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Nitriding and fatigue resistance

2004

Dear Friends:

I am interested in improving the high cycle fatigue life of 4340QT steel shafts. I understand that the fatigue life can be improved through gas nitriding. But, I have a few questions re this nitriding. I am looking for published articles that describe: (i) the formation of the white layer and alloy layer, (ii) the Young's Modulus and Poisson's ratio of the nitride and alloy layers, (iii) the influence of white layer on high cycle fatigue, and (iv) does the nitride layer thickness influence fatigue life.

Thanks,

Henry Higgins
research - Cleveland, Ohio

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Nitriding is a popular surface hardening process, which means that you will be able to find a great deal of information in the form of published technical articles, books, etc. The two best references for information on the process are ASM Metals Handbook Vol. 4 'Heat Treating' [affil link on Amazon] and Practical Nitriding and Ferritic Nitrocarburizing [affil link on Amazon] by D. Pye, both published by ASM INTERNATIONAL. You can obtain them from the ASM online bookstore.

Other good sources of information are nitriding vendors. Both Nitrex and the Contract Heat Treatment Association from the UK have information available on their websites. Ovako Steel has an excellent report on nitriding called "Properties of Nitrided Components - A Result of the Material and the Nitriding Process" that is available from their website as well.

For a more fundamental search of the available scientific literature, I suggest performing a search using Cambridge Scientific Abstracts or Elsevier's Scirus. The former has a regular publication that lists all of the articles published on nitriding titled "Nitriding Techniques for the Hardening of Steels".

Toby Padfield
Automotive module supplier - Michigan
2004