Reviewer 1
English Language and Style
( ) English language and style are fine
( ) Minor spell check required
(x) Extensive editing of English language and style required
( ) I don't feel qualified to judge about the English Language and Style
Comments and Suggestions for Authors
- Authors condidered the catbide precipitate extensively in the discussion. However, the composition, especially the carbon content was not provided in the manuscript.
- Authors used SED/EDS results to identify the precipitates. However, EDS alone is not enough to determine the nature of precipitates. Additional analysis like XRD or TEM/SAD may be useful.
- The manuscript is hard to follow due to log sentences which contain multiple ideas with poor grammar. It is advised to correct the errors.
- It may not be proper to determine the optimum HT condition based on the test results at only two temperatures.
Reviewer 2
English Language and Style
(x) English language and style are fine
( ) Minor spell check required
( ) Extensive editing of English language and style required
( ) I don't feel qualified to judge about the English Language and Style
Comments and Suggestions for Authors
Section 1: The authors should site recent studies already published, for example:
Santos, M., Guedes, M., Baptista, R., Infante, V., Cláudio, R.A., “Effect of severe operation conditions on the degradation state of radiant coils in pyrolysis furnaces”, Engineering Failure Analysis, September 30, 2014, DOI: 10.1016/j.engfailanal.2015.02.010
Section 1: The figure 1 is not relevant.
Section 2: Change the title from "2. Experimental section" to "2. Experimental procedure"
Section 2.2: Clarify different levels. Different locations, positions?
Section 3.3: Use a more perceptive scheme for the presentation of the hardness values in Figure 4
Reviewer 3
English Language and Style
( ) English language and style are fine
( ) Minor spell check required
(x) Extensive editing of English language and style required
( ) I don't feel qualified to judge about the English Language and Style
Comments and Suggestions for Authors
This paper investigates heat treatment effect on 45Ni-35Cr-Nb alloy after long term service as ethylene pyrolysis furnace tube at high temperature. The authors obtained 3 samples from the different locations in the used tube and measured the hardness of these samples before and after heat treatment. A decrease in hardness was observed after heat treatment and authors concluded that such a heat treatment can be used for repairing furnace tube by welding etc. The authors provided detailed cross-section analysis by SEM and EDS and tried to correlate the change in hardness with the microstructure variation. The results provide some useful information for this high temperature material. However, this paper needs to be revised by considering following comments:
1. The composition of raw material should be given in the Experimental part as it is important for readers to consider the source of carbides and other precipitates which could be formed before any reaction.
2. In Fig 1a, the alloy composition should be marked to show the possible phases of this alloy at this temperature.
3. Fig 1b showed Fe-Cr-C phase diagram only. If it is the section of Fe-Cr-C phase diagram at a certain content of Ni, the authors should indicate clearly what the concentration of Ni is used for this diagram.
4. The results shown in Fig 4 indicate significant hardness increases in samples 2, 3 and 4, compared with the sample from unused tube, showing possible enhanced carburisation during the usage. Low temperature annealing significantly reduced the hardness of sample 2 but not of samples 3 and 4. The significant decrease in hardness of sample 3 and 4 only occurred in high temperature annealing. If the controlling step in all these 3 samples is the dissolution of chromium carbides, then why do these samples show different performances with different heat treatment? The authors should give the explanation or proper discussion. How about the repeatability of these results?
5. The EDS in Figs 5 and 6 showed clearly the coexistence of Nb and Si, which suggest the enrichment of Nb and Si. How did authors conclude they are Ni3Nb for raw materials and Nb and Si carbides for used materials? Have you done XRD or some other analysis, e.g. TEM to confirm it? If it is based on others’ reports, refs should be added to support it.
6. The mentioned microstructure change shown in Figs 5 and 6 for different samples and heat treatment conditions are not very significant. The reviewer suggests to quantitatively measure the fraction of carbide change before and after treatment. With these data, the correlation between the microstructure and property can be established more clearly.
Reviewer 4
English Language and Style
( ) English language and style are fine
( ) Minor spell check required
(x) Extensive editing of English language and style required
( ) I don't feel qualified to judge about the English Language and Style
Comments and Suggestions for Authors
Authors in this manuscript tried to investigate the potential heat treatments for the repair of the failed furnace tube. Authors mainly used SEM/EDS to characterize the microstructure of the tubes and use HV hardness as an indicator of the weldability of the tube in the repair. In this manuscript, there are several questions that need to be clarified. Therefore, I suggest a major revision.
1. Regarding to Fig. 3, there is no EDS information available and it is not clear how authors identified all the unknown phases. On the other hand, SEM/EDS cannot provide any structural information, so XRD scans can be extremely helpful in determining the phases in the microstructure. The etching of the alloy was not done properly that it is very difficult to tell if those carbides are at GBs vs. in the matrix, as stated in the manuscript.
