Combined Effect of Substrate Temperature and Sputtering Power on Phase Evolution and Mechanical Properties of Ta Hard Coatings
Round 1
Reviewer 1 Report
Thank the authors for submitting this paper to Metals journal. The topic is exciting and worthy of investigation. So, it deserves publication after a minor revision.
Comment (1): the term “structural evolution” is ambiguous in the title of the manuscript. I wondered if the authors meant “microstructural evolution”. The title must be revised.
Comment (2): Please add supporting references to this statement: “The effects of substrate temperature or sputtering power on the preparation of Ta coatings have been investigated separately.”
Comment (3): What do you mean by “structural evolution” in the following statement? Please rewrite the sentence further: “however, their combined effect on the structural evolution and mechanical property of Ta hard coatings has not been reported yet.”
Comment (4): Please specify the technique utilized for determining the chemical composition of the substrate in Table 1.
Comment (5): In Table 1, the carbon concentration was reported with three decimals places of accuracy. I wondered what technique was utilized for measuring the carbon concentration.
Comment (6): In Fig 2a, b, and c, report the JCPDS file numbers. Graphically add the standard diffraction lines of the identified phase(s) to the XRD patterns to illustrate the phase matching and verify the phase identification results.
Comment (7): Please report the penetration depth of the x-ray beam in the XRD analysis technique.
Comment (8): Please report the accuracy of the texture coefficient values.
Comment (9): What software package was utilized? “The size distribution histograms were obtained by measuring more than 100 grains from the FESEM images.”
Comment (10): in the following statement, please cite the relavant literature: “Compared with the studies in other literatures, the Ta coating prepared in this work has good adhesion as well as strong resistance to cracking”
Author Response
Point 1: the term “structural evolution” is ambiguous in the title of the manuscript. I wondered if the authors meant “microstructural evolution”. The title must be revised.
Response 1: We thank the reviewer for raising this question. In our research, the phase structure can be regulated by combined effect of substrate temperature and sputtering power. So, the term “structural evolution” means “phase evolution”. We have revised the title.
Point 2: Please add supporting references to this statement: “The effects of substrate temperature or sputtering power on the preparation of Ta coatings have been investigated separately.”
Response 2: We appreciate the reviewer for this kind recommendation. According to your suggestion, we have added relevant references in the revised manuscript, which can be seen in Page 2.
Point 3: What do you mean by “structural evolution” in the following statement? Please rewrite the sentence further: “however, their combined effect on the structural evolution and mechanical property of Ta hard coatings has not been reported yet.”
Response 3: We thank the reviewer for raising this question. The term “structural evolution” means “phase evolution”. And We have re-wrote the sentence in the revised manuscript as the following: however, their combined effect on the growth and phase evolution of Ta hard coatings has not been reported yet.
Point 4: Please specify the technique utilized for determining the chemical composition of the substrate in Table 1.
Response 4: We thank the reviewer for raising this question. But we are so sorry that the chemical composition of the steel substrates was not tested by us. The steel substrates were bought in Fushun Special Steel Co., Ltd., China. They did the test according to the national standards, and gave us the test report when the steels left the factory. The test report contained the compositions and contents of various elements. This test report was valid and reliable.
Point 5: In Table 1, the carbon concentration was reported with three decimals places of accuracy. I wondered what technique was utilized for measuring the carbon concentration.
Response 5: We thank the reviewer for raising this question. We want to express our regret again to the case that the chemical composition of the steel substrates was not tested by us.
Point 6: In Fig 2a, b, and c, report the JCPDS file numbers. Graphically add the standard diffraction lines of the identified phase(s) to the XRD patterns to illustrate the phase matching and verify the phase identification results.
Response 6: We are grateful for the suggestion. According to your suggestion, we have added the standard diffraction lines of the identified phases in Page 6.
Point 7: Please report the penetration depth of the x-ray beam in the XRD analysis technique.
Response 7: We thank the reviewer for this kind suggestion. The specific penetration depth of X-ray is based on the incident angle and material parameters [1]. The penetration depth of the X-rays can be expressed as , The t0 is the sample thickness through which the X-ray decayed from initial intensity to e-1, µm is the mass absorption coefficient of the material and ρ is the density of the material. In our research, XRD patterns of Ta coatings all exhibit substrate peaks with different intensities. This indicates that the penetration depth of the X-ray in the samples is greater than 3.78 μm.
