Abstract
Abstract
Paralinear oxidative behavior, i.e., concurrent parabolic scale growth (kp) and linear scale volatility (kl or kv), was analyzed by an alternative to the Tedmon equation. A convenient COSP for Windows cyclic oxidation program analyzed published data for Cr, NiCr, Pb, SiC, Si3N4, and BN, all exhibiting scale volatility due to CrO3, CrO(OH)2, PbCl2, Si(OH)4, and HBO2. The ‘cyclic’ model used an iterative constant outer layer loss formalism, whereby a normalized spall constant, Q0 /Δt, defines the scale volatility rate, kl (or kv). Optimized trial inputs (fitting maximum mass gain (ΔWmax, tmax) and time to cross zero) generated accurate kp and kl and replicated ideal paralinear form. Initial approximations for kp and kl can now be obtained directly as ~ 4.1 (ΔWmax2/ tmax) and ~ 1.2 (ΔWmax / tmax), respectively. However, high or low kl extremes, (e.g., burner rig tests of SiC and Ti2AlC), may elude classic paralinear behavior. Inconsistencies between Tedmon’s stated model parameters and actual data are also discussed.
Publisher
Research Square Platform LLC
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