Powder Diffraction Data of Aluminum-Rich FCC-Ti_1−xAl_xN Prepared by CVD

Round 1

Reviewer 1 Report

The manuscript discusses the structural characteristics of a CVD grown and powder Ti_1-xAl_xN fcc system.  Aims to provide updated and reliable XRD data suitable for a JCPDF card entry. 

Overall, the article is well written and with justified results. I have only some minor issues, which are shown in the list below. 

Line 21 and multiple others: Please define the acronyms in the text.

Line 109: Please explain how the stress-free lattice parameter has been calculated from the sin²ψ method and provide the elastic constants of the material used. If possible, it would be nice to show the uncertainty of this value. 

Line 176 has a large gap/space in the text.

Line 196: Table 2 needs units for the second column and a description for the last two columns.

Author Response

Line 21 and multiple others: Please define the acronyms in the text.

We define the acronyms now.

Line 109: Please explain how the stress-free lattice parameter has been calculated from the sin²ψ method and provide the elastic constants of the material used. If possible, it would be nice to show the uncertainty of this value.

Equation (1) is given for the calculation of the stress-free lattice parameter and we inserted now the elastic constants.

 

Line 176 has a large gap/space in the text.

The gap/space is removed.

 

Line 196: Table 2 needs units for the second column and a description for the last two columns.

For D the unit Å is inserted and the parameters m and N were more accurately specified in the table.

Reviewer 2 Report

The paper report on the determination of the XRD data pure fcc-Ti1-xAlxN phase with high Al content covering the lack of knowledge regarding the X-ray data of fcc-Ti1-xAlxN. The PDF database contains no data of the ternary phase fcc-Ti1-xAlxN and JCPDF cards 00- 37 025-1495 or 00-046-1200 of fcc-AlN has been used for the XRD analysis of such coatings. However, the source of JCPDF card 00-025-1495 is a private communication originating from 1973 where the synthesis method is unclear. The other JCPDF card 00-046-1200 40 bases on the high-pressure synthesis of fcc-AlN and it offers a reliable data file for the binary phase fcc-AlN. But it is desirable to have also one or more JCPDF cards for the 42 ternary system fcc-Ti1-xAlxN similar to the ternary system fcc-TiCxN1-x. Only with such a 43 JCPDF data file it is possible to obtain a better XRD analysis and texture information of Ti1-xAlxN based materials. The aim of the paper is to provide reliable XRD data suited as 45 JCPDF card basing on a fcc-Ti1-xAlxN powder prepared by CVD.

The subject matter is appropriate for the Journal;

• the quality of the presentation is sufficient;
• the work contains new and original contributions;
• the conclusions are sound and justified;
• the abstract is informative;
• the title reflects the contents adequately.

I suggest the paper to be published as “Communication” after major revision according to the comments below.

 

Introduction section) Relevant literature should be added on Ti1−xAlxN thin films coatings and their characterization to support the aim and data of the paper.

Results and discussion)

• In Ref. https://doi.org/10.1016/j.jallcom.2003.10.087 at higher aluminium contents (x>0.8), the dominant phase of nanocrystalline Ti1−xAlxN thin films is the hexagonal AlN. What are the reasons of a different result in your coating? At line 102 the authors state: “This points to an increasing phase fraction of hexagonal AlN caused by a depletion 102 of the titanium-containing reactants in the gas flow direction. That means that a pure fcc- 103 Ti1-xAlxN phase is only obtained in the front part and in the middle of the steel foil.”. Can you discuss better this point? How has been solved in the paper?What technique has been used to separate the pure Ti1-xAlxN phase from the AlN one?
• What about reproducibility? This aspect is important. How many samples do you have investigated?
• How EDS has been performed? In how many points of the sample? Have you mapped the coating to understand Titanium distribution?
• The discussion should be better supported by literature, there is a lack of references.

 

 

Author Response

• In Ref. https://doi.org/10.1016/j.jallcom.2003.10.087 at higher aluminium contents (x>0.8), the dominant phase of nanocrystalline Ti1−xAlxN thin films is the hexagonal AlN. What are the reasons of a different result in your coating? At line 102 the authors state: “This points to an increasing phase fraction of hexagonal AlN caused by a depletion 102 of the titanium-containing reactants in the gas flow direction. That means that a pure fcc- 103 Ti1-xAlxN phase is only obtained in the front part and in the middle of the steel foil.”. Can you discuss better this point? How has been solved in the paper?What technique has been used to separate the pure Ti1-xAlxN phase from the AlN one?