2. Authors need to explain why NbC and SiC always coincide with each other, especially Si is not a strong carbide former or even inhibits carbide formation most of the time. This leads to another question for the statement on page 9, “thermodynamic and the Gibbs free energy (G) that the significant alloying elements (such as Nb and Si) were quickly activated with carbon atoms and reduced the degree of sanitization”. Why “sanitization”? I think authors try to say Nb is a stronger cabide former, so carbon preferentially combine with Nb rather than Cr so as to avoid the sensitization.
3. Generally speaking, the EDS maps in Figs. 5 and 6 are very similar. The carbides in the Fig. 6 after 900 C treatment may be marginally larger than those in Fig. 5. So it is not very convincing that the heat treatment change the microstructure significantly, even though the hardness suggests so.
4. Authors did not clearly correlate the hardness with the weldability of the tube. Why this is the case?
5. Why Table 1 is important? Why visual inspection is important? Table 1 can be described briefly in the text.
ผู้ตรวจทาน 1 ภาษาอังกฤษและลักษณะภาษาอังกฤษ()และลักษณะดี ()น้อยสะกดคำต้อง (x) แก้ไขภาษาอังกฤษและลักษณะที่จำเป็นอย่างละเอียด ()ไม่รู้สึกไปตัดสินเกี่ยวกับภาษาอังกฤษและลักษณะ ความคิดเห็นและคำแนะนำสำหรับผู้เขียน-Condidered ผู้เขียน catbide precipitate อย่างกว้างขวางในการอภิปราย อย่างไรก็ตาม ส่วนประกอบ โดยเฉพาะอย่างยิ่งเนื้อหาคาร์บอนไม่ได้ระบุในต้นฉบับ-ผู้เขียนใช้ผลลัพธ์ ถูก/EDS ระบุ precipitates อย่างไรก็ตาม EDS เพียงอย่างเดียวไม่เพียงพอที่จะกำหนดลักษณะของ precipitates วิเคราะห์เพิ่มเติมเช่น XRD หรือยการ/ซาดอาจเป็นประโยชน์-ต้นฉบับยากจะเข้าใจได้เนื่องจากบันทึกประโยคที่ประกอบด้วยหลายความคิด ด้วยไวยากรณ์ยากจนได้ คุณควรจะแก้ไขข้อผิดพลาด-มันอาจไม่เหมาะสมในการกำหนดเงื่อนไขเอชทีเหมาะสมตามผลการทดสอบที่อุณหภูมิเพียงสอง ผู้ตรวจทาน 2 ภาษาอังกฤษและลักษณะ(x) ภาษาอังกฤษภาษาและลักษณะดี ()น้อยสะกดคำต้อง แก้ไขภาษาอังกฤษและลักษณะจำเป็นอย่างละเอียด() ()ไม่รู้สึกไปตัดสินเกี่ยวกับภาษาอังกฤษและลักษณะ ความคิดเห็นและคำแนะนำสำหรับผู้เขียนหมวดที่ 1: ผู้เขียนควรไซต์ศึกษาล่าสุดที่เผยแพร่ เช่น:ซานโตส เมตร Guedes เมตร Baptista, R. อองฟองต์ V., Cláudio, R.A. "ผลของสภาพการดำเนินงานอย่างรุนแรงรัฐสลายตัวสดใสขดลวดในเตาเผาชีวภาพ" วิศวกรรมวิเคราะห์ความล้มเหลว 30 กันยายน 2014 ดอย: 10.1016/j.engfailanal.2015.02.010Section 1: The figure 1 is not relevant.Section 2: Change the title from "2. Experimental section" to "2. Experimental procedure"Section 2.2: Clarify different levels. Different locations, positions?Section 3.3: Use a more perceptive scheme for the presentation of the hardness values in Figure 4Reviewer 3English Language and Style( ) English language and style are fine ( ) Minor spell check required (x) Extensive editing of English language and style required ( ) I don't feel qualified to judge about the English Language and Style Comments and Suggestions for AuthorsThis paper investigates heat treatment effect on 45Ni-35Cr-Nb alloy after long term service as ethylene pyrolysis furnace tube at high temperature. The authors obtained 3 samples from the different locations in the used tube and measured the hardness of these samples before and after heat treatment. A decrease in hardness was observed after heat treatment and authors concluded that such a heat treatment can be used for repairing furnace tube by welding etc. The authors provided detailed cross-section analysis by SEM and EDS and tried to correlate the change in hardness with the microstructure variation. The results provide some useful information for this high temperature material. However, this paper needs to be revised by considering following comments:1. The composition of raw material should be given in the Experimental part as it is important for readers to consider the source of carbides and other precipitates which could be formed before any reaction.2. ในฟิก 1a ส่วนประกอบของโลหะผสมเครื่องเฟสของโลหะผสมนี้อุณหภูมินี้สามารถแสดง3. ฟิก 1b พบ Fe Cr C เฟสไดอะแกรมเท่านั้น ถ้าเป็นส่วนของ Fe Cr C เฟสไดอะแกรมที่เนื้อหาของ Ni ผู้เขียนควรระบุอย่างชัดเจนว่าความเข้มข้นของ Ni คืออะไรใช้สำหรับไดอะแกรมนี้4. ผลลัพธ์ที่แสดงในฟิก 4 ระบุความแข็งอย่างมีนัยสำคัญเพิ่มขึ้นในตัวอย่างที่ 2, 3 และ 4 เปรียบเทียบกับตัวอย่างจากหลอดไม่ได้ใช้ การแสดง carburisation ได้รับการปรับปรุงในระหว่างการใช้งาน การอบเหนียวอุณหภูมิต่ำสามารถลดความแข็ง ของตัวอย่างที่ 2 แต่ ของตัวอย่างที่ 3 และ 4 ไม่ ลดลงอย่างมีนัยสำคัญของความแข็งของตัวอย่างที่ 3 และ 4 เกิดขึ้นในอุณหภูมิการอบเหนียวเท่านั้น ถ้าขั้นตอนการควบคุมในตัวอย่างที่ 3 ทั้งหมดเหล่านี้ถูกยุบ carbides โครเมียม แล้วทำไมทำตัวอย่างเหล่านี้แสดงแสดงแตกต่างกัน ด้วยการรักษาความร้อนแตกต่างกันหรือไม่ ผู้เขียนควรให้คำอธิบายหรือการสนทนาที่เหมาะสม วิธีการเกี่ยวกับการทำซ้ำในผลลัพธ์เหล่านี้หรือไม่ 5. EDS ในมะเดื่อ 5 และ 6 แสดงชัดเจนมีอยู่ร่วมกันของ Nb และศรี ที่โดดเด่นของเอ็นบีซีแนะนำ วิธีได้เขียนสรุปจะ Ni3Nb สำหรับวัตถุดิบและ Nb และศรี carbides สำหรับวัสดุที่ใช้หรือไม่ คุณได้ทำ XRD หรือบางอื่น ๆ การวิเคราะห์ เช่นยการยืนยัน ถ้ามันเป็นตามรายงานของคนอื่น refs ควรจะเพิ่มการสนับสนุน6. The mentioned microstructure change shown in Figs 5 and 6 for different samples and heat treatment conditions are not very significant. The reviewer suggests to quantitatively measure the fraction of carbide change before and after treatment. With these data, the correlation between the microstructure and property can be established more clearly.Reviewer 4 English Language and Style( ) English language and style are fine ( ) Minor spell check required (x) Extensive editing of English language and style required ( ) I don't feel qualified to judge about the English Language and Style Comments and Suggestions for AuthorsAuthors in this manuscript tried to investigate the potential heat treatments for the repair of the failed furnace tube. Authors mainly used SEM/EDS to characterize the microstructure of the tubes and use HV hardness as an indicator of the weldability of the tube in the repair. In this manuscript, there are several questions that need to be clarified. Therefore, I suggest a major revision. 1. Regarding to Fig. 3, there is no EDS information available and it is not clear how authors identified all the unknown phases. On the other hand, SEM/EDS cannot provide any structural information, so XRD scans can be extremely helpful in determining the phases in the microstructure. The etching of the alloy was not done properly that it is very difficult to tell if those carbides are at GBs vs. in the matrix, as stated in the manuscript. 2. Authors need to explain why NbC and SiC always coincide with each other, especially Si is not a strong carbide former or even inhibits carbide formation most of the time. This leads to another question for the statement on page 9, “thermodynamic and the Gibbs free energy (G) that the significant alloying elements (such as Nb and Si) were quickly activated with carbon atoms and reduced the degree of sanitization”. Why “sanitization”? I think authors try to say Nb is a stronger cabide former, so carbon preferentially combine with Nb rather than Cr so as to avoid the sensitization.
3. Generally speaking, the EDS maps in Figs. 5 and 6 are very similar. The carbides in the Fig. 6 after 900 C treatment may be marginally larger than those in Fig. 5. So it is not very convincing that the heat treatment change the microstructure significantly, even though the hardness suggests so.
4. Authors did not clearly correlate the hardness with the weldability of the tube. Why this is the case?
5. Why Table 1 is important? Why visual inspection is important? Table 1 can be described briefly in the text.
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