ISSN:
1573-4889
Keywords:
INTERNAL NITRIDATION
;
NITROGEN DIFFUSION
;
NITROGEN SOLUBILITY
;
FINITE-DIFFERENCE TECHNIQUE
;
THERMODYNAMIC EQUILIBRIUM CALCULATIONS
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Whereas in Part I of this study the process ofinternal nitridation was described for binary andternary alloys within the Ni-Cr-Al-Ti system, this partfocuses on quaternary Ni-Cr-Al-Ti alloys, which are similar to commercial Ni-base alloys used inhigh-temperature applications regarding their chemicalcompositions. These alloys can simultaneously form twodifferent nitride-precipitation zones consisting of TiN and AlN. In order to quantify thenitridation process, thermogravimetric measurements inan oxygen-free nitrogen atmosphere in the temperaturerange 800-1100°C were carried out and supplemented by extensive microstructural studies. Whilesingle-nitride internal nitridation can easily bedescribed by Wagner's theory of internal oxidation,modeling of the more complex internal-precipitationreactions that involves more than one nitride requires anumerical treatment of both the diffusion and thethermochemical processes in the alloy. For this purpose,a computer simulation was developed in which the commercial thermodynamic software ChemApp iscombined with a finite-difference diffusion calculation.It was shown that this calculation technique can beapplied successfully to quantitatively describe the internal-nitridation process of theNi-Cr-Al-Ti model alloys used in this study.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018895628849
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