The corrosion behavior of four grades of valves steels i.e. X33CrNiMn23-8, X50CrMnNiNbN21-9, X33CrNiMnN23-8, X50CrMnNiNbN21-8, X53CrMnNiN20-8 and X55CrMnNiN20-8 in combustion gases of petrol with different of ethanol volume percentage has been studied. In this work, the results of kinetic oxidation of above mentioned valve steels in combustion gases of petrol-ethanol mix with 5,10, 50 % [v/v] of ethanol are presented. It has been found that increase of ethanol in a petrol-ethanol mix up to 50 % ethanol volume percentage decreases corrosion resistance of examined steels.The corrosion tests have been performed gravimetrically under thermal shock conditions by heating of specimens from room temperature up to 1173 K. After heating at 1173 K for two hours, specimens were quenching at room temperature for 20 minutes and again heated. This experiment simulated the working conditions of a highly thermal loaded exhaust valves in spark or self-ignited combustion engines. The analysis performed shows that the corrosion resistance of X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8 valve steels in an environment of combustion gases from petrol with 50 % ethanol additive (v/v) is significantly worse than in an environment of combustion gases of petrol-ethanol mix with 5 and 10 % [v/v] of ethanol.Keywords: valve steels, combustion gases, petrol-ethanol mix, kinetic of oxidation
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