improve English.
• Line 170, Figure 5: Increase scale bars/font sizes in the images on the right side.
• Line 182, Figure 7: Increase scale bars and font sizes on axes.
• Line 184, Figure 8: use cycles, dashed lines… to better show the areas ib the images.
• Line 197: “…765 HV0.1…”stated, but 200 g mention in experimental section. Please clarify.
• Line 212, Figure 10: Increase font sizes of text in figure.
• Line 226, Table 3: Include gaps; i.e. change to “Ecorr (V)”
• Line 234, Table 4: Arrange text, gaps…
• Line 259, Figure 13: Included gaps between the number and units; i.e. change to “2 μm”.
• Line 282, Figure 14: Better to remove cures fittings?

The authors carefully need to address the above mentioned points, include more references in the manuscript, especially in the introduction, strengthen the discussion, improve the English, the figures… In its current state, the reviewer has no option but to reject the manuscript. Very major revision is required. 

Author Response

 The wording and formating mistakes in the whole paper have been checked and revised.

2. EXPERIMENTAL PROCEDURES: The authors describe the induction cladding experiment procedure (e.g. Fig. 1), how they prepare the three coatings.    

• Line 103: Why was a load of 200 g selected?

Under the most of experimental and practical conditions, relative higher load can reduce the fluctuation of hardness value and generate larger and clearly visible indentation. Moreover, according to some references, a load of 200 g is often used to measure the Fe-based alloy coating.

• Line 124: “Based on the previous study…”. Include references here. 

 Here we mean “according to our previous experimental results”, and the relevant clarification was make in Line 125.

2.RESULTS AND DISCUSSION: Only two references (refs. [12] and [13]) are included in this section. A more detailed discussion is needed!

Some more references was added in section 3 to provide more detailed evidence and proof.

Author Response File: Author Response.docx

Reviewer 2 Report

The article discusses the properties of Fe-based alloy coating on gray cast iron fabricated using induction cladding. The article contains a number of interesting results, but requires significant improvement - both in terms of eliminating numerous typos and inaccuracies, and in terms of the design of experiments.

A key issue that significantly affects the overall design of the study is that at the beginning three types of coatings are considered: FE-1 Fe-2 Fe-3, but then only one type (Fe-3?) Is considered - and where did the FE- 1 and Fe-2? And how to understand that it is Fe-3 that is being considered? (This is indicated only in line 173 loya of Fig. 6, but not indicated in Fig. 6 itself and in the following text and in the figures. This significantly confuses the reader. If only Fe-3 is considered, then why do we need FE-1 and Fe -2?

Line 28: It is still more correct to label PVD as "Physical vapor deposition" (instead of "vapor phase deposition").

Line 47 - The phrase is incomplete.

Lines 57-59: There is no point in giving a summary at the end of the introduction. It is more correct to end the Introduction with the formulation of the goals and objectives of the study.

In my opinion, there are many unnecessary details in Fig. 3 that distract attention from the main thing (for example, a servo motor with buttons, mounting screws, springs, etc.) - I recommend leaving only elements that explain the movement kinematics and key elements of the measurement scheme. for example, if bias springs are important in the circuit, they should be labeled accordingly. The same applies to all key (significant) elements.

Line 124 "Based on the previous study ..." - you must indicate the appropriate references.

You need to add a scale bar in Fig. 4a

In general, in FIG. 4 poor image contrast, I recommend increasing the contrast so the images are clear.

It is also desirable to give some fragments with a large scale of the image, since now, for example, filler, are hardly distinguishable. In general, the images in FIG. 4. poorly and insufficiently described. Large-scale research would also improve the depth of process research.

FIG. 5 - Line 171 is the wrong font size.

FIG. 5 - "Fe-based coating" - what is it? FE-1 or Fe-2 or Fe-3? If the authors have introduced a designation for coatings, it is necessary to use these designations. What is (a) and (b)?

The same applies to the text below. As I understand it, the authors investigate further only the Fe-3 coating. But they do not denote it, simply calling it "coating", but since the three coatings were considered above, it is difficult for the reader to understand what exactly is being investigated. Why are there no similar studies for Fe-1 and Fe-2?

