Degradation of HVOF Sprayed Hastelloy C-276 Local Mechanical Properties after Exposure to High Temperature Corrosion

Abstract

Hastelloy C-276 coating was deposited on stainless steel 1.4923 using HP/HVOF (High Pressure / High Velocity Oxygen Fuel) thermal spraying technology to increase high corrosion resistance. Possible influence of high temperature corrosion on local mechanical properties change of Hastelloy C-276 was also evaluated in this article. High temperature corrosion is corrosion in the molten salts environment. The salt mixture of 59 % Na2SO4 with 34.5 % KCl and 6.5 % NaCl was used in this study. The selected exposure temperatures were 525 °C and 575 °C and the tests for both temperatures were conducted in autoclave for the time interval of 168 h. The coating and salt mixture layer was analyzed using scanning electron microscope (SEM), EDS analysis and nanoindentor (MTS Nanoindenter XP). High temperature resistance of Hastelloy C-276 coating was evaluated based on the changes in coating surface and according to the occurrence of various phases created on the coating surface during this test. It can be assumed that Hastelloy C-276 coating deposited by HVOF technology shows selective oxidation under the salt film.