1. The Ref. https://doi.org/10.1016/j.jallcom.2003.10.087 (Rafaja et al. 2004) describes Ti_1-xAl_xN coatings prepared with another deposition technology – with the PVD process „Arc evaporation “. In our work a medium temperature CVD process is used which is described in detail for the first time in Ref. [5]. In contrast, all PVD processes have a limit of x = 0.65 for the deposition of the pure cubic fcc-phase. If x > 0.65 than the co-depostion of hexagonal AlN occurs and for values x > 0.8 the layer consists almost completely of hexagonal AlN (see the both new references [3,4]). Our CVD process allows the deposition of pure cubic Ti_1-xAl_xN coatings with x > 0.8.

 

2. But in this work, we used the CVD process because of the high deposition rate for preparing a powder sample with a high content of the cubic Ti_1-xAl_xN phase. This was done in a lab-scale CVD reactor with a limited homogeneity zone and not in an industrial CVD reactor. In flow direction the Ti_1-xAl_xN coating contains an increasing content of AlN because of the depletion of titanium-containing reactant. That means only the first cm of the deposition zone contain the pure cubic phase. But we needed a large substrate 50 x 50 mm for producing enough powder. So, we have in the powder a mixture of the dominating cubic Ti_1-xAl_xN phase and few hexagonal AlN. But the flake of the free-standing Ti_1-xAl_xN layer consists of the pure cubic phase how we could show by SEM and SAED/HRTEM.

 

3. Generally, for X-ray analysis it was not necessary to separate the cubic phase. We extracted the diffractogram of the cubic phase from the powder diffractogram by a deconvolution procedure in the Rietveld analysis (using software TOPAS) with the two phases having different lattice parameters and/or spacegroups. The result of the calculation is shown in Fig. 8.

 

• What about reproducibility? This aspect is important. How many samples do you have investigated?

We applied well-known CVD conditions for the manufacture of a Ti_1-xAl_xN coating with x > 0.8 and a high content of the cubic phase. The main point was to produce enough Ti_1-xAl_xN powder for the X-ray analysis.

• How EDS has been performed? In how many points of the sample? Have you mapped the coating to understand Titanium distribution?

Mapping of titanium distribution was not required because we know from earlier investigations which CVD process conditions give a Ti_1-xAl_xN coatings with defined value x. Above that, we have measured 5 different points and determined the mean value.

• The discussion should be better supported by literature, there is a lack of references.

1. We added two references [3,4] which show more clearly the deposition area of the cubic phase in PVD processes. But in this work the focus was to prepare a powder diffraction file from a Ti_1-xAl_xN sample which has a high quality and where we can produce sufficient powder material. In our view the number of references with the two additions should be sufficient for this purpose. PVD processes are now described by [1,3,4] and the review paper [2] as well as the CVD process is also described by [5-7]. The powder diffraction file is useful for coatings prepared by both technologies. Details regarding the applied CVD process were described in Reference [5].

Reviewer 3 Report

This paper is on the diffraction studies of a titanium alloy coating consisting of Al and N. The alloy has a face centered cubic structure. The major contribution lies in the new data of XRD analysis. The method is well designed and the data support conclusions. 

The following changes may be made before the consideration for publishing in Coatings.

1. In the title, "fcc" may be modified as "FCC" because in the materials science field, the face centered cubic structure is abbreviated as "FCC".
2. IN the Abstract, "such coatings basing on experimental data" may be changed into "such coatings based on experimental data".
3. In Figure 2, if possible, the crystallographic planes may be marked for each or typical diffraction peaks.
4. The unit in Eqn (1) may be removed. Or just simplified as "nm" instead of "in nm".
5. It would be nice to have the diffraction peaks in Figure 8 marked with the crystallographic planes (in Miller Indices). 
6. Check the citation style and writing in the reference part. For example, in reference item [2], "Mat. Sci. and Eng. A" should be "Mat. Sci. Eng. A".

Author Response

The following changes may be made before the consideration for publishing in Coatings.

1. In the title, "fcc" may be modified as "FCC" because in the materials science field, the face centered cubic structure is abbreviated as "FCC".

fcc is changed to FCC in the title. But generally, both notations are common: fcc and FCC. In our references you can also find the notation fcc.

2. IN the Abstract, "such coatings basing on experimental data" may be changed into "such coatings based on experimental data".

Based is inserted.

3. In Figure 2, if possible, the crystallographic planes may be marked for each or typical diffraction peaks.

The crystallogrphic planes are inserted.

4. The unit in Eqn (1) may be removed. Or just simplified as "nm" instead of "in nm".

Is simplified as „nm“ in Eqn 1 and 2.

5. It would be nice to have the diffraction peaks in Figure 8 marked with the crystallographic planes (in Miller Indices).

The crystallographic planes are also inserted in Fig. 8.  

6. Check the citation style and writing in the reference part. For example, in reference item [2], "Mat. Sci. and Eng. A" should be "Mat. Sci. Eng. A".

Citation style is checked and changed in [2] and [15].

Round 2

Reviewer 2 Report

The authors have clarified and replied to all the addressed points. I suggest the paper to be accepted.