FIG. 8 - how did the authors understand that the presented objects are "graphite", "cementite" or Fe3C? To do this, it is necessary to carry out a phase analysis or, at least, to examine these areas at significantly higher magnification (preferably using TEM).

FIG. 12 - the caption does not match the image. If an experimental design is considered, this should be moved to the Experiment procedures section.

FIG. 13 - transcript (c) (b), etc. should be in the caption.

FIG. 13. How did the authors understand that the image is a "corrosion product"? There must be an elemental / phase composition. How do the authors distinguish between α- (Fe, Cr), Fe3C and (Cr, Fe) 7Cr3 only in appearance?

FIG. 16. What is Spectrum 3? Where can the reader see this data?

FIG. 16. It is advisable to mark (for example, a dotted colored rectangle) area (c) in image (b).

FIG. 16 (a) - how can one understand that there is "plastic deformation" - at this scale of the image, I do not see it.

The article contains many typos, format violations. The English language needs additional improvement (I recommend professional proofreading).

Author Response

A key issue that significantly affects the overall design of the study is that at the beginning three types of coatings are considered: FE-1 Fe-2 Fe-3, but then only one type (Fe-3?) Is considered - and where did the FE- 1 and Fe-2? And how to understand that it is Fe-3 that is being considered? (This is indicated only in line 173 loya of Fig. 6, but not indicated in Fig. 6 itself and in the following text and in the figures. This significantly confuses the reader. If only Fe-3 is considered, then why do we need FE-1 and Fe -2?

Due to the high carbon content in both Fe-based coating and matrix materials, it is extremely difficult to control the cladding process and the coating quality. Based on the research of other cladding techniques, it is found that welding flux and heat treatment can effectively improve the quality of cladding coating. Inspired by those outcomes, we intended to apply the similar approaches to improve the Fe-based alloy coating. In this work, sample Fe-1 and Fe-2 are employed to study the effect of the welding flux and prolonged heating time, respectively. From Fig.4, it can be observed that only sample Fe-3 which is added welding flux and treated by prolonged heating time has a high quality coating. Therefore the following analysis is all carried out on sample Fe-3, and the related clarification is supplied in line 178 to 180.

Line 28: It is still more correct to label PVD as "Physical vapor deposition" (instead of "vapor phase deposition").

Line 47 - The phrase is incomplete.

Lines 57-59: There is no point in giving a summary at the end of the introduction. It is more correct to end the Introduction with the formulation of the goals and objectives of the study.

In my opinion, there are many unnecessary details in Fig. 3 that distract attention from the main thing (for example, a servo motor with buttons, mounting screws, springs, etc.) - I recommend leaving only elements that explain the movement kinematics and key elements of the measurement scheme. for example, if bias springs are important in the circuit, they should be labeled accordingly. The same applies to all key (significant) elements.

Line 124 "Based on the previous study ..." - you must indicate the appropriate references.

You need to add a scale bar in Fig. 4a

In general, in FIG. 4 poor image contrast, I recommend increasing the contrast so the images are clear.

It is also desirable to give some fragments with a large scale of the image, since now, for example, filler, are hardly distinguishable. In general, the images in FIG. 4. poorly and insufficiently described. Large-scale research would also improve the depth of process research.

FIG. 5 - Line 171 is the wrong font size.

FIG. 5 - "Fe-based coating" - what is it? FE-1 or Fe-2 or Fe-3? If the authors have introduced a designation for coatings, it is necessary to use these designations. What is (a) and (b)?

The same applies to the text below. As I understand it, the authors investigate further only the Fe-3 coating. But they do not denote it, simply calling it "coating", but since the three coatings were considered above, it is difficult for the reader to understand what exactly is being investigated. Why are there no similar studies for Fe-1 and Fe-2?

Based on our present experimental results, only adding welding flux and pronged heating time can make good quality Fe-based coating. Therefore, from section 3.2 and following study, only sample Fe-3 was focused on. And the relevant clarification is given in line 178 to 180.

