Erosion–corrosion in a laboratory-scale coal-firing FBC of various aluminized coatings prepared by low-temperature pack cementation

Using a halide-activated pack-cementation method but at a temperature (600 °C) noticeably lower than normal, an η-Fe2Al5 coating and two δ-Ni2Al3 coatings with and without dispersions of CeO2 nanoparticles were developed respectively on a low-carbon steel and the steel pretreated with an electrodeposited film of Ni or Ni–CeO2. The erosion–corrosion (E–C) performance of the three aluminide coatings during 100 h exposure at ~ 600 °C in a coal-firing laboratory-scale fluidized-bed combustor (FBC) was investigated, by mounting the aluminized samples onto a rig which maintained rotation for accelerating the relative impacting speed of flying solid particles (mainly SiO2 bed materials). The η-Fe2Al5 and the CeO2-free δ-Ni2Al3 coatings experienced an unacceptable recession rate. Compared to the two CeO2-free aluminide coatings, the CeO2-dispersed δ-Ni2Al3 coating offered profoundly improved E–C resistance, because the latter coating was not only strengthened by the CeO2 dispersion and grain refinement, it also could grow a more adherent alumina scale.