In recent decades metal dusting has become a costly problem in waste heat recovery systems for various petrochemical processes. There exists a base of experience in the heat treating industry which provides additional information regarding alloy selection for metal dusting environments. Carbon and low alloy steel machine parts are often surface carburized in an atmosphere of N₂, CO, H₂ and CH₄. Metal dusting is a common occurrence in the cooler zones of the furnaces used. The relative performance of materials used for furnace fixturing has been established by experience. Alloy ranking from long term test programs now in progress correlates well with this experience.