In order to apply diffusion bonding to a radiant tube made of heat resisting steel castings, the relation between bonding strength of joints and Ni content in insert metals has been investigated. Then the bonding strength was evaluated by tensile tests at 1 273 K as well as creep rupture tests of 1 273 K-9.8 MPa.
Quantity of voids caused with kirkendall effect at the bonded zones heated at 1273 K either for 1800 ks or 1 224 ks in N
2 gas has been investigated.
The results obtained are summarized as follows:
(1)The joints were bonded with the insert metal of Ni foil or Fe-Ni alloy varied from 10% to 45% of Ni contents in order to improve the bondability. Their tensile strength as bonded was hardly affected with Ni contents. On the contrary, quantity of voids gradually increased in proportion to the difference between Ni contents in the base metal and the insert metals after heating of 1 273 K×1 800 ks.
(2)The joint bonded without an insert metal was as excellent as the base metal in the creep strength and the tensile strength.
(3)The joint bonded with the insert metal of similar composition to the base metal was as almost strong as the base metal in the high temperature properties.
(4)Concerning with bonding atmosphere, the joint bonded in N
2 gas was as almost strong as that bonded in vacuum in the high temperature properties.
View full abstract