Effect of Pre-Set Coating Thickness on the Quality of Electron Beam Cladding Forming of Aluminum Alloys
Round 1
Reviewer 1 Report
Ni60 powder bed has been used as a clad layer. Ni60 powder layers will have different properties compared to solid Ni60 layers. It was not suitably considered in the model.
The melting point of AA6061 alloy is different from pure aluminum. It seems properties of pure aluminum are used as AA6061 alloy
Author Response
First of all, thank you very much for your valuable advice. I will give the following answers to your two suggestions.
1. Ni60 powder bed has been used as a clad layer. Ni60 powder layers will have different properties compared to solid Ni60 layers. It was not suitably considered in the model.
Response: The preset coating process is thermal spraying process, and the model parameters are Ni60 powder parameters. This article has been modified.
2. The melting point of AA6061 alloy is different from pure aluminum. It seems properties of pure aluminum are used as AA6061 alloy.
Response: The melting point of 6061 aluminum alloy is about 660℃, which is obtained in references 15 and 16.
Reviewer 2 Report
The authors presented a rather ordinary study in which there are a material (he is not new), the type of processing (it is also known). It was conducted traditional numerical calculations using the commercial package of ANSYS (widely known), and finally made experimental verification by the SEM method with microelement analysis. Why the authors believe that the SEM method + EDS analysis are suitable for the verification of the electron beam cladding (EBC) and the thermomechanical simulation - is not clear. The authors must answer when will prepare a revised version of the paper.
The study contains several inaccuracies that require correction and clarification.
- How are the authors going to deliver of Ni60 coating powder during cladding in a vacuum?
- Equation (1) is recorded with an error.
- How will the authors provide the room temperature - 25 C in a vacuum?
- Equation (5). What is the multiplier "3" and why did it appear?
- Simulations of the authors show that the temperature can reach 2536 C. How does this value (temperature) relate to the evaporation temperatures of Al6061 and Ni60 alloys? At such temperatures and even lower aluminum will evaporate. Nickel will evaporate too and the proposed thermal problem (§2.1 and boundary conditions) should be adjusted so that these phenomena were taken into account. Moreover, evaporation for the EBC technology in vacuum is not recommended - and this is the problem as well.
- The authors claim that the stresses and strains were modelling. However, if they showed the formulation of the thermal problem, then the mechanical problem (the main equations, boundary and initial conditions) is not present. It requires correction.
- The authors show 3D schemes of the FE meshing in ANSYS (Fig. 2 and Fig. 6). However, they show only two-dimensional results of calculations for temperature (Fig. 3) and one-dimensional mechanical calculations (Fig. 7). Why does not analyze the temperature distribution over all axes, and at least the diagonal elements of stress and strain tensors are not shown?!
- Fig.8 is a poor quality. The authors should present a good quality photos of the surface after the EBC process.
- If there are cracks on the surface according to authors, the stresses must exceed the limit of the destruction of the cladding material. How can the authors this explain? Also (in Fig. 7), all stresses are positive. Why had cracks occurred?
Author Response
First of all, thank you very much for your valuable suggestions. I will give the following answers to your 10 suggestions.
1.The authors presented a rather ordinary study in which there are a material (he is not new), the type of processing (it is also known). It was conducted traditional numerical calculations using the commercial package of ANSYS (widely known), and finally made experimental verification by the SEM method with microelement analysis. Why the authors believe that the SEM method + EDS analysis are suitable for the verification of the electron beam cladding (EBC) and the thermomechanical simulation - is not clear. The authors must answer when will prepare a revised version of the paper.
Reply: SEM can better see the macroscopic and microscopic structure of the section, and verify whether cracks, pores and other defects occur in places with large thermal stress. EDS can detect whether there is element diffusion between the coating and the matrix, and further judge whether the coating and the matrix have reached a good metallurgical bonding. In addition, EDS can verify the temperature field simulation, and if there is no element diffusion, it indicates that the matrix has not melted.
2.How are the authors going to deliver of Ni60 coating powder during cladding in a vacuum?
Reply: This article uses a thermal spraying process for coating prepositioning, which has been modified in paragraph 3.1 of the article.
3.Equation (1) is recorded with an error.
Reply: Equation (1) has been corrected.
4.How will the authors provide the room temperature - 25 C in a vacuum?
Reply: Ambient room temperature is usually about 25℃. In order to match with the experiment, the initial temperature of the simulation is set at 25℃.
