The use of cassava waste to improve the fatigue performance (screening-level) of mild steel

• Cassava petiole waste used as eco-friendly bio-cyaniding agent for mild steel. • Red petioles (Ni/Mn-rich) enhanced pearlite formation and case hardening. • Fatigue life improved up to 757% in treated samples. • Particle size influenced gas release, diffusion depth, and fatigue resistance. • Biomass-based cyaniding offers sustainable alternative to synthetic cyanides This study investigates cassava petiole waste product as a sustainable agent for pack cyaniding of mild steel, focusing on fatigue screening performance. Red (RP) and light green (LGP) petioles of cassava leaves were oven-dried, pulverized, and sieved to 0.3 mm, 0.5 mm, and 1mm particle sizes combined with BaCl 2 , and pack cyanided at 950°C for 2 hours. Elemental enrichment was characterized by atomic absorption spectroscopy (AAS) and spark optical emission spectroscopy (OES). Mechanical and microstructure results were evaluated by screening-level fatigue tests and optical microscopy. All treated samples outperformed the as-received steel. At 677 MPa, the R/1 mm (red petiole) condition achieved 6,000 cycles, exceeding G/1 mm (light green petiole at 3,200 cycles) by 87.5% and the as-received control (700 cycles) by 757% under comparable low stress conditions. From the screening-level effect-size analysis across standardized stresses (828, 1241, 1354 MPa) R/1 mm delivered a 5.9x (+490%) life increases relative to as-received. Although LGP had higher Cr (chromium) and V (vanadium), RP contained more Mn (manganese) and Ni (nickel), which more effectively promoted pearlite formation and deeper case hardening, thereby enhancing fatigue resistance. These results identify cassava petiole biomass—particularly the red variety—as an eco-friendly, cost-effective alternative to conventional cyanide media. The findings emphasize that Mn/Ni-driven microstructural evolution is more decisive than Cr/V enrichment in improving fatigue life in mild steel treated by pack cyaniding.