Influence of Mo content on the phase evolution and corrosion behavior of model Fe–9Cr–xMo (x = 5, 7, and 9 wt%) alloys

Abstract

Model Fe-9Cr-xMo alloys with high Mo content alloys were cast to investigate the effect of Mo on the phase evolution and properties of the alloys. The Mo contents in the alloys were 5, 7, and 9 wt%, while the Cr content was held constant at 9 wt%. For comparison, a commercial A213T 9-P9 (Fe-9Cr-1Mo) alloy, widely used in the petrochemical industry, was also investigated. The alloys were heat-treated at temperatures between 450 and 650°C and characterized by scanning electron microscopy, x-ray dispersive energy spectroscopy, and electron backscatter diffraction. Potentiodynamic linear polarization technique was used to evaluate the corrosion of the alloys in a 0.5 mol L À1 H 2 SO 4 solution containing 0.1 mol L À1 NaCl. The results showed that the corrosion resistance of the alloys was affected by precipitation of the l phase and that the Mo content in excess of 5% is deleterious to the corrosion resistance of the Fe-Cr-Mo alloys.

Embrittlement and aging at 475 °C in an experimental superferritic stainless steel with high molybdenum content

“…It was observed that annealed samples pitting potentials (E p ) for 7Mo4Ni (E p = 1,06 V) and 7Mo2Ni (E p = 1,04 V) were greater than for 5Mo4Ni (E p = 1,03 V), probably due to the higher Mo content in these alloys. The increase Mo content in the FeCrMo alloys improve corrosion resistance in various environments [10][11][12].…”

“…The increase in the performance of ferritic stainless steels is achieved with levels of Cr above 25% and Mo additions. Studies have been published that Mo addition improves corrosion resistance in various corrosive environments including naphthenic acid corrosion that results from the processing of heavy crude oil [8][9][10][11][12]. The low levels of C and N improve the ductility and corrosion resistance, and allow the addition of Ni to improve the toughness.…”