engleski

Corrosion and Erosion of Heat treated and Boronised Steels

Corrosion and erosion corrosion behaviour of two carbon steels (with 0.20 and 0.45%C respectively) and two alloy steels (a structural CrMo-steel with 0.46%C and a tool MnVCr-steel with 0.91%C) in normalised state (N, as delivered), after heat treatment by hardening and annealing (HT), and after boronising (B) have been investigated. The corrosion of cylindric specimens was provoked by rotation in an acidified NaCl-solution, and the erosion corrosion by rotation in a suspension of quartz sand in the same solution. The conditions ensured turbulent flow of fluids around the specimens and various incidence angles of quartz particles onto their surface. The wear processes were followed up by mass loss determinations, by optical micrography, and by hardness measurements. The heat treatment increases the superficial hardness of specimens 1.2 to 3.3 times, and the boronising 8 to 11 times. On the other hand, the corrosion and the erosion corrosion are to some extent accelerated by the heat treatment, and considerably slowed down by the boronising. It justifies the assumption that the hardness is not the decisive factor for erosion corrosion resistance. Instead of that, this resistance depends before all on the nature and on the proportion of phases on the metallic surface which determines the corrosion resistance too. Obviously, complicated mutual effects exist between corrosion and erosion processes during erosive / corrosive wear of steels.

Corrosion; erosion; heat treatment; boronising; carbon steels; low alloy steels

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