Mechanical Properties and Microstructures of Al2O3/TiC/TiB2 Ceramic Tool Material
, Guangchun Xiao 1,2,*, Lianggang Ji 1,2, Mingdong Yi 1,2, Jingjie Zhang 1,2, Tingting Zhou 1,2 and Chonghai Xu 1,2,3
Round 1
Reviewer 1 Report
The authors have included several changes asked for in previous reviews. That is good.
Cutting experiments were now included, but these need to be better documented.
Labeling of Fig 7 is incomplete.
The surface roughness difference (Ra?) shown in Fig 8 cannot possibly be statistically significant. Similarly, the cutting forces in Fig 9, is that significantly different? And friction of 0.62 vs. 0.59 - is that significant?
In general, the use of two significant numbers in the paper is not good. 5.17 and 6.22 for fracture toughness is not good practice. It is well established that the precision of measuring fracture toughness by indentation is not that good.
Paragraph including lines 183 - 188 is a statement with no evidence. The paragraph following this should be enough.
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Reviewer 2 Report
The work is aimed at the development of ceramic tool material possessing self-repairing ability and the analysis of toughening and strengthening mechanisms in Al2O3/TiC/TiB2 composites.
The paper requires substantial English checking.
Although the paper may be of some interest, there are a lot of shortcomings.
- There is a misprint in title (!) – “ool” material; it should be (supposingly) “tool” material.
- There is uncertainty or inaccuracy in the co-authors’ list. What is …” and 3”? Does it mean “Chonghai Xu1, 2, 3”?
- A great amount of papers has been written on Al2O3/TiC as well as Al2O3/TiC/TiB2 composites. It would be very useful if the authors clearly specify the novelty of the work and the state beyond the state of the art in a field.
- Actually, increase in flexural strength, hardness, and fracture toughness of the materials under consideration is very modest. Therefore, the specific purpose (if any) for fabrication and study of the materials should be clearly explained.
- As titanium diborade is widely studied as reinforcing additive, please explain the motivation and the purpose and the expected improvement in properties and, as it was stated, in self-repairing capability.
- As material is supposed to be used as a cutting tool, it would be useful to specify what kind of materials are going to be cut during exploitation. What could be limitations exerted by hardness of the cut material?
- Please clearly explain what is a “cutting force” this study.
- Please explain the difference between this study and [28]- Chen Z, Ji L, Guo N, Xu C, Zhang S. Crack healing and strength recovery of Al2O3/TiC/TiB2 ceramic tool materials. International 401 Journal of Refractory Metals and Hard Materials. 2020;87:105167.
- Table 1. Was every particle of TiB2 of exactly 1 µm and MgO of 0.5 µm in size?
- 1 – what material (composition) was examined? It is mentioned only in the text, please specify in figure caption, as well.
- How may the composition affect the sintering parameters? Why were, for all materials, the parameters chosen the same?
- It is known that porosity greatly influence the mechanical properties. It would be useful to discuss the porosity level in each material.
- What could be a mechanism of abnormal grain growth when TiB2 content is 15%?
- Taking into consideration table 4, the substantial difference between the average grain size for the composites cannot be concluded; therefore, explanation of difference in the properties cannot be attributed to the difference in the grain sizes.
- L234 – “the grain size is dense”? What do you mean by this statement?
- Was the presence of TiB detected?
- L242 – “The bonding 242 between Al2O3, TiC and TiB2 grains is tight”. What is meant by this statement? What is a measure of a strong bonding? How was it measured?
- What practical information can be obtained from Table 5?
- From Fig. 7 (which is a core of this work), it is not obviously seen that “the cutting edge surface of the ATB tool is covered by molten substance”. The composition of the molten substance is also not proved by, for ex., XRD analysis.
Author Response
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Reviewer 3 Report
The lower readability in Fig. 5b to 5f - I recommend improving the contrast.
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Round 2
Reviewer 1 Report
How were the cutting experiments conducted? What metal?
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Reviewer 2 Report
The manuscript is substantially improved; however, the consultation with a native English speaker will be highly appreciated.
Still, there are several questions.
- The novelty is still not specified as there is a great amount of papers published on Al2O3/TiC as well as Al2O3/TiC/TiB2 systems. No new papers or comprehensive information is added to the introduction.
- As the main feature of Al2O3/TiC/TiB2 composites is the self-repairing ability, which is detailed in [1], the specific point(s) and added value of the publication is still unclear.
- The motivation and the purpose and the expected improvement in properties and, as it was stated, in self-repairing capability should be open for the readers (not just for a reviewer). No explanations are added to the introduction.
- Should be the “same” sintering parameters measure of a success? I suppose much more important to produce defect-free homogeneous materials. In case of the “same” parameters, it is impossible to compare the composites because of great effect of defects, etc. In your case, an influence of composition onto materials quality has been mostly studied. However, for this work, it is of a minor importance.
