Takuro Saga and Masato Yasui
The effect in the hot-dipped aluminizing process of the alloying elements found in steel and the aluminum bath on the oxidation at higth temperature was investigated. The results obtained were as follows: (1) Hot-dipped Al coatings on Si-or Cr-steel has better properties against scaling at high temperature than on plain carbon steel as a result of their own excellent heat resisting properties and a reduction of the diffusion velocity of the alloy layer. (2) Hot-dipped coatings containing Si or Be were found to be less heat-resistant than those of Al only, because the former forms thinner and more spalled alloy layers. (3) The Be-alloyed coating were found to be a little bit more heat-resistant than the Si-alloyed coating in case the alloy layers were inhibited to the same thickness. (4) In cyclic heating and cooling test, the Si-alloyed coating showed weaker adhesion to the base material than the Be-alloyed coating due to the interfacial oxide scale developed on the steel side. (5) The size of the cracks on the alloy layer becomes finer with the increase of Si or Be content. The cause of cracking is mainly due to thermal stress.
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