A glass based coating for enhancing anti-coking and anti-carburizing abilities of heat-resistant steel HP

This paper presents a glass coating to enhance the anti-coking and anti-carburizing abilities of heat-resistant steel HP for solving the serious coking and carburizing problems of the steel in practice. The coating is prepared by sintering the mix of SiO2, BaO, CaO and Al2O3 on the surface of the steel at 1200 °C. The coating is stable chemically, and there is no component reacting with carbon below 1500 °C. For considering the actual condition and presenting the protective abilities of the glass coated specimen, the pre-oxidized specimen of heat-resistant steel HP is prepared by 1 h heat treatment at 900 °C in a furnace, and quick coking and pack-carburizing tests of two specimens are done at the same condition. The quick coking test shows that catalytic coking does not take place on the coating, and the carbon deposited on the surface of the coated specimen is much less than that on the surface of the pre-oxidized specimen. There are much more carbides in the pre-oxidized specimen than that in the coated specimen after the pack-carburizing.