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E ect of Heat Treatment and Composition on Electrochemical Behaviour of AISI 420 Martensitic Stainless Steels

Meer, S.R.H. van der (2016) E ect of Heat Treatment and Composition on Electrochemical Behaviour of AISI 420 Martensitic Stainless Steels. Master's Thesis / Essay, Applied Physics.

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Abstract

In this research the effect of hardening and tempering temperature, time and environment is studied with use of electrochemical experiments, microscopy and spectroscopy. In this way influence of parameters like, temperature, time, environment and composition on the corrosion resistance could be measured and used to model the AISI 420 martensitic stainless steel. It was found that increasing the tempering temperature decreases the pitting potential due to an increase of carbide formation. By tempering in air surface oxides were grown. For tempering at 250 °C iron oxides are formed on top of the metal surface, which are lowering the current density and affecting the pitting potential. By increasing the tempering time the pitting potential E pitt decreased. Growing chromium oxides by tempering in vacuum at 600 °C the passive behaviour was diminished. The alloying elements nickel and molybdenum stabilize the passive layer but therefore do not effect the pitting potential. Niobium is involved in different mechanisms during the heating stages and increased the OCP but lowered the pitting potential E pitt. Polishing the samples down to 0,25 micron also diminished the passive behaviour during polarization tests, this seems to be caused by a damaged surface after the polishing before testing.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Applied Physics
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:30
Last Modified: 15 Feb 2018 08:30
URI: http://fse.studenttheses.ub.rug.nl/id/eprint/15600

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