The diffusion and solubility of oxygen in solid nickel
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164 kJ/mole'~ 2, ~ )cm/sec 55 kJ/mole~ . ~-~ .]at. pct
(850 to 1400 ~ (800 to 1000 ~
The thermodynamic and transport behaviors of oxygen in solid nickel were fairly well described by a simple quasi-regular model and an interstitial diffusion model, respectively.
I.
INTRODUCTION
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their high temperature strength coupled with resistance to corrosion, nickel and its alloys are becoming increasingly important to high temperature and corrosion applications. Internal oxidation of nickel alloys can increase creep resistance by providing finely dispersed oxide particles I or it can cause deleterious embrittlement, 2 but in either case the diffusivity and solubility of oxygen ih nickel are important parameters to understand the kinetics of the process. The solubility of oxygen in nickel between 600 and 1200 ~ was first reported by Seybolt. 3 His method involved first oxidizing the surface of a pure nickel sheet and then equilibrating the metal and metal oxide in a slightly oxidizing atmosphere. After the superficial oxide layer had been removed, the remaining metallic phase was chemically analyzed for oxygen. Thirty years later Alcock and Browna measured the solubility of oxygen in nickel by a thermogravimetric method. The weight change of a nickel sample was measured as a function of the oxygen fugacity maintained by a CO2/CO gas mixture to determine the terminal solubility. They also roughly estimated the oxygen diffusivity from the time required to reach equilibrium at a particular temperature and oxygen pressure. However, results obtained by both Seybolt3 and Alcock and Brown4 indicated a decrease in the solubility with increasing temperature, in contrast to most metal-oxygen systems. The permeability of oxygen in nickel, i.e., the product of the solubility and the diffusivity, was measured by Smithells and Ransley5 using counter diffusion of oxygen and carbon atoms through the wall of a nickel tube. Values for the oxygen permeability were calculated from the rate of evo-
JONG-WAN PARK, Research Associate, and CARL J. ALTSTETTER, Professor of Physical Metallurgy, are with the Department of Materials Science, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, IL 61801. Manuscript submitted February 4, 1986. METALLURGICALTRANSACTIONS A
lution of carbon monoxide. Oxygen permeability in nickel has been studied using internal oxidation measurements in Ni-Si alloys by Barlow and Grundy 6 in Ni-Cr alloys by Goto, Nomaki, and Koda, 7 and by Stott et al. 8 and in Ni-Be alloys by Lloyd and Martin. 9 To calculate the diffusivity from the permeability, an independent knowledge of the solubility is required. The solubility data of Seybolt 3 for pure nickel were used in the above three internal oxidation works. Smithells and Ransley used a constant value of 0.24 wt pct oxygen. Although there is some agreement between the activation energies obtained by the internal oxidation methods, substitutional-interstitial atom interactions and trapping of interstitial atoms by substitutional solute atoms rend
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