2004 Volume 44 Issue 1 Pages 139-144
Steam oxidation resistance of 80Ni-20Cr and 50Ni-50Cr coatings has been evaluated in our previous study. The coatings were HVOF sprayed onto the modified 9Cr-1Mo steel substrate and the Cr content in the coating played an important role on the steam oxidation resistance. In the present study, effects of Mn and Si present in the powder and hence incorporated into the coatings were studied. In the 80Ni-20Cr coating, Mn segregated to the coating surface during steam oxidation duration of 1 000 h. Si also enriched at the surface of the coating. On the other hand, the 50Ni-50Cr coatings showed the absence of either Mn segregation or Si enrichment in the post-steam oxidized specimen. The results are discussed in conjunction with the diffusion of Mn and Si onto the chromium oxide layer at high temperatures and the influence of Cr content on the diffusion characteristics of these minor elements.