Effect of Cooling Rate on Hardness and Phase Transformation of a Pd-Ag-Based Metal–Ceramic Alloy with or without Ice-Quenching

Round 1

Reviewer 1 Report

There are some issues which should be corrected or improved:

• Table 5 The values of hardness should be rather presented in a proper unit not as values measured in the Hardness scale.
• Table 5 Even if the hardness value is presentes as it is in Table 5 the values should be given without numbers after dots. Moreover the mesurement errors sholud be estimated and considered in analysis of results.
• Remark to 3.3 Phase transformation, XRD diagrams and comment- on the diagram there are marked the peaks of the α,β and β’ phase , in comment to the HRD should be given information to what phases they are correspond for example α to Pd rich phase and so on. The presented after XRD diagrams in manuscipt results of FE-EPMA confirmed what was find in XRD, that the α- Pd rich matrix and β-InPd3-based preciptations.
• Fig. 6 In caption should be given information –explenation of SP, P, M, there is such explentaion under the Table 6 but first is presented Fig. 6 so the explenation should be at once in caption of Fig.6.
• Conclusions should be developed. In presented form conclusions are to general.
• There are some mistakes which must be corrected:

Fig. 4 it is rather Fig.4-2, moreover, there is no information what represent on this diagaram blue dot-line

The same remark as above to the Fig. 3 it is rather Fig. 3-1

Table 5 is twice, it must be corrected, also in text must be corrected numbers of tables.

Caption to Fig. 3-3 should be replaced.

Author Response

Comments and Suggestions for Authors

Reviewer1

There are some issues which should be corrected or improved:

Table 5 The values of hardness should be rather presented in a proper unit not as values measured in the Hardness scale.

→It has been revised as indicated by a reviewer (kgf/mm²).

• Table 5 Even if the hardness value is presentes as it is in Table 5 the values should be given without numbers after dots. Moreover the mesurement errors sholud be estimated and considered in analysis of results.
• →It has been revised as indicated by a reviewer.
• Table 5-2. Mean surface hardness (HV0.3) and standard deviations.

Cooling rate	Mean, kgf/mm2 (SD)
	Oxidation	Wash	Opaque	Main bake	Glaze
S0¢	163Aa	297Be	289Bd	266Bc	256Bb
	(2.08)	(3.24)	(4.12)	(3.08)	(3.89)
S0	303Ce	296Bd	288Bc	264Bb	253Ba
	(2.82)	(4.11)	(2.75)	(3.42)	(2.72)
S3¢	164Aa	275Ae	270Ad	242Ac	235Ab
	(3.03)	(2.72)	(2.40)	(4.26)	(3.17)
S3	257Bc	277Ae	269Ad	241Ab	235Aa
	(5.62)	(4.82)	(4.81)	(3.90)	(3.49)

•  
• Remark to 3.3 Phase transformation, XRD diagrams and comment- on the diagram there are marked the peaks of the α,β and β’ phase , in comment to the HRD should be given information to what phases they are correspond for example α to Pd rich phase and so on. The presented after XRD diagrams in manuscipt results of FE-EPMA confirmed what was find in XRD, that the α- Pd rich matrix and β-InPd3-based preciptations.

→It has been revised as indicated by a reviewer.

3.3. Phase transformation

• Figure 4-1 and 4-2 show the XRD results at the oxidation and glaze steps, respectively. The α phase corresponds to the f.c.c. Pd-Ag-rich phase with a lattice constant of a = 3.994 Å; the β phase corresponds to the InPd₃-based phase with a tetragonal structure and lattice constants of a = 4.119 Å and c = 3.673 Å [10]. The β¢ phase corresponds to the metastable InPd₃-based phase that has a c/a ratio larger than that of the stable InPd₃ (β) phase.
•  
• Fig. 6 In caption should be given information –explenation of SP, P, M, there is such explentaion under the Table 6 but first is presented Fig. 6 so the explenation should be at once in caption of Fig.6.

→It has been revised as indicated by a reviewer.

• Figure 6. FE-SEM image of GL-S0¢ and GL-S3 (M: matrix, P: precipitate in grain boundary, SP: precipitate in grain interior).
•  
• Conclusions should be developed. In presented form conclusions are to general.
• →It has been revised as indicated by a reviewer.
• Oxidation followed by ice-quenching allowed the alloy to be in a homogenized state. The oxidation-treated specimens followed by cooling at relatively high or low cooling speeds showed much higher hardness than the ice-quenched specimen after oxidation, which was resulted from the formation of the metastable precipitates based on the InPd₃ phase with tetragonal structure. The hardness of ice-quenched alloy after oxidation was recovered in the very next firing step at both, the relatively high and low cooling rates. In all specimens, the Pd-rich matrix and the InPd₃-based precipitates were observed after the final step (glaze).
•  
• There are some mistakes which must be corrected: Fig. 4 it is rather Fig.4-2, moreover, there is no information what represent on this diagaram blue dot-lineTable 5 is twice, it must be corrected, also in text must be corrected numbers of tables.
• The same remark as above to the Fig. 3 it is rather Fig. 3-1
• →It has been revised as indicated by a reviewer.Caption to Fig. 3-3 should be replaced.
•  
• →It has been revised as indicated by a reviewer.

Figure 3-3. Microstructure of additional heat-treated GL-(S0¢)IQ (5000×).

 

Thank you very much for your careful review.