5.Equation (5). What is the multiplier "3" and why did it appear?
Reply: Equation (5) is a Gaussian surface heat source model, which was quoted from literature [13]. The writing error has been corrected.
6.Simulations of the authors show that the temperature can reach 2536 C. How does this value (temperature) relate to the evaporation temperatures of Al6061 and Ni60 alloys? At such temperatures and even lower aluminum will evaporate. Nickel will evaporate too and the proposed thermal problem (§2.1 and boundary conditions) should be adjusted so that these phenomena were taken into account. Moreover, evaporation for the EBC technology in vacuum is not recommended - and this is the problem as well.
Reply: the boiling point of Ni is about 2732℃, 2536℃ has not reached the boiling point temperature. The boiling point of aluminum is 1100℃, and the temperature is about 900℃ when the heat is transferred to the surface of 6061 aluminum alloy. Combined with the experimental results, there should be less stomatal defects and no evaporation phenomenon.
7.The authors claim that the stresses and strains were modelling. However, if they showed the formulation of the thermal problem, then the mechanical problem (the main equations, boundary and initial conditions) is not present. It requires correction.
Reply: in this paper, using the indirect thermal - mechanical coupling and approach to solving the stress field, temperature field analysis of the results as the load, load to find the solution to the stress field structure model.
8.The authors show 3D schemes of the FE meshing in ANSYS (Fig. 2 and Fig. 6). However, they show only two-dimensional results of calculations for temperature (Fig. 3) and one-dimensional mechanical calculations (Fig. 7). Why does not analyze the temperature distribution over all axes, and at least the diagonal elements of stress and strain tensors are not shown?!
Reply: in this paper, the two-dimensional results show temperature calculation (figure 3) is for the convenience of contrast under different thickness changes of the cloud. In this paper, the variation of residual stress in scanning direction and depth direction with different coating thickness is studied.
9.Fig.8 is a poor quality. The authors should present a good quality photos of the surface after the EBC process.
Reply: the figure 8 has been corrected.
10.If there are cracks on the surface according to authors, the stresses must exceed the limit of the destruction of the cladding material. How can the authors this explain? Also (in Fig. 7), all stresses are positive. Why had cracks occurred?
Reply: Data writing errors have been corrected in this paper. The stresses studied in this paper are Von Mises equivalent residual stresses and all stresses are greater than 0.
Reviewer 3 Report
In this work, we simulated the setting of nickel-based coatings on an aluminum substrate by the electron-beam method. The influence of different thicknesses on the distribution of stress fields in the coating is considered. Such results are valuable and, in my opinion, are obtained for the first time. The application of coatings of large thickness and high-performance method allows us to successfully provide a number of functional properties, including an increase in physical and mechanical properties. The paper presents correlations with the results of the experiment of surfacing coatings with a thickness of 1 mm. This raises a few questions:
1. Have you obtained data on the yield strength, modulus of elasticity, plasticity and other properties for the samples under study?
2. What type of powders were used for surfacing, is it possible to add SEM images and chemical composition?
3. The schematic diagram of the surfacing experiment would well complement the picture in the article.
4. More information about aluminum alloy, what condition and chem. compound?
5. Does the initial structure of the aluminum substrate affect the structure of the applied coating?
Author Response
First of all, thank you very much for your valuable suggestions. I will give the following answers to your five suggestions.
1. Have you obtained data on the yield strength, modulus of elasticity, plasticity and other properties for the samples under study?
Reply: The yield strength and elastic modulus of the samples studied in this paper are parameters of stress field simulation obtained from references [16] and [20].
2. What type of powders were used for surfacing, is it possible to add SEM images and chemical composition?
Reply: Surface modification with autosoluble alloy powder, chemical composition added in paragraph 4.2.
3. The schematic diagram of the surfacing experiment would well complement the picture in the article.
Reply: the schematic diagram of figure 1 is the electron beam cladding experiments.
4. More information about aluminum alloy, what condition and chem. compound?
Reply: the matrix used is 6061 aluminum alloy, chemical composition added to the paper.
5. Does the initial structure of the aluminum substrate affect the structure of the applied coating?
Reply: in this paper, the thermal spraying technique will be preset to the aluminum alloy powder on the surface, high adhesion strength, so the initial structure of aluminum plate generally will not affect the structure of the coating.
Round 2
Reviewer 1 Report
The author's response are not convincing to me.
