Diffusion Weldability of IN 738 LC with Alloyed Layer on Bonding Surface by CO₂ Laser

Study on Diffusion Welding Using Alloyed Layer on Bonding Surface (Report 2)

Abstract

Diffusion welding method using alloyed layer of low melting temperature on bonding surface of IN 738LC with CO₂ laser has been studied.
In this report, diffusion weldability of IN738LC with alloyed surface layer was investigated. Alloyed layer was formed by irradiating linearly focused laser beam (Output: 1.8 kW, Scanning Speed: 0.3 m/min) on bonding surface coated with BNi-2 powder (grain size: 74-105μm). After alloyed layer was formed on one specimen, the specimen was bonded to an unalloyed IN738LC specimen under various diffusion welding time and diffusion treatment time. Effect of diffusion welding time was evaluated by direct observation of the isothermal solidification area of the alloyed surface at 1200°C. Observation of microstructures and microanalysis in cross sections were conducted, and the joint strengths were measured.
The results showed that suitable weldment was obtained by using the following condition; welding time 1 hour at 1200°C and diffusion treatment time 10 hours or more.