Hot erosion wear and carburization in petrochemical furnaces

High temperature alloy stainless steels used in olefins manufacturing furnaces are exposed to extreme environmental degradation processes inclusive of carburization, oxidation and hot erosion wear. A study was undertaken to understand the hot erosion wear phenomenon in relation to substrate composition, atmosphere, temperature, time and the influence of carburization. An erosion wear test rig was designed and constructed to simulate the wear degradation process up to 1200°C. Results have shown a surprising relationship between erosion wear rate and temperature for the most prominent stainless steel alloy used in the industry. A novel coating technology was developed for mitigation that enables the non-line-of-sight application of protective macro-coatings typically 1 to 5 mm in thickness. Stainless steel coupons treated with these macro-coatings have exhibited an enhanced resistance to both oxidation and carburization. These macro-coatings also provide superior hot erosion wear resistance as compared to the uncoated stainless steel. A thorough examination of the microstructure and micro-mechanical properties of the coatings is presented. Targeted applications include petrochemical furnace fittings (return bends), thermo-wells and transfer-line-exchanger (TLE) surfaces. Commercial furnace trials of the prototype products have been initiated with some prototypes in field trials for over 18 months. Results of both laboratory accelerated testing and field evaluation will be discussed.