Author Response
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This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
General Comments
This paper may be an interesting paper related to materials processing and the development of hard and tough microstructures, however, the relationship of the work to the actual tool performance has neither been established nor hypothesized. The paper describes development of a ceramic material and the improvement in strength, hardness, and toughness, however, no cutting or machining experiments were performed or referenced, and it is not at all clear that the developed material would be a better cutting tool. Literature relating the mechanical properties of the material to tool performance and wear exist, but is not highlighted in this paper.
While the English language may be generally correct, there are a lot of awkward sentence constructions that make the paper difficult to read.
Specific comments
A general section on motivation and hypotheses for this work is lacking. At the end of the introduction there is a paragraph that may serve as a sort of motivation, but this is not sufficient. This is where a background on what would make a good cutting tool would fit in. What would be the needed properties, and what testing would need to be perform to link the material properties to the cutting behavior.
2.2 Performance testing of tool materials
No – this section does not describe any performance testing. It describes to some extent the mechanical properties testing, but not sufficiently.
What standard was used to test the strength of the samples? Samples 3 mm x 4 mm x 3.5 mm does not make any sense. How many specimens were teste at each condition?
Same with Hardness, how many indents?
Fracture Toughness? From indentation? Calculated how? Most of these calculations include the Elastic modulus values – which were used and how were they obtained? Again, how many specimens?
3.2 Mechanical properties
What are the error bars in Figure 2? How many samples were tested?
Which of the reported properties are more important for a tool? And why?
Lines 144 – 145 The link between the strength and hardness referred to here is not established.
Line 149 referring to the tool material performance – no such tool performance has been given or established.
3.3 Microstructures
Line 183 refers to refinement of the grain size – what were the actual grain sizes for each material? A table with values and description of how these were measured should be included.
Figure 4 needs better annotation.
Author Response
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Reviewer 2 Report
The authors analyzed the effect of TiB2 on the mechanical and microstructural properties of Al2O3 / TiC / TiB2 composites.
1. What is the origin of the materials used in the experiments? Authors may include this information.
2. In "In order to determine the optimum content of TiB2, ..." to optimize what? The authors talk about optimizing the amount of TiB2 but do not define which variable they want to optimize.
3. In addition, in the tested TiB2 concentration range, was there any optimal concentration that returned a maximum / minimum point, which justified the wording "optimum content"?
4. Regardless of what the authors are trying to say in this part, a greater amount of concentrations, in the appropriate range, should have been analyzed so that one could speak of "optimization". Authors should review the text and give the correct information about what has been done.
5. The authors write "XRD pattern" in the results, without defining the acronym. They must define "XRD pattern" in the methodology. The same is true with "EDS".
6. The authors must describe the details of the parameters used in the equipment for the measurements.
7. The micro-structural analysis performed is poor. In the microstructural analysis, the authors show a result of the XRD pattern of the composite Al2O3 / TiC / TiB2. Which of the TiB2 concentrations was used in this result? Since the authors are studying the effect of TiB2 on the microstructure of the composite, they must show the XRD results for the different concentrations of TiB2.
8. Authors should determine if there has been a significant change in grain size and crystallite size in the produced composites, as an effect of the introduction of TiB2, after sintering. Use hypothesis testing for the difference between the means to confirm the discussion.
9. Raman and / or FTIR analyzes can be used to confirm the superficial or interatomic interaction between the elements and complement the microstructural characterization.
10. Authors must relate the microstructural analysis to the results of the mechanical analysis and the best results .
10. In the analysis by EDS, define the percentage of each element in the samples.
11. "SEM micrograph and EDS element mappings of the fracture are shown in Figure4." Figure 4 does not show this!
Author Response
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Reviewer 3 Report
The authors discusses Mechanical properties and microstructures of Al2O3/TiC/TiB2 ceramic tool material with varying TiB2 content in these composites. The manuscript is well Witten and results are discussed in detail. I am recommending this manuscript for publication.
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Round 2
Reviewer 1 Report
Response to Reviewer 1 Comments
On behalf of my co-authors, we thank you very much for giving us an opportunity to revise our manuscript, we appreciate editor and reviewers very much for their positive and constructive comments and suggestions on our manuscript entitled “Mechanical properties and microstructures of Al2O3/TiC/TiB2 ceramic tool material”. We have studied reviewer’s comments carefully and have made revision which marked in red in the paper. We have tried our best to revise our manuscript according to the comments. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:
Point 1: The relationship of the work to the actual tool performance has neither been established nor hypothesized. Literature relating the mechanical properties of the material to tool performance and wear exist, but is not highlighted in this paper. What would be the needed properties, and what testing would need to be perform to link the material properties to the cutting behavior.
