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  • P-ISSN 1225-0163
  • E-ISSN 2288-8985

Measurement of the Phase Fraction of Minor Precipitates in Ni Base Superalloys using Quantitative X-ray Diffraction Technique

Analytical Science and Technology / Analytical Science and Technology, (P)1225-0163; (E)2288-8985
1999, v.12 no.3, pp.235-242
Kim, S.E.
Cho, C.C.
Hur, B.Y.
Na, Y.S.
Park, N.K.
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Abstract

It is impossible to measure the fraction of the precipitates which are neither plenty nor distiguishable on micrographs, using point counting method or image analyzer. In this study, phase fraction of sigma, carbide and boride which are important to mechanical properties of Ni base superalloy Udimet 720 has been measured using a quantitative X-ray diffraction technique combined with electrochemical extraction. The alloys had been exposed at <TEX>$800^{\circ}C$</TEX> for various times up to 3000 hours to have a variation of the amount of the minor precipitates. The amount of sigma had increased exponentially with increasing exposure time up to 3000 hours before saturation. It can be argued that the finishing point of precipitation is around 5000 hours and maximum amount of sigma to be produced is about 5% in weight. The amounts of <TEX>$M_{23}C_6$</TEX> and <TEX>$M_3B_2$</TEX> were maintained constant at the level of 0.1~0.5% in weight, regardless of exposure time.

keywords
Ni-base superalloy, Udimet 720, Sigma phase, Electrolytic extraction, Quantitative X-ray diffraction


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