[1] Liu, J.; Saw R. E.; Kiang Y.-H. Calculation of Effective Penetration Depth in X-Ray Diffraction for Pharmaceutical Solids. Journal of Pharmaceutical Sciences 2010, 99, 3807–3814.
Point 8: Please report the accuracy of the texture coefficient values.
Response 8: We thank the reviewer for raising this question. Many literature [1-3] used texture coefficient to express the orientation of each crystal plane. For Ta coatings, Lin lin Liu et al. [4] used the formula showed in the manuscript to calculate texture coefficient of pure α-Ta. They reported that for a TC(hkl) value greater than 1, a preferred orientation is developed toward a specific crystalline plane; while a TC(hkl) value close to 1 signifies a more random orientation, and a TC(hkl) value in the range from 0 to 1 denotes a lack of grain orientation for the specific plane under consideration. In our research, most TC(211) values were greater than 1, indicating a preferred orientation.
[1] Elmkhah H; Zhang TF; Abdollah-zadeh A; Kim KH; Mahboubi F. Surface characteristics for the TiAlN coatings de-posited by high power impulse magnetron sputtering technique at the different bias voltages. Journal of Alloys and Compounds 2016, 688, 820-827.
[2] Bin Peng; Yu X. Xu; Jian W. Du; Li Chen; Kwang Ho Kim; Qimin Wang. Influence of preliminary metal-ion etching on the topography and mechanical behavior of TiAlN coatings on cemented carbides. Surface and Coatings Technology 2022, 432, 128040.
[3] S. Gangopadhyay; R. Acharya; A.K. Chattopadhyay; S. Paul. Effect of substrate bias voltage on structural and mechanical properties of pulsed DC magnetron sputtered TiN–MoSx composite coatings. Vacuum 2010, 84, 843-850.
[4] Liu LL; Xu J; Lu X; Munroe P; Xie ZH. Electrochemical Corrosion Behavior of Nanocrystalline beta-Ta Coating for Biomedical Applications. ACS Biomater Sci Eng. 2016, 2, 579-594.
Point 9: What software package was utilized? “The size distribution histograms were obtained by measuring more than 100 grains from the FESEM images.”
Response 9: We thank the reviewer for raising this question. We used the software “Nano Measurer” to measure grain sizes. Nano Measurer is a simple and easy software for length statistical analysis. It can analyze particle size and particle size distribution. It also can be applied to measure the length, diameter and pore size of micro and nano scale in SEM, TEM and other pictures as well as the inter-particle distance analysis.
Point 10: in the following statement, please cite the relevant literature: “Compared with the studies in other literatures, the Ta coating prepared in this work has good adhesion as well as strong resistance to cracking”
Response 10: We appreciate the reviewer for this kind suggestion. As suggested by the reviewer, we have added the relevant literature in the statement, which can be seen in Page 14.
Reviewer 2 Report
The manuscript titled “Combined effect of substrate temperature and sputtering power on structural evolution and mechanical property of Ta hard coatings” investigates the possibility of manufacturing of alpha-Ta coatings by magnetron sputtering. The alpha-Ta is desirable form as it is less brittle. The Authors shows that by regulating the temperature of substrate and by adjusting power of the magnetron it is possible to obtain the coatings with pure alpha-Ta phase. The mechanical properties like hardness, modulus as well as adhesion were measured for pure and alpha and betha-Ta mixtures. I find this manuscript well written and quite neat. The conclusions are convincing. I think that this work will contribute to the field. Therefore I recommend it for publication providing that belowgiven remarks will be addressed.
The units should be separated by comma i.e.: “100W” not correct “100 W” correct. There are exceptions. Please apply this rule for the whole manuscript.
Table 1. The labels in third row should be bolded likewise in first row.
Figure 1. The heating of the substrate could be depicted the cooling of target is depicted
Fig. 2 – a.u. is reserved for astronomical units. Arb. Unit is advised as a abbreviation.
