Optimization of friction stir processing parameters for mechanical properties and sliding wear characteristics of marble dust reinforced AA7075 alloy surface composites

In this study, friction stir processing (FSP) of AA7075 alloy reinforced with waste marble dust (MD) was conducted with varying A: tool rotational speed (700, 1000, 1400 and 2000 rpm), B: tool feed rate (14, 20, 28, and 40 mm/min), C: tool pin profile (circular, conical, pentagon and hexagon) and D: MD particle size (50, 100, 150 200 μm) to develop surface composites. The experiments and optimization of FSP control factor combinations were designed using an L16 orthogonal array of Taguchi design. The developed surface composites were tested based on micro-hardness, tensile strength, impact strength and sliding wear characteristics. The findings show that A: tool rotational speed and D: MD particle size have the most significant effect on mechanical and sliding wear characteristics. The best set of FSP control factors, i.e. 2000 rpm tool rotational speed (A4), 20 mm/min tool feed rate (B2), pentagon tool pin profile (C3), and 50 μm MD particle size (D1), provides the best mechanical characteristics. Moreover, increased tool rotational speed produced a notable decrease in specific wear rate with increasing sliding distance, showing a positive response as a result of better material flow and dispersing of MD particles. The research shows that a proper choice of the FSP control factors can significantly improve the surface integrity and durability of the surface composite of AA7075 alloy reinforced with MD. The results offer an economical and durable solution to the development of high-performance surface composites to be used in engineering applications where a superior sliding wear resistance and mechanical characteristics are needed.