Reviewer 2 Report

The aim of the paper, i.e. the effect of cooling rate on hardness and phase transformation of a Pd−Ag-based metal-ceramic alloy with or without ice-quenching, is quite interesting. The abstract summarize the work. The purpose of the study is clearly outlined and the findings of prior work are well discussed. There are no errors in logic or experimental procedure. The authors accurately explain how the data were collected. There is sufficient information that the experiment can be reproduced. All topics are well presented and discussed. The summary and conclusions are sound and justified. All presented figures are good quality and they prove their point. The paper is written in good English. The manuscript is easily readable concerning language, style and presentation. The references are appropriate and up to date.

Author Response

Thank you very much.

Reviewer 3 Report

Comments:

Part 3.2

Line 157: Mark contained precipitation in Figure 3

Line 160: Show the precipitation in Figure 3 – where is it??

Line 162: How much finer?? → in % or in dimensions

 

Part 3.3.

Figure 4.1. and Fig. 4 (line 205) –all peaks marked with the phases (depending on the chemical elements included in the phases)

It is not clear what phases were determined with XRD analysis

Line 211: Little oxygen (please write in at.%)

 

Results of HV – please write example HV5 as a value of HV  (which is commonly used for dental alloys) – according to the Standard

Improve Discussion in sector lines 230-240 – operate with value or with %. Please write how much one value is higher than the other, not in general as described now

Please improve indication – line 244 … how do you think it is possible to confirm hardness with XRD?? XRD is used to identify phases and indirectly, by this, we can explain other mechanisms. Please correct this statement

 

Conclusions - should be written more transparently, precisely

Comments for author File: Comments.pdf

Author Response

Comments and Suggestions for Authors

Comments:

Part 3.2

Line 157: Mark contained precipitation in Figure 3

Line 160: Show the precipitation in Figure 3 – where is it??

Line 162: How much finer?? → in % or in dimensions

•  
• →It has been revised as indicated by a reviewer.

• 2. Changes in microstructure

• Figure 3-1 shows the microstructure of the specimens after oxidation. The as-cast specimen (As-cast) showed an equiaxed structure and contained precipitates in the grain boundary (arrow mark) and grain interior (double arrow mark). In the OX-IQ specimen, which was ice-quenched after oxidation, precipitates disappeared due to homogenization. However, by cooling the oxidation-treated specimens at S0 and S3 (OX-S0, OX-S3), precipitates formed in the grain boundary (arrow mark) and grain interior (double arrow mark). The grain boundary precipitates were similar in both the specimens, but the grain interior precipitates were much finer (less than 30%) in the OX-S0 specimen than in the OX-S3 specimen.

Part 3.3.

Figure 4.1. and Fig. 4 (line 205) –all peaks marked with the phases (depending on the chemical elements included in the phases)

It is not clear what phases were determined with XRD analysis

→It has been revised as indicated by a reviewer.

3.3. Phase transformation

• Figure 4-1 and 4-2 show the XRD results at the oxidation and glaze steps, respectively. The α phase corresponds to the f.c.c. Pd-Ag-rich phase with a lattice constant of a = 3.994 Å; the β phase corresponds to the InPd₃-based phase with a tetragonal structure and lattice constants of a = 4.119 Å and c = 3.673 Å [10]. The β¢ phase corresponds to the metastable InPd₃-based phase that has a c/a ratio larger than that of the stable InPd₃ (β) phase.Line 211: Little oxygen (please write in at.%
•  

-> The oxygen content was confirmed only by FE-EPMA mapping, but the content was negligible, so quantitative analysis by FE-EPMA spot analysis was not performed. Please understand that additional experiments could not be conducted due to tight time, but it does not seem to affect the results.

 

 

Results of HV – please write example HV5 as a value of HV  (which is commonly used for dental alloys) – according to the Standard

→It has been revised as indicated by a reviewer.

 

3. Results

3.1. Hardness measurement (HV0.3)

Table 5-2. Mean surface hardness (HV0.3) and standard deviations.

 

 

Improve Discussion in sector lines 230-240 – operate with value or with %. Please write how much one value is higher than the other, not in general as described now

→It has been revised as indicated by a reviewer.

In particular, the rapidly cooled specimens (S0) showed the 8% higher hardness through the glaze step (p < 0.05), indicating that the optimum cooling rate to maintain a high hardness has a relatively high value (S0).

 

Please improve indication – line 244 … how do you think it is possible to confirm hardness with XRD?? XRD is used to identify phases and indirectly, by this, we can explain other mechanisms. Please correct this statement

 →It has been revised as indicated by a reviewer.

XRD was performed to investigate the phase transformation according to the multiple firing simulation of each specimen.

 

Conclusions - should be written more transparently, precisely

• →It has been revised as indicated by a reviewer.
• Oxidation followed by ice-quenching allowed the alloy to be in a homogenized state. The oxidation-treated specimens followed by cooling at relatively high or low cooling speeds showed much higher hardness than the ice-quenched specimen after oxidation, which was resulted from the formation of the metastable precipitates based on the InPd₃ phase with tetragonal structure. The hardness of ice-quenched alloy after oxidation was recovered in the very next firing step at both, the relatively high and low cooling rates. In all specimens, the Pd-rich matrix and the InPd₃-based precipitates were observed after the final step (glaze).Thank you very much for your careful review.
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Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

No comments.