The ordinates of the insets should be in the same scale e.g. for FWHM. This will make easier to compare results from a, b, c cases.
Why in case of Fig. 2c there are only 2 points for FWHM measurement?
Page 4 - Meanwhile, as can be seen in the top-right corner of Fig.2(a), the FWHM of (110) and (211) decrease with increasing power, indicating better crystallinity at the higher power [19].
The FWHM is related with both crystallite size and the stress of the crystallites. This should be clearly stated by authors. These effects can be separated by Williamson-Hall method. It is expected that crystallite size is increasing with temperature and the stress is reduced. Thus the FWHM decreases. I guess the decrease of FWHM with temperature of substrate is visible in Fig. 2.
I also recommend for Authors quantitative analysis of amporphous phase. The XRD reflections are possible for crystalline form of matter. However when atoms are well dispersed they might not form any reflections. In such a case the background should be increased. Just an advise which might be useful for future work.
Fig. 4. The SEM images shows the smallest size of crystallites for sample C i.e. highest temperature. What is the relation with FWHM? Are the crystals growing for power 175 W?
Author Response
Point 1: The units should be separated by comma i.e.: “100W” not correct “100 W” correct. There are exceptions. Please apply this rule for the whole manuscript.
Response 1: We are grateful for the suggestion. We have revised relevant parts in the whole manuscript.
Point 2: The labels in third row should be bolded likewise in first row.
Response 2: We are grateful for your careful review. We have bolded relevant words in third row in Table 1.
Point 3: Figure 1. The heating of the substrate could be depicted the cooling of target is depicted
Response 3: We are grateful for the suggestion. We have added the heating part in Figure 1, which can be seen in Page 3 of the revised manuscript.
Point 4: Fig. 2 – a.u. is reserved for astronomical units. Arb. Unit is advised as an abbreviation.
Response 4: We thank the reviewer for this kind suggestion. We have changed the units in Figure 2.
Point 5: The ordinates of the insets should be in the same scale e.g. for FWHM. This will make easier to compare results from a, b, c cases.
Response 5: We are grateful for the suggestion. We have set the ordinate to the same scale in Figure 2.
Point 6: Why in case of Fig. 2c there are only 2 points for FWHM measurement?
Response 6: We thank the reviewer for raising this question. We aimed to measure FWHM of (211) plane and (110) plane of α-Ta and compare the results, but the main phase of the coatings at 400℃-125W and 400℃-150W are β-Ta. Therefore, there are only 2 points in Figure 2 (c), which were under the condition of 400℃-100W and 400℃-175W, respectively.
Point 7: 7. Page 4 - Meanwhile, as can be seen in the top-right corner of Fig.2(a), the FWHM of (110) and (211) decrease with increasing power, indicating better crystallinity at the higher power [19].
The FWHM is related with both crystallite size and the stress of the crystallites. This should be clearly stated by authors. These effects can be separated by Williamson-Hall method. It is expected that crystallite size is increasing with temperature and the stress is reduced. Thus, the FWHM decreases. I guess the decrease of FWHM with temperature of substrate is visible in Fig. 2.
Response 7: We are grateful for this suggestion. We have revised this part and clearly analysed the decrease of FWHM, which can be seen in Page 5.
Point 8: I also recommend for Authors quantitative analysis of amorphous phase. The XRD reflections are possible for crystalline form of matter. However, when atoms are well dispersed, they might not form any reflections. In such a case the background should be increased. Just an advice which might be useful for future work.
Response 8: We are grateful for the suggestion. Your suggestion is very pertinent, and we also consider adding the analysis and testing you said to our next paper. I am looking forward to inviting you to review next time. Thank you again for your suggestion.
Point 9: Fig. 4. The SEM images shows the smallest size of crystallites for sample C i.e. highest temperature. What is the relation with FWHM? Are the crystals growing for power 175 W?
Response 9: We thank the reviewer for raising this question. At the substrate temperature of 400℃，the crystallite size will increases with increasing power. As can be seen from Figure 2(c), the diffraction peaks of coatings are getting closer to the standard peak lines with increasing power, meaning reduced stress. Therefore, the increased crystallite size and reduced stress will together promote the decrease of FWHM at 175W.
