Abstract
The dissolution phenomenon of the base metal into the liquid insert metal during the transient liquid insert metal diffusion bonding (TLIM bonding) of Ni base superalloy MM-007 was investigated. The influence of the oxide film on the dissolution phenomenon of the base metal into the liquid insert metal was also investigated.
Main experimental results obtained in this research are as follows;
(1) The dissolution of the base metal into the liquid insert metal occurred preferentially at dendrite boundary.
(2) The dissolution phenomenon of the base metal into the liquid insert metal can be described by Nernst-Brunner's theory.
(3) In the early stage of dissolution process, dendrite boundaries in oxidized base metal were preferentially dissolved and subsequently dissolved zones linked each other.
(4) In the dissolution process, oxide film was seperated from the base metal and subsequently moved toward the center of the bonded interlayer.
(5) The dissolution process of oxidized base metal was divided into three stage according to the dissolution rate constant K. In the Stage I, K value is smaller than that of the base metal without oxidation. In the Stage III, K value is same as that of the base metal without oxidation. Stage II is the transient stage on K value. The change of K value is due to the behavior of oxide film. Namely, in Stage I, the oxide film is stable and prevents direct condact of the liquid insert metal to base metal. However, in Stage II, the oxide film is torn and the liquid insert metal conducts to the base metal without any interruption.
(6) In the Stage I, the dissolution rate was reduced as thickness of the oxide film increased. The decrease in the dissolution rate is due to the decrease in the diffusion flux of B into the liquid mating base metal through the oxide film with the increase in the thickness.
