The hydrogen-induced modification of the properties of the metal surface coated with oil and lubricant

The change of elastic and damping properties of the subsurface layer of iro n and steel due to the coating with mineral oil and lubricants has been fou nd in internal friction measurements. The effects were not observed for oil coated ceramics but did occur for iron and steel charged with hydrogen. In the case of coated metals, the formation of new internal friction peaks, i ncrease in yield strain and increase in density of the slip lines of stretc hed foils were accompanied by the hydrogen uptake, was similar to the case of hydrogen charged metals. The origin of the phenomena is to be the hydrog en evolution from oil and lubricants at their catalytic decomposition, the hydrogen entry into the metal and the hydrogen-dislocation interaction with in the subsurface layer of a metal. The hydrogen-induced modification of th is layer and the possibility of hydrogen-induced softening or hardening sho uld be taken into account in consideration of the tribological contacts. (C ) 2000 Elsevier Science Ltd. All rights reserved.