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| THE EFFECT OF ALLOYING ELEMENTS ON AGE BRITTLENESS OF A Cr-Mn-C-N AUSTENITIC HEAT-RESISTANT STEEL |
| KUO YUN-YI; LIU CHIA-LO; LI YOU-KO; SHIH CHANG-HSU(Institute of Metal Research; Academia Sinica) |
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Cite this article:
KUO YUN-YI; LIU CHIA-LO; LI YOU-KO; SHIH CHANG-HSU(Institute of Metal Research; Academia Sinica). THE EFFECT OF ALLOYING ELEMENTS ON AGE BRITTLENESS OF A Cr-Mn-C-N AUSTENITIC HEAT-RESISTANT STEEL. Acta Metall Sin, 1964, 7(4): 409-422.
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Abstract It was known that the Cr-Mn-C-N austenitic steels become brittle (a_k<5) after long ageing at the service temperatures. The aim of the present investigation is to examine the effect of the various alloying elements on the age brittleness in a steel with the basic composition of 14% Cr, 17% Mn, 0.3% N and 0.1% C. From the impact tests after ageing up to 2000 hours at 650 and 700℃, it may be concluded that the carbide forming elements as Mo, V, or W deteriorate the toughness of the steel, while B has a beneficial effect.By a combination of electrolytic extraction, X-ray identification, optical and electron microscopic examination, it was found that the ageing embrittlement is caused mainly by the precipitate of carbide and nitride films along the grain boundaries. If the steel contains more than 1% Mo, x and σ phases will appear after ageing for longer periods; whether these intermetallic phases will cause brittleness or not, it depends upon the quantity and distribution of the brittle phases. The addition of boron to this steel will not only retard the precipitation processes but also make the grain boundary precipitate discontinuous, thus improving the toughness after long ageing.
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Received: 18 April 1964
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