Studies on Dry Sliding Wear Mechanisms of Al7075/Si₃N₄ Composites

In this investigation, Al7075 aluminum alloy reinforced with Si₃N₄ particles (3, 6, 9, and 12 wt%) was used as reinforcements to manufacture composites through a stir-casting approach. The microstructural characteristics have shown significant grain refinement owing to the presence of Si₃N₄ particle distribution during the solidification. SEM micrographs confirm the uniform distribution of Si₃N₄ particles with considerably fewer particle agglomerations throughout the matrix alloy. The reinforcement particle cluster formation is relatively increased for increasing the Si₃N₄ content. The SEM and EDS analyses showed good integrity at the matrix–refinement interface with no interfacial compound formation. The mechanical properties, such as hardness (up to 118 BHN), tensile strength (up to 281 MPa), and yield strength (up to 178 MPa), were enhanced by 30.69% and 20.27%, respectively. The wear-rate and coefficient of friction of the composites were evaluated with increasing percentages of Si₃N₄ content. The average wear-rate of the composites is 0.019, 0.0085, 0.0075, and 0.0065 mm³/m, respectively, for the increased Si₃N₄ ceramic particulate content from 3 to 12 wt%, while the average COF of the composites is 0.45, 0.37, 0.32 and 0.28 respectively. With the addition of Si₃N₄ particulate content, the wear resistance performance of the composites at 30 N has shown up to 46% enhancement and increased from 0.0052 to 0.0103 mm³/m with the increasing sliding velocity from 1.5 to 3.5 m/s for varying Si₃N₄ particulate content from 3 to 12 wt%, while reducing the COF up to 65%, and from 0.43 to 0.27. Different wear mechanisms are characterized by identifying the typical features of wear on the SEM micrographs of the worn surfaces. The dominant wear mechanisms of the composites are typically observed as abrasion, oxidation, delamination and melt wear. The mechanism and behavior of composites under dry sliding conditions are analyzed through the construction of wear maps. The windows of wear mechanisms and progression in terms of load and sliding velocity for the composites with various wt% of Si₃N₄ content were identified, analyzed, and presented.