Mechanical properties degradation in a Cr-Mo low-alloy steel pipe after prolonged use for gas transport in a power plant station

Abstract

Some prolonged exposure effects at the high temperatures and pressures characteristic to the steam transport in power station, have been revealed in a 12HMF GOST (13CrMo44 DIN) Cr-Mo low alloy steel pipes, at both macro and microstructural level, by mechanical tests and optical microscopy. After 128625 functioning hours, a marked mechanical degradation was noticed by the values of tensile strength, hardness and toughness that decreased with 14-16 %, 45-48 % and 47-59 %, respectively. This lose of mechanical properties was correlated on one hand to the coalescence of ferrite grains and pearlite islets and on the other hand to a decrease in the anisotropy of the grains morphology.