On the Alloy Layer of Hot Dip Aluminum Coated Stainless Steels

Abstract

Some metallurgical experiments including measurement of thickness change of coated layers and base alloy, microhardness test, microscopic examination, X-ray diffraction analysis, and electron probe X-ray microanalysis were made to determine the composition and the structure of the alloy layer formed on stainless steels, which were dipped in molten aluminum. The results obtained are as follows.
(1) In austenitic stainless steels and iron alloys containing Cr or Ni more than about 20%, the alloy layer consisted of thin pure alloy layer and the mixed layer which was a mixture of Al and FeAl₃ type alloy. And Cr or Ni had a little solubility in this mixed layer. (2) In ferritic stainless steel the alloy layer had the same structure as that of carbon steels. Namely, it was composed of thin FeAl₃ and Fe₂Al₅ type alloy layer. There was an apreciable solubility of Cr in the latter layer. (3) The mechanism of formation of the mixed layer was also discussed.