Study on Weldability of Dispersion Hardening Alloy

概要

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Dispersion hardened alloys possess superior tensile properties at elevated temperature and are being developed. In welding of dispersion hardened alloys, some probelms regarding brittleness at the joint caused by cohesion and decomposition of dispersed particles can be pointed out. This study is made on weldability of TD nickel, especially on behavior of dispersed particles in HAZ (including bond of weld) with various thermal cycles, as the first step of study on welding of dispersion hardened alloys. Mechanical properties of dispersion hardened alloys are quite stable under the melting point of its matrix. At higher temperatures below the melting point of Ni-matrix, dispersed particles become spheres. Then a few of particles agglomerate and the size of particles increases. Mechanism of agglomeration and growth of particles are different from those of precipitates of precipitation hardened alloys -Ostwald growth. Once dispersed particles agglomerate, the properties of dispersion hardened alloys are quite lost and can't be recovered. Diffusion bonding is the most suitable welding technique for such alloys, preventing the agglomeration and decomposition of particles and keeping the characteristics of dispersion hardened alloy itself.
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