Molybdenum and Chromium Depletion at Grain Boundary Precipitates Alloy 926

In this chapter, a mathematical model for rate of formation of chromium carbides near the grain boundary, which is a pre-cursor to chromium depletion and corresponding sensitization behavior in stainless steels, is presented. This model along with the diffusion equation for chromium in the grain has been used to obtain chromium depletion profiles at various time and temperature conditions. Finite difference method has been used to solve the above equations in the spherical co-ordinate system and the results of time-temperature-sensitization diagrams of four different types of alloys have been compared with those of experiment from literature. For the problem of low temperature sensitization and corresponding inter-granular corrosion in austenitic stainless steel, it is very difficult to carry out experiment at higher temperatures and justify its validity at lower operating temperatures by extrapolation. The development of predictive models is highly useful in order to design the structures for prevention of corrosion of the material in aggressive environments.

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On the Role of Grain Size and Carbon Content on the Sensitization and Desensitization Behavior of 301 Austenitic Stainless Steel

Metals ◽

10.3390/met9111193 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1193 ◽

Cited By ~ 1

Author(s):

Kolli ◽

Javaheri ◽

Kömi ◽

Porter

Keyword(s):

Grain Size ◽

Stainless Steel ◽

Austenitic Stainless Steel ◽

Grain Boundary ◽

Carbon Content ◽

Double Loop ◽

Boundary Carbide ◽

Self Healing ◽

Chromium Depletion ◽

Electrochemical Potentiokinetic Reactivation

The effect of grain size in the range 72 to 190 μm and carbon content in the range 0.105–0.073 wt.% on the intergranular corrosion of the austenitic stainless steel 301 has been investigated. Grain boundary chromium depletion has been studied directly using energy dispersive X-ray spectroscopy combined with scanning transmission electron microscopy and indirectly using double loop electrochemical potentiokinetic reactivation tests. In addition, chromium depletion has been modelled using the CALPHAD Thermo-Calc software TC-DICTRA. It is shown that the degree of sensitization measured using the double loop electrochemical potentiokinetic reactivation tests can be successfully predicted with the aid of a depletion parameter based on the modelled chromium depletion profiles for heat treatment times covering both the sensitization and de-sensitization or self-healing. Additionally, along with intergranular M23C6 carbides, intragranular M23C6 and Cr2N nitrides that affect the available Cr for grain boundary carbide precipitation were also observed.

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Intergranular Corrosion Behavior of 00Cr12 Ferritic Stainless Steels Containing Cerium

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.690-693.133 ◽

2013 ◽

Vol 690-693 ◽

pp. 133-138

Author(s):

Ya Bo Li ◽

Fu Ming Wang ◽

Xiao Nong Cheng

Keyword(s):

Grain Boundary ◽

Corrosion Behavior ◽

Stainless Steels ◽

Intergranular Corrosion ◽

Optical Microscope ◽

Mechanism Analysis ◽

Chromium Depletion ◽

Ferritic Stainless Steels ◽

Boundary Density ◽

Grain Sizes

Intergranular corrosion behavior of 00Cr12 ferritic stainless steels with different amounts cerium was evaluated. For this evaluation, electrochemical measurements - polarization curves - were obtained for tested materials, and optical microscope was used to observe corrosive microstructure. Experimental results shows: cerium reduces grain sizes and improves intergranular corrosion resistance of test materials. Through mechanism analysis: cerium reduces grain sizes, increases grain boundary density, therefore might improve distribution aspects of carbides and nitrides, chromium depletion situation near grain boundary would be improved, this work worth further study.

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