FIG. 8 - how did the authors understand that the presented objects are "graphite", "cementite" or Fe3C? To do this, it is necessary to carry out a phase analysis or, at least, to examine these areas at significantly higher magnification (preferably using TEM).

According to the reference, we found that the microstructure in the interface of induction cladding Fe-based coating is similar to that of laser cladding coating. The related explanation and references are given in line 202. Microstructure in the interface zone significantly affects the bonding strength, we will carry out further study in more details.  

FIG. 12 - the caption does not match the image. If an experimental design is considered, this should be moved to the Experiment procedures section.

Fig. 12 illustrating the equivalent circuit diagram is derived from Fig. 11, used to fitting the parameters of Nyquist diagram.

FIG. 13 - transcript (c) (b), etc. should be in the caption.

FIG. 13. How did the authors understand that the image is a "corrosion product"? There must be an elemental / phase composition. How do the authors distinguish between α- (Fe, Cr), Fe3C and (Cr, Fe) 7Cr3 only in appearance?

Combining the EDS and XRD results, the microstructure of coating could be identified. In the corroded surface analysis, only elemental composition analysis was conducted. But according to the research on the Fe-based alloy coating with similar chemical composition, the composition of corrosion product can be inferred.  

FIG. 16. What is Spectrum 3? Where can the reader see this data?

FIG. 16. It is advisable to mark (for example, a dotted colored rectangle) area (c) in image (b).

FIG. 16 (a) - how can one understand that there is "plastic deformation" - at this scale of the image, I do not see it.

The marks and labels in Fig. 16 were changed.  

Author Response File: Author Response.docx

Reviewer 3 Report

In complex tribological contacts between cylinder liner and the piston of motors and pumps there is always an intensified wear process, due to the existing poor lubrication conditions.

Improving the wear resistance of cylinder liner (usually made of cast iron) is an actual research issue. Coatings applied on the inner surface of the cylinder (liner) can realize this.

In the analyzed paper, coating of Fe-based alloy was deposited by induction cladding on base samples of grey cast iron. A special technique was applied, by using of welding flux and prolonged heating time, in such way obtaining better quality coatings.

The quality of the coating was studied from the viewpoint of microstructure by optical microscopy and scanning electron microscopy (SEM). In addition, corrosion resistance in NaCl solution, micro hardness, and wear resistance of the coating were investigated by tests on electrochemical workstation CHI604E, Vickers microhardness tester (HX-200), and self-made reciprocating sliding tribometer, respectively. The elemental and phase composition of the coating were revealed by energy dispersive spectrometer (EDS) and a X-ray diffractometer (XRD).

Even if the authors previously applied this method to Ni-based alloy coating [7], the originality of the paper comes from the improved induction cladding method of Fe-based alloy on grey cast iron under welding flux and prolonged heating time.

Nevertheless, the scientific value of the paper can still be improved by answers to some questions and suggestions.

1.      The equipment for microstructure and elemental and phase composition analysis is not specified (type and manufacturer).

2.      How many samples were tested on tribometer? If there was only one coated sample tested, the cleaning of the sample with alcohol at each 625 m of sliding distance, followed by necessary wear measurements by dismounting and mounting of the sample in the clamping device of the machine, may affect the results of friction and wear tests.

3.      In the caption of Figure 13 and in following discussions it is not specified what (a), (b), (c), and (d) images represent.

4.      “Wear distance” is in fact “sliding distance”, as it is not obligatory to have important wear when sliding (line 271 and 274).

5.      Line 275: “to be stabler and lower” can be replaced by “to stabilize at lower values”.

6.      In Figure 16, the morphology of worn sample made of base material should be also presented and discussed.

Author Response

 The equipment for microstructure and elemental and phase composition analysis is not specified (type and manufacturer).

The type and manufacturer of SEM and XRD has been listed in line 101 and 105 respectively, as follows:

An optical microscope(OM, GX51, OLYMPUS) and a Supra 55 Sapphire scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) are employed to observe the microstructure and elementary distribution at the cross section of the coating respectively. The phase composition of the coating is examined by a X-ray diffractometer (XRD, PANalytical-Empyrean).

