Chromium depletion in the vicinity of carbides in sensitized austenitic stainless steels

摘要: The analytical electron microscope (AEM) was used to examine the microstructure of type 316LN stainless steel alloys which had been annealed for 50 300 hours in temperature range 600 700 °C. M23C6 carbide chemistry and distribution are described as a function heat treatment.X-ray spectroscopy AEM revealed significant chromium depletion at grain boundaries vicinity carbides samples aged 100 650 °C °C, with lower boundary values observed than width depleted zone normal increased increasing annealing time and/or temperature. Measurements concentration along away from were made after aging hours, level rose steadily until bulk value reached distance ~3μm carbide. same sample an order magnitude less. Some molybdenum also found boundaries, Mo-depletion profiles form extent similar results. Simple thermodynamic models calculate equilibrium carbide-matrix interface, boundaries. results these agreed well results, agreement can be improved by considering effect probe configuration on measurements. calculated data related corrosion behavior alloys. occurrence severe asymmetries some or time, shown due movement during discontinuous precipitation carbides.