A Survey on the Oxidation Behavior of a Nickel-Based Alloy Used in Natural Gas Engine Exhaust Valve Seats

This study reports the oxidation behavior of a Ni-based alloy used in manufacture valve seats for automotive engine exhaust systems. Isothermal thermogravimetric analyses were carried out at temperatures 660, 740, 860, and 900 °C under an oxygen atmosphere up to 1 h. At 660 740 °C, only one stage was observed during whole time studied. this stage, oxide layer formed mainly by NiO + Cr2O3, following linear law with rate constant (Kl) on order magnitude 10−6 kg/m2s apparent activation energy (Ea) ~47 kJ/mol. 860 identical first transition different stage. In second composed parabolic followed (Kp) 10−8 kg2/m4s Ea ~128 Moreover, dense compact after oxidation, no cavities, pores, or microcracks. Characterization techniques such as Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared (FTIR), Raman characterize layer.