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Abstract:A comparative study of the microstructure, hardness, and tribological properties of two different AISI H13 tool steels-classified as the bulk with no heat treatment steel or the 3D-printed steel-was undertaken. Both samples were subjected to ultrasonic nanocrystalline surface modification (UNSM) to further enhance their mechanical properties and improve their tribological behavior. The objective of this study was to compare the mechanical properties and tribological behavior of these tool steels since steel can exhibit a wide variety of mechanical properties depending on different manufacturing processes. The surface hardness of the samples was measured using a micro-Vickers hardness tester. The hardness of the 3D-printed AISI H13 tool steel was found to be much higher than that of the bulk one. The surface morphology of the samples was characterized by electron backscattered diffraction (EBSD) in order to analyze the grain size and number of fractions with respect to the misorientation angle. The results revealed that the grain size of the 3D-printed AISI H13 tool steel was less than 0.5 µm, whereas that of the bulk tool steel was greater than 4 µm. The number of fractions of the bulk tool steel was about 0.5 µm at a low misorientation angle, and it decreased gradually with increasing misorientation angle. The low-angle grain boundary (LAGB) and high-angle grain boundary (HAGB) of the bulk sample were about 21% and 79%, respectively, and those of the 3D-printed sample were about 8% and 92%, respectively. Moreover, the friction and wear behavior of the UNSM-treated AISI H13 tool steel specimen was better than those of the untreated one. This study demonstrated the capability of 3D-printed AISI H13 tool steel to exhibit excellent mechanical and tribological properties for industrial applications.

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“Glass wool” and “rock wool” had been used as sound absorbing materials over several decades because they have excellent sound absorbing properties as well as being very productive and economical. Unfortunately, they were found to be toxic because of flying glass whiskers. To replace glass wool and rock wool as the sound absorbing panels, the recycled glass powders with zeolite and Na2SiO were foamed, adding foaming agents such as NaOH and CaCO3 at different foaming temperatures and time in an electrical furnace. Recycled glass powders from crushed passenger car window were heated up to 720°C in an electrical furnace for an optimal foaming condition. The compressive strength of the foamed glasses was measured using a dynamic materials tester. On the basis of microstructure observation of the foamed glasses, the excellent sound absorbing materials was tried to be fabricated by measuring the sound absorbing coefficient of the foamed glass materials by adding various amounts of NaOH and water.

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