The uniform composition of a thermally sprayed duplex stainless steel coatings is essential to ensure its good corrosion resistance in salt water. Stainless steel coatings made on 4130 steel substrates by atmospheric plasma spraying (APS) always contain pores and oxides accompanied with chromium-depleted zones which destroy the corrosion resistance of such coatings. To reduce porosity and oxidation of the coatings, several post treatments for the coatings sprayed by APS and by APS with gas shielding around the plasma jet (APS/S) were studied, including resin impregnation, hot isostatic pressing (HIP), shot peening and vacuum annealing. Electrochemical corrosion tests revealed that the corrosion resistance of the APS coatings could not be improved by any post treatments because oxidation during spraying caused chromium-depleted zones in the coating. The best corrosion resistance was obtained by using the shielding gas shroud with APS. Such coatings had a very low oxide content and primarily ferritic structure. The corrosion resistance of these APS/S coatings can be further improved by shot peening to densify the coatings or by post annealing, which balances the austenite /ferrite ratio of the coating as well as reduce porosity.
|Title of host publication||Proceedings of the 1994 Thermal spray industrial applications|
|Number of pages||6|
|Publication status||Published - 2 Jun 1994|
|MoE publication type||A4 Article in a conference publication|
|Event||7th National thermal spray conference: Thermal spray industrial applications - Boston, United States|
Duration: 2 Jun 1994 → 24 Jun 1994
|Conference||7th National thermal spray conference|
|Period||2/06/94 → 24/06/94|
Kinos, T., & Kettunen, P. (1994). Effect of Post Treatments on the Corrosion Resistance of Plasma Sprayed Duplex Stainless Steel Coating in Salt Water. In Proceedings of the 1994 Thermal spray industrial applications (pp. 537-542). ASM International.