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Kaul, R.
- Vacuum Brazing Of Titanium/316L Stainless Steel Transition Joint For Application In Helium Vessel Of Superconducting RF Cavities
Abstract Views :382 |
PDF Views:9
Authors
P. Ganesh
1,
Abhay Kumar
1,
S. C. Vishwakarma
1,
Aniruudha Bose
1,
Ram Kishor Gupta
1,
B. Sindal
1,
S. K. Rai
1,
P. Chinna Rao
1,
P. Ram Sankar
1,
D. C. Nagpure
1,
R. Kaul
1,
G. Mundra
1,
B. Singh
1
Affiliations
1 Raja Ramanna Centre for Advanced Technology, P.O.: CAT, Indore-452 013, IN
1 Raja Ramanna Centre for Advanced Technology, P.O.: CAT, Indore-452 013, IN
Source
Indian Welding Journal, Vol 51, No 3 (2018), Pagination: 59-65Abstract
Superconducting radiofrequency (SRF) cavities would form important part of the proposed Indian Spallation Neutron Source and Accelerator Driven System. The high beta 650 MHz SRF cavity would be enclosed in a cylindrical vessel to hold liquid helium (LHe). Titanium (Ti) is being considered as the material of construction of helium vessel. The LHe inlet supply line and return helium gas pipe line of the helium vessel would be made of 316L stainless steel (SS). This requires a bi-metallic tubular transition joint between Ti and 316LSS, operating at LHe temperature. Vacuum brazing and explosive welding are potential processes for joining these two dissimilar metals, as fusion welding leads to extensive cracking.
In the present experimental study, vacuum brazing was performed to join Ti-pipe/316LSS flange with BVAg8 braze filler metal (BFM). Notable features of the process include use of (i) 5-10 μm nickel electro-plating as a diffusion barrier on SS part for preventing possible iron migration towards titanium while improving surface wettability for BFM and (ii) use of 304 SS plug, shrunk fit into Ti-pipe, for achieving dimensional and profile accuracy of Ti-pipe during machining while also controlling joint gap during brazing process. The brazed joint displayed uniform joint thickness and acceptable level of hermeticity (helium leak rate 2 x 10-10mbar.lit/s) and also sustained six thermal cycles between 293 K and 77 K. Shear strength of Ti-SS brazed specimens, made in sandwich configuration, was found to be in the range of 50-60 MPa, with failure occurring at Ti/braze interface.
Keywords
Vacuum Brazing, Titanium, Stainless Steel 316L, BVAg8, Superconducting Radiofrequency (SRF) Cavities, Intermetallic Phases.
References
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- Influence of UV Irradiation on Corrosion Behavior of 304L SS in 0.1M H2SO4 and 0.5M NaCl
Abstract Views :212 |
PDF Views:1
Authors
Affiliations
1 Raja Ramanna Centre for Advanced Technology, P.O.: CAT, Indore - 452013, Madhya Pradesh, IN
2 Project Student, Shri Govindram Seksaria Institute of Technology and Science, Vallabh Nagar, Indore - 452003, IN
1 Raja Ramanna Centre for Advanced Technology, P.O.: CAT, Indore - 452013, Madhya Pradesh, IN
2 Project Student, Shri Govindram Seksaria Institute of Technology and Science, Vallabh Nagar, Indore - 452003, IN
Source
Journal of Surface Science and Technology, Vol 36, No 1-2 (2020), Pagination: 53–60Abstract
This paper describes an experimental study on the effect of Ultra-Violet (UV) exposure on the electrochemical corrosion behavior of 304L stainless steel in 0.1M H2SO4 and 0.5M NaCl medium. The results of study demonstrate that in NaCl medium, exposure of both UV-A and UV-C shifts the Open Circuit Potential (OCP) in active direction (less noble) as compared to the specimen without UV exposure which indicates less stable passive film. While in sulphuric acid both UV-A and UV-C shifts OCP in noble direction which reflects the stability nature of passive film. In H2SO4 medium, exposure of both UV-A and UV-C assist in improving passivity which is indicated by lower passive current density. In NaCl medium, exposure of both UV-A and UV-C, decrease the pitting corrosion resistance as indicated by lower Epit (pitting potential) and higher Icorr (corrosion current density). In H2SO4 uniform dissolution was observed after each polarization experiment as shown in optical micrographs. In NaCl medium pitting sites are more under both type UV exposures as revealed by microstructure after polarization experiment. EIS (Nyquist plots) showed that exposure of both UV-A and UV-C in NaCl medium specimens have lower polarization resistance (Rp) than without UV exposure. Lower Rp confirms lesser protectiveness of passive film. In case of H2SO4, higher arc radius (Rp) is observed under UV exposure for both UV-A and UV-C.Keywords
Corrosion, Impedance, Open Circuit Potential (OCP), Polarization, Ultra-Violet (UV).References
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