      How many samples were tested on tribometer? If there was only one coated sample tested, the cleaning of the sample with alcohol at each 625 m of sliding distance, followed by necessary wear measurements by dismounting and mounting of the sample in the clamping device of the machine, may affect the results of friction and wear tests.

We used different coating samples to conduct tribological test in this work, varying sliding distance between 625 m and 2500 m. However, due to the subtle microstructure differences and phase composition in the coating could induce different wear behavior, the influence of coating sample should be further analyzed in our following study.    

3. In the caption of Figure 13 and in following discussions it is not specified what (a), (b), (c), and (d) images represent.

Fig. 13(a) and (c) represent the corroded surface of coating, (b) and (c) refer to substrate. The revision was made in the caption of Fig. 13.

4. “Wear distance” is in fact “sliding distance”, as it is not obligatory to have important wear when sliding (line 271 and 274).

Sliding distance is a more exact and accurate terminology, and wear distance was replaced in the whole text.

      Line 275: “to be stabler and lower” can be replaced by “to stabilize at lower values”.

The words has been revised according to the review’s recommendation.

 In Figure 16, the morphology of worn sample made of base material should be also presented and discussed.

The morphology of the worn surface and wear mechanism analysis of substrate were added.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Although the authors have carried out some changes, more work is necessary to bring this manuscript in a publishable shape. The authors failed to address all the problems identified in their original manuscript, have also not properly responded to the points raised by the reviewer (they only responded to a few points).

ENGLISH:  The level of English does still NOT meet the journal's desired standard!  A few sentences were corrected, but unfortunately some more mistakes were introduced in the revised manuscript.  It is vital for the authors to get a fluent English speaker to check and correct their manuscript!

Selected examples form the first page:

- Lines 8-17:  Abstract: Gray cast iron is widely used for the cylinder bores of marine diesel engines. With the aAim to improve the properties of the cylinder liner and maintain the matching ability with the piston ring under the harsh working conditions, the Fe-based alloy coating is fabricated onto the gray cast iron using induction cladding. Owing to the high carbon content in both the coating and the substrate materials, it is extremely difficult to control the coating process and the coating quality. The additive addition of welding flux and prolonged heating time is proposed to prepare a good quality coating. The coating forming mechanism is investigated, and the electrochemical corrosion and tribological properties of the coating are examined. The results show that the Fe-based coating possesses better corrosive and tribological performance than gray cast iron, and it is seemsed to be a potential candidate for improving the performance of the cylinder liners.

-Lines 20-31: 1. Introduction

With the development of the marine diesel engine, the critical working parameters of the engine are dramatically intensified, such as higher power, higher combustion efficiency, lower fuel consumption, lower emission and longer service life. The cCylinder liner is a key component influencing the durability of an engine, and accordingly its corrosion resistance and wear performance need to be further improved. The use of sSurface coating techniques is not only a highly effective approach to improve the surface performance, combining with choosing various coating materials and designing flexible coating structures, but also provides a potential option to reduce fuel consumption and emissions[1]. Widely used surface coating techniques include electroplating[2], physical vapor deposition (PVD)[3], thermal spraying[4] and cladding, in which laser cladding and induction cladding have the great potential to fabricate coatings overwith large areas withand controllable thickness and good metallurgically bonding towith the substrate.

These are just some suggested changes for the first lines. However, changes are also required to the rest of the manuscript!  Nearly every sentence/paragraph contains spelling… errors.  

Additional references were included in the introduction, strengthening this section.

Additional references were also included in the results and discussion section, a more detailed discussion was provided and the figures were improved. However, Tables 2+4 should be improved (i.e. have units in one line and in brackets…).

It is suggested to start the “3.1. Forming mechanism of Fe-based coating” with a text, before displaying Figure 4.

Change in the conclusions section “…by the additive of welding flux…” to “…through the addition of welding flux…”.

The authors really need to improve the English throughout their manuscript! The level of English does still NOT meet the journal's desired standard! 

Reviewer 3 Report

All the requested tasks were accomplished.