Fe-33Ni-19Cr alloy is the Ni-based alloy used at high temperature condition due to its excellent ability to form protective oxide layer at high temperature. Fe-33Ni-19Cr alloy was undergo a series of solution treatment process to vary the grain size of the alloy. The Fe-33Ni-19Cr alloy was solution-treated at 3 different temperature, namely 1000°C, 1100°C and 1200°C, for 3 hours soaking time, followed by water quench. The solution-treated alloys were then experienced an isothermal oxidation test at 900°C for 500 hours in laboratory air. The oxidized Fe-33Ni-19Cr alloy were characterized in terms of phase analysis and cross-sectional analysis using XRD and SEM-EDX to investigated the effect of different grain size alloy to the oxidation behavior. The solution treatment process was produced varies grain size of Fe-33Ni-19Cr alloy. The solution-treated Fe-33Ni-19Cr alloy at 1000°C exhibited the fine grain size, while solution-treated Fe-33Ni-19Cr alloy at 1200°C produced a coarse grain size. The oxidized Fe-33Ni-19Cr alloy recorded a formation of several oxide phases consists of Cr-rich oxide, Fe-rich oxide, Ti-rich oxide and spinel oxides structure. The cross-sectional analysis displays a several layer of oxide scales formed on the alloy surface with evidence of internal oxide penetration through the grain boundary area.

Fruit skins are waste and natural fibers which are processed from it can be used as filler material in polymer composites. These natural fibers are surely inexpensive, non-toxic and environmentally friendly. In the other hand, natural fibers are chemically hydrophilic and absorb water. Their nature which are rich cellulose making it hydrophilic in nature. Besides their nature to water, the ability of natural fibers to absorb oil also interesting to be studied. In this paper, natural fibers from several types of fruit skin were used as filler in thermoplastic polyurethane (TPU) composites. The fibers from pineapple skin, coconut shell, coconut husk, corn cob, rambutan, mangoesteen and banana with the percentage of 15% and 20% were incorporated with TPU through melt mixing technique. Every type of natural fiber will absorb oil and water at different rate, as well as the effect of filler content in the composite. Overall, the absorption of water and oil increased its percentage when the filler content increases. Rambutan, pineapple and banana absorb more water than others at 20% filler content in the TPU. Pineapple and rambutan also tend to absorb more engine oil.

The isothermal oxidation test has been investigated on two types of Fe-Ni-Cr alloy, namely Fe-33Ni-19Cr and Fe-40Ni-24Cr alloys. Both alloys were undergoing an isothermal oxidation test at temperature of 500? for 500 hours exposure time. The weight change per surface area of the oxidized samples has been recorded to calculate the oxidation kinetics of both alloys. The oxide growth behaviour of oxidized samples has been examined using scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) spectrometer. The oxide phase formed on the sample surface has been analyzed using x-ray diffraction (XRD) technique. The results show that both alloys were followed a parabolic rate law, indicating a diffusion-controlled oxide growth mechanism. In addition, the oxidation kinetics indicating an increasing weight gain trend as the exposure time increase. Several oxide phases had formed on the oxidized surface of both alloys, consists of Cr-rich, Ti-rich, Fe-rich and spinel oxide structure. The surface morphology of both alloys demonstrated a continuous oxide scale formed on the alloy surface. Additionally, Fe-33Ni-19Cr alloy recorded a formation of Ti-rich oxide, whereas, Fe-40Ni-24Cr alloy displayed a formation of overgrown Nb-rich oxide particle which. Roles of the precipitates in oxidation mechanism give new insights into the alloy optimization.

The isothermal oxidation behavior of two different grain size of Fe-33Ni-19Cr alloys was investigated at 700 °C in laboratory air. Different grain size of alloyed was made of solution annealing treatment at different temperatures, namely, 1050 °C and 1150 °C for fine and coarse grain, respectively. Optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were employed in this study to analyze the oxidation behavior of solution-annealed samples. Results indicate that the fine grain size solution-annealed alloys possess a better oxidation resistance and reduced oxidation rate than the coarse grain. The differences observed are attributed to the finer grains increasing the relaxation of the oxide scale stress and improving the adhesion of the oxide layer on the matrix.

The effect of surface preparation on the isothermal oxidation behavior of Fe-33Ni-19Cr alloy was study in this paper. The surface preparation of the test samples was obtained by grinding process using different grit of silicon carbide abrasive paper, namely P600, P800 and P1000. The surface area and weight of the sample were measured before the oxidation test, by using Vernier caliper and analytical balance. The ground sample of Fe-33Ni-19Cr alloys were isothermally oxidized at 1000℃ for 150 hours in laboratory air. The weight of oxidized samples was recorded after the isothermal oxidation test at every 25 hours exposure duration in order to determine the oxidation kinetic of all samples. The oxide surface morphology of Fe-33Ni-19Cr alloy was characterized by scanning electron microscope. The oxidation kinetic of all samples displayed a weight gain pattern as the exposure duration increase, followed a parabolic rate law. While the result of surface morphology shows that the lowest grit of surface finish, P600, display less oxide exfoliation occurred.