Response 1:
We have revised the article according to the requirements of the reviewers. Our thesis assumes that TiB2, the repair phase in cutting tool materials, not only has self-repair function, but also has toughening and reinforcing function. In order to study its influence on the mechanical properties of matrix materials, mechanical properties were tested to verify it. A mathematical model is added to illustrate the relationship between mechanical properties and cutting performance of cutting tools.
No, this is still not sufficiently established. Any basic book on manufacturing will establish that For ceramic cutting tools it is well documented that the key properties are:[i]
- room temperature and hot hardness,
- toughness and (impact) strength,
- wear resistance,
- chemical stability and inertness,
- thermal shock resistance.
Point 2: 2.2 Performance testing of tool materials.
No – this section does not describe any performance testing. It describes to some extent the mechanical properties testing, but not sufficiently. Here we are looking for actual machining tests for example.
What standard was used to test the strength of the samples? How many specimens were tested at each condition?
Same with Hardness, how many indents?
Fracture Toughness? From indentation? Calculated how? Most of these calculations include the Elastic modulus values – which were used and how were they obtained? Again, how many specimens?
Response 2: We have supplemented the methods, equipment and testing process used in performance testing, and the specific methods are as follows:
In hardness test, bending strength test and fracture toughness test, we tested 5 samples of the same material respectively, and calculated the arithmetic mean of the test results. Then this shall be listed in the experimental procedure. And I assume the error bars are one standard deviation? Five samples is less than usually needed for ceramics. Which 3-point flexure testing standard was followed? These should be referenced.
The three-point bending method is used to test the bending strength of the sample, and the calculation formula is as follows:
In the formula, σf (MPa) is the bending strength of the material, p is the maximum loading load when the sample breaks, h and b are the height and width of the sample (mm), l is the span of the support point, set as 20 mm, and the loading rate is set as 0.5 mm/min.
The hardness of samples was measured by indentation method with Vickers hardness tester. Give the standard test method used as a reference. The selected indenter is diamond tetragonal indenter, and the included angle between its opposite faces is 136. Hardness calculation formula is:
In the formula, HV is the vickers hardness (MPa) of the material and p is the set load, which is set to 196 N in this experiment; Measure the length of diagonal lines of indentation, and take the arithmetic mean as 2a.
The fracture toughness of the specimen was measured by indentation method. The calculation formula is as follows:
In the formula：KIC is fracture toughness of sample material(MPa·m1/2)ï¼›HV is Vickers hardness measured by indentation method(MPa)ï¼›c is half of the crack length pressed by the hardness tester(mm)ï¼›a is half the diagonal length of indentation(mm).
But the details of the methods are still not sufficient in the text, nor are they referenced anywhere. What is the source of this particular KIC formula?
Point 3: Samples 3 mm x 4 mm x 3.5 mm does not make any sense.
Response 3: Our mistake in the size of the test sample in this paper should be 3mmx4mmx35mm, which we have modified in the article. We fixed this error in the paper.
Point 4: What are the error bars in Figure 2? How many samples were tested?
Response 4: The error bars in Figure 2 show the test results of different samples. For each mechanical property test, we selected 5 samples to measure, and took the arithmetic mean of the results. and error bars are one standard deviation?
Point 5: Which of the reported properties are more important for a tool? And why? And how can this be established?
Response 5: The hardness and fracture toughness of ceramic cutting tool materials have great influence on the wear of cutting tools. High flexural strength of ceramic cutting tool material can reduce the brittle fracture such as cutting edge.
Point 6: Lines 144 – 145 The link between the strength and hardness referred to here is not established.
Response 6: Our expression is not accurate enough, and we have modified it according to the opinions of reviewers.
Point 7: Line 149 referring to the tool material performance – no such tool performance has been given or established.
Response 7: We have revised this article according to the reviewer's request. The influence of mechanical properties of tool materials on cutting performance is analyzed by using mathematical model. And revised the wording appropriately.
The mathematical model talks about wear, the performance of a cutting tool is much more than the wear properties. I was actually looking for reference to machining/cutting experiments here. There is a lot of literature on this topic.
Point 8: Line 183 refers to refinement of the grain size – what were the actual grain sizes for each material? A table with values and description of how these were measured should be included.
Figure 4 needs better annotation.
Response 8: According to the comments of reviewers, we have added a grain statistics table in the paper. The method we use is the cross section method. SEM was used to take 200 grains for cross-section structure of materials with different components, and the grain size was measured, and the arithmetic mean value of the measured results was taken.
[i] S. Kalpakjian and S. R. Schmid, Manufacturing Processes for Engineering materials, Prentice Hall, NJ, 2003.
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Reviewer 2 Report
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