Solid-State Rotary Friction-Welded Tungsten and Mild Steel Joints

Round 1

Reviewer 1 Report

1.    The nature of the friction welding joints is rather adhesive than diffusive. Absence of intermetallic phases was found in the weld interface on 20 SEM level observation.

Is it contradictory? Adhesive and welding?

2.    Why the UTS values vary greatly?

3.    The maximum friction welded joint strength of 330 MPa, what is about 30% of the tungsten base material. Why the joint fracture occurred at the tungsten base metal? Is it right?

Author Response

Dear Review,

Thank you very much for your valuable comments. 

Our answers you can find below:

1. The nature of the friction welding joints is rather adhesive than diffusive. Absence of intermetallic phases was found in the weld interface on 20 SEM level observation. Is it contradictory? Adhesive and welding?
   Answer.
   You are right. The sentence has been changed like below.
   The nature of the friction welding dissimilar joint is non-equilibrium based on deep plastic deformation without of visible diffusive processes on interface zone.
2. Why the UTS values vary greatly?
   Answer.
   The UTS vary greatly values what could be related to significant differences of residual high stresses and heterogeneous structure of tungsten rods.
3. According to many literature references relatively low strength of the W-steel joints and the craks are lokated on W side becouse significantly high residual stresses located on tungsten side. 
   Answer.
   According to many literature references relatively low strength of the W-steel joints and the cracks located on W side because significantly high residual stresses located on tungsten side. 

Regards
Tomasz Chmielewski on behalf of authors team

Reviewer 2 Report

I have gone through the paper titled “ Solid state rotary friction welded tungsten and mild steel joints”.

 Following were my observations.

1.    The paper has the latest literature reviews to indicate the chosen topic has a present scope.

2.    In line number 41 and 42, “Welds of tungsten with steel as a dissimilar joint of significant difference properties materials find are increasingly needed”. Where exactly it’s needed? Kindly add the application of this joint for the benefit of the readers.

3.    Table  1 data is tested or based on any other source?  If it’s from any other source, kindly cite it.

4.    Table 2 presents the parameters chosen for the study.  In line 83, it is mentioned as Parameters are chosen based on some optimisation models. If it’s a published earlier work, kindly cite it. Or else add details about how these parameters have arrived?

5.     As per your claim there is no intermetallic compounds are formed. Also, the fracture occurs in the interface. Though flash is formed, is there a sufficient bonding that happened between these materials?

6.    Are any trials conducted by varying the selected input parameters?

7.    The paper is well-drafted

Comments for author File: Comments.pdf

Author Response

Dear Reviewer.
Thank you very much for your valuable comments which helped us to improve the paper. Our answers you can find below.

1. The paper has the latest literature reviews to indicate the chosen topic has a present scope.

2. In line number 41 and 42, “Welds of tungsten with steel as a dissimilar joint of significant difference properties materials find are increasingly needed”. Where exactly it’s needed? Kindly add the application of this joint for the benefit of the readers.
- Answer.
Regarding to your comment three references have been added [12-14].

3. Table 1 data is tested or based on any other source?  If it’s from any other source, kindly cite it.
- Answer. 
Data source is manufacturer specification – 3.2 type quality certificate according to EN 10204 containing, among others, a chemical composition.

4. Table 2 presents the parameters chosen for the study. In line 83, it is mentioned as Parameters are chosen based on some optimisation models. If it’s a published earlier work, kindly cite it. Or else add details about how these parameters have arrived?
- Answer.
As previously mentioned, the presented set of parameters was created as a result of multiple welding attempts aimed at obtaining the maximum strength of the joint. As a result of your valuable comments, an article on the results of our research will be prepared in the future, related to the optimisation of welding parameters of tungsten-steel joints.

5. As per your claim there is no intermetallic compounds are formed. Also, the fracture occurs in the interface. Though flash is formed, is there a sufficient bonding that happened between these materials?
- Answer.
Thank you for this question.
It seems that the bonding between tungsten and steel is satisfying becouse the fracture is located on tungsten side (out of direct interface). Phase boundery W-steel is not weakest element of the joint but there is no possible to skip of fact that tungsten has been weakened by welding process.

6. Are any trials conducted by varying the selected input parameters?
- Answer.
At the beginning of the research, many welding tests were carried out in a very wide range of parameters. The parameter window at which the joints of this pair of materials are created at all is very narrow.

7. The paper is well-drafted. 
- Answer. 
Thank you very much for such a nice opinion.

Regards
Tomasz Chmielewski
Behalf of authors team

Round 2

Reviewer 1 Report

Thank you for the patient cooperation of authors.