Granular flows exert significant erosion on erodible beds during movement, yet the dynamic and energy conversion mechanisms underlying particle erosion remain inadequately understood. This study investigates the erosion mechanisms induced by granular flows through controlled indoor flume experiments. By varying the properties of the erodible layer, comprising clay, sand, and sand-clay mixtures, the study examines their impact on the erosive force and dynamics of the flows. The findings highlight the crucial role of terrain changes within the erosion zone, with different materials showing notable differences in erosion depth and force. Clay exhibited the greatest influence on flowability, demonstrating higher erosive shear force and depth compared to sand and sand-clay mixtures. Additionally, the study compared measured erosive forces with those predicted by the Coulomb and Voellmy models, revealing that the Coulomb model underestimated, while the Voellmy model overestimated, both the erosion force and depth. A novel block energy model was proposed to elucidate the energy evolution during the erosion process, identifying a critical relationship that explains why some erosive granular flows exhibit increased mobility while others do not. This