Initial stages of oxidation of yttrium-implanted pure iron and various steels at 700°C under low oxygen partial pressure

Yttrium-implanted and unimplanted pure iron and various steels were analysed at T = 700 degreesC and under an oxygen partial pressure Po-2 = 0.04 Pa for 24 h to show the yttrium implantation effect on sample high temperature oxidation resistance. Specimen oxidation weight gains were studied by thermogravimetry, and structural analyses were carried out by in situ high temperature X-ray diffraction (XRD) with the same experimental conditions. The aim of this paper is to show the initial nucleation stage of the main compounds induced by oxidation at high temperature according to the initial sample composition and the surface treatment (yttrium implantation). The results obtained by in situ high temperature XRD will be compared to those by thermogravimetry for a better understanding of the weight gain curves observed during oxidation tests. This study constitutes the first stage of a fundamental approach concerning the effects of yttrium implantation on oxidation resistance of pure iron and various steels between 700 degreesC and 1200 degreesC under several corrosive atmospheres. (C) 2001 Elsevier Science Ltd. All rights reserved.