Metal dusting of high temperature Cr-Ni steels and Ni-base alloys

摘要

Metal dusting (MD) is a special kind of high temperature corrosion leading to a disintegration of steels and Ni-base alloys into a dust of metal particles, oxides, carbides and carbon under formation of pits or in form of a general overall attack of the surface. It occurs at temperatures from 450℃ to 800℃ in carburizing atmospheres or, more commonly, in carburizing and selectively oxidizing atmospheres. MD is a widespread problem in the industry, particular in all kinds of furnaces and reforming units. Nowadays, the life time of some components in case hardening furnaces is limited to approx. 1.5 years due to MD attack. For economic reasons life times above 3 years are aspired. Only a few scientific publications focused on a quantitative characterization of the MD resistivity of typical high temperature steels and Ni-base alloys used for case hardening furnaces. Thus, the manufacturers of case hardening furnaces had to rely on the data sheets of the suppliers of the steel and Ni-alloys. Therefore, a MD test facility was developed and constructed which allows simulating the typical conditions in case hardening furnaces in order to quantify the MD behavior of several high temperature steels and Ni-base alloys. The MD results of these alloys were compared with industrial damage events. Additionally, the MD mechanisms of steels and Ni-base alloys were examined by microprobe analysis.