Effect of Cu Interlayer on the Microstructure and Strength for Brazing of Tungsten/316L Steel
- PDF / 2,075,952 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 75 Downloads / 198 Views
ÓASM International 1059-9495/$19.00
Effect of Cu Interlayer on the Microstructure and Strength for Brazing of Tungsten/316L Steel Meng Wang, Yuanting Chen, Xianfen Li, Peng Hua, Linfeng Gao, Wei Zhou, and Yucheng Wu (Submitted September 10, 2017; in revised form November 27, 2018) Brazing is an effective technique for joining tungsten and steel. However, the high residual stresses are produced due to the different coefficients of thermal expansions between tungsten and steel. Compared with the direct brazing with BNi-2 foil filler, BNi-2/Cu/ BNi-2 multiple interlayer was used as filler to minimize the residual stresses between tungsten and 316L steel. The brazing experiments were conducted at 1050 °C for 25 min using Cu foils with different thickness. The results show that tungsten and 316L steel have been successfully joined by brazing. The intermetallic compound of NiW formed at the W/BNi-2 interface, which was detrimental to the strength of the joint. The microhardness of different diffusion zones is higher than that of the substrates owing to the formation of intermetallic compound and solid solution. All specimens of shear testing fractured at the W/BNi-2 interface close to W substrate, and the average strength of joints was 197, 275 and 268 MPa with multiple interlayer thickness of 0.2 , 0.1 and 0.05 mm copper foil, respectively, while the average strength of joints was 143 MPa with BNi-2 foil filler. The significant increase in the joint shear strength can be ascribed to the Cu foil in the multiple interlayer because of with excellent plasticity and toughness. Keywords
316L steel, brazing, microstructure, shear strength, tungsten
1. Introduction Divertor works in a complicated environment with high heat flux, high particle flux and heavy neutron irradiation (Ref 1). Appropriate plasma facing material (PFM) is important to enhance the lifetime of the component itself (Ref 2). Due to the advantages of low activation, high Z material, high thermal conductivity, high sputtering resistance and low deuterium/ tritium retention (Ref 3, 4), tungsten is considered as one of the most promising divertor materials. However, tungsten is difficult to machine due to its brittle nature at room temperature. For a divertor, tungsten and steel usually used as first wall material and structural material, respectively. The joining of these two materials is essential to a divertor (Ref 5). Due to their huge differences in physical properties of these two materials, such as different melting points (Tm: 3407 °C for tungsten and 1300-1500 °C for steels) and large mismatch of coefficients of thermal expansion (CTE: 4.5 9 10 6 k 1 for tungsten and 10-18 9 10 6 k 1 for steels), large residual stresses appear along the bonding interfaces. Therefore, traditional fusion welding is inapplicable to join tungsten and steels. It has been reported that brazing and solid-state diffusion bonding have been an ideal method to join tungsten and steels.
Meng Wang, Yuanting Chen, Xianfen Li, Peng Hua, Linfeng Gao, and Yucheng Wu, School of Materials Scien
Data Loading...
