Abstract
NiCoCrAl/WC + (1–4) wt.% La₂O₃ coatings were cladded on H13 tool steel using Nd: YAG pulsed laser. Scanning electron microscopy, wavelength dispersive X-ray spectroscopy, electron probe microanalysis, and X-ray diffraction are used to study the coatings and oxide layers. The oxidation kinetics analysis of coatings at 700 °C in a static air atmosphere shows that the oxidation of coatings with La₂O₃ slows down or stops while a compact and stable oxide layer is formed. The formation of NiCr₂O₄ spinel makes the oxide layer compact and blocks the connection paths connecting the coating/oxidizing environment. A study of the oxidation mechanism revealed that in coatings with La₂O₃, short-path diffusion has been preferred due to a fine dendritic microstructure and sufficient opportunity to form NiCr₂O₄ spinel. Addition of up to 2 wt.% La₂O₃ makes the coatings effectively resist oxidation. An equation has been derived for the oxidation kinetics using the data analyzed with Python^TM software.

Key words
kinetics of oxidation, laser cladding, composite coating, high temperature, isothermal oxidation

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