Wear and Friction Behavior of in-situ AA5052/ZrB2Composites under Dry Sliding Conditions

In-situ AA5052/ZrB2 composites with different volume percentage (0,3, 6 and 9 vol.%) of zirconium diboride (ZrB2) particles were successfully prepared by in-situ reaction between two inorganic salts potassium-hexa-fluoro-zirconate (K2ZrF6), potassium tetra-fluoro-borate (KBF4) and aluminum alloy AA5052 at 860 °C. The composites were characterized by X-ray diffractometer (XRD) for the confirmation of in-situ formed ZrB2 particles. Optical microscopy examination reveals the grain refinement of Al-rich grains due to in-situ formed ZrB2 particles. Scanning electron microscope (SEM) and Energy dispersive X-ray spectroscopy (EDS) studies were carried out to reveal the morphology, distribution and secondary confirmation of ZrB2 particles in the matrix. Transmission electron microscope (TEM) analysis was done to reveal the crystal structure, interfacial characteristics and dislocations around the ZrB2 particles. Hardness of composites improved significantly as compared to base alloy. Dry sliding wear and friction study of composites was carried out at room temperature on pin-on-disc apparatus. The results revealed that cumulative weight loss of both the base alloy and composites shows a linear relationship with sliding distance, however, change in slope is observed at certain intervals. Wear rate decrease with formation of in-situ ZrB2 particles and improves as the reinforcement amount increases, whereas, coefficient of friction of composites follows a reverse trend. Worn surfaces of pin samples reveal mild-oxidative and severe-metallic wear under scanning electron microscope.