Papers by Author: Frederick S. Pettit

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Authors: N.M. Yanar, Frederick S. Pettit, Gerald H. Meier
Authors: R.A. Handoko, J.L. Beuth, Gerald H. Meier, Frederick S. Pettit, M.J. Stiger
Authors: N. Birks, Frederick S. Pettit, B. Peterson
Authors: Kee Young Jung, Frederick S. Pettit, Gerald H. Meier
Abstract: When gas turbines use alternate fuels, such as syngas derived from coal, ash from the fuels can deposit on turbine hardware. These deposits can cause substantial corrosion of the hardware which may have significantly different characteristics than Type I and Type II hot corrosion. The composition of the ash is determined by the mineral matter in coals, which often have kaolinite (Al2O3·2SiO2·2H2O), pyrites (FeS2), and calcites (CaCO3) as major components. This study was directed at degradation produced by CaO and CaSO4 and comparing it with the attack induced by Na2SO4 deposits. The alloys GTD 111, IN 738, and René N5, as well as these alloys coated with CoNiCrAlY and platinum aluminide, were exposed to conditions relevant to corrosion induced using alternative fuels. The initial test conditions involved a number of deposits including Na2SO4, CaO, and CaSO4 in dry and wet (pH2O = 10.1 kPa, 0.1 atm) air at 950oC. The most severe degradation occurred with CaO deposits. Specimens of the three alloys were subsequently exposed to cyclic oxidation conditions at 950oC with deposits of CaO in dry and wet air. All three alloys were attacked more severely when CaO deposits were present and this attack became even more severe in wet compared to dry air. However, the increase in attack caused by the presence of water vapor was small compared to the attack caused by the CaO deposits. The degradation induced via CaO deposits caused more severe degradation of René N5 compared to GTD 111 and IN 738. Tests using CaO deposits and cyclic oxidation conditions at 950oC in dry and wet air were also performed for the two coatings on the three alloy substrates. Both coatings were significantly degraded by attack induced by the CaO deposits. No effect of the alloy substrates on coating performance was apparent. Mechanisms for the effects of Ca-rich deposits on superalloy and coating degradation are discussed.
Authors: R.W. Jackson, J.P. Leonard, L. Niewolak, W.Joe Quadakkers, Frederick S. Pettit, Gerald H. Meier
Abstract: In this study, the effects of alloying with Cu and external doping with CeO2 on the oxidation of nickel were evaluated. The materials studied were pure Ni, Ni-5wt% Cu, and Ni with the surface doped with CeO2 by pulsed laser deposition (PLD). The oxidation kinetics were measured using thermogravimetric analysis (TGA). The oxidation microstructures were observed by scanning electron microscopy (SEM) compositional analysis was performed with energy dispersive x-ray analysis (EDS) and sputtered neutrals mass spectrometry (SNMS). Phase identification was performed using X-ray diffraction (XRD). The Cu additions had a negligible effect on the oxidation kinetics but Cu was found to be present in the outer portions of the scale in significant concentrations. Doping with CeO2 resulted in a significant decrease in the NiO growth rate. The scales on doped Ni grew primarily inward whereas those on the undoped Ni grew primarily outward. Deposition of the CeO2 dopant onto Ni with a thin, preformed NiO layer produced a similar reduction in the subsequent NiO growth rate. This suggests that the poisoned interface model, proposed by Pieraggi and Rapp, does not describe the effect of the CeO2 dopant. Mechanisms are presented to attempt to describe the above observations.
Authors: N.M. Yanar, M.J. Stiger, M. Maris-Sida, Frederick S. Pettit, Gerald H. Meier
Authors: S. Sarioglu, J.R. Blachere, Frederick S. Pettit, Gerald H. Meier, James L. Smialek, C. Mennicke
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