Research on Microstructure and Mechanical Properties of Wide-gap Brazed Joints of K465 Superalloy Using Nickel-base Brazing Filler Metal

Abstract

The joint clearance with 0.5mm was brazed with pre-filled high-melting powder method, by using K465 nickel-base superalloy as base metal, FGH95 nickel-base superalloy powder as pre-filled powder. The effects of different holding time on microstructure and mechanical properties were investigated. The results show that the brazing seam microstructure of the joints brazed at 1220℃ for 0.5h composes of alloy powder particles and phases among the particles. The microstructure is a two-phase structure of γ and γ' inside the powder particles, and among the particles are γ and γ' two-phase based borides, silicides and γ+γ' eutectics. With the increase of holding time, the powder particles grow bigger, the compounds and γ+γ' eutectics merge together, leads to the decrease of the amount of compounds and γ+γ'eutectics. The holding time is prolonged from 0.5h to 16h, the average rupture life increases from 31.59h to 54.58h, but it is not easy to achieve the isothermally solidified joints with good mechanical properties.

Keywords

• brazing
• K465 nickel-base superalloy
• microstructure
• mechanical property