Comparative Study of AlSi10Mg and 304 Stainless-Steel Fillers in PA12 Composites Manufactured Using Injection Moulding Process for Liners and Sleeve-Based Applications: Microstructure, Mechanical Properties, Thermal Stability, and Wear Behaviour

This study presents a comparative evaluation of injection-moulded PA12 composites reinforced with AlSi10Mg and 304 SS fillers, with emphasis on microstructure-property correlations linking powder morphology, mechanical performance, thermal stability, and tribological behaviour. Powder characterization revealed distinct morphologies-fine spherical AlSi10Mg particles (D50 ≈ 32 µm) dispersed uniformly in the matrix-while SS particles (D50 ≈ 245 µm) tended to agglomerate, leading to interfacial voids. Tensile testing showed that the elastic modulus of neat PA12 (0.95 GPa) increased by 20% and 28% with 20 wt% AlSi10Mg and SS, respectively. However, tensile strength decreased from 35.04 MPa (PA12) to 32.18 MPa (20 wt% AlSi10Mg) and 31.03 MPa (20 wt% 304 SS), consistent with stress concentrations around particle clusters. Hardness values remained nearly unchanged at 96-98 Shore D across all composites. Thermal analysis indicated that AlSi10Mg promoted crystallization, increasing crystallinity from 31% (PA12) to 34% and raising Tm by 2 °C. In contrast, 304 SS reduced crystallinity to 28% but significantly improved thermal stability, shifting Tonset from 405 °C (PA12) to 426 °C at 20 wt%. Tribological tests demonstrated substantial improvements: the coefficient of friction decreased from 0.42 (PA12) to 0.34 (AlSi10Mg) and 0.29 (304 SS), while wear rates dropped by 40% and 55%, respectively. SEM confirmed smoother worn surfaces in AlSi10Mg composites and abrasive grooves in 304 SS composites. The findings show that AlSi10Mg is advantageous for smoother surfaces and improved crystallinity, while SS enhances stiffness, wear resistance, and thermal endurance, providing design guidelines for PA12 composites in aerospace, automotive, and engineering applications.