Metal dusting behaviour of laser cladded 304L stainless steel enriched with ruthenium

摘要

Metal dusting is a catastrophic corrosion process, which occurs in the temperature range 400-800°C. Ruthenium laser cladded surface coatings were prepared on 304L stainless steel, using a mixture of 304L powder and varied target ruthenium concentrations of 0, 0.5, 2, 5, and 10wt%. Metal dusting resistance of the laser cladded samples was determined by exposing them to toluene gas with a flowrate of 100ml/min, for 72 hours. Surface analysis results obtained by SEM/EDS analysis showed that an oxide scale formed on the surface of all the samples, which flaked in some areas of the 0-10wt% Ru samples. Pits which are often an indicator of the occurrence of metal dusting were observed on the bare metal substrate. The area of the failed oxide as well as the observed defects decreased, with increasing ruthenium. Laser cladding coatings, which contain increased ruthenium content, are beneficial for metal dusting resistance because they increase the incubation time for the onset of metal dusting by forming a dense, protective oxide layer.