The behaviour of the natural oxide of MANET as permeation barrier under cyclic loads: Self-healing

Abstract

A gas permeation technique has been employed to determine hydrogen permeation rates for oxidised tubular MANET ( MArtensitic for NET) specimens under cyclic tensile loads. The results obtained over the temperature range 400–873 K and for driving pressures of 100 kPa indicate a permeation reduction factor (PRF) of up to 100. Similar measurements performed under cyclic tensile loads (220 MPa 35% UTS, cyclic rate 10 min/cycle) resulted in a PRF of only 50. However, continuous measurements under tensile cyclic load, i.e. the sample was kept in contact with the hydrogen (with ∼1000 ppm H 2O) for an extended period, has shown a recovery of the initial PFR implying the possibility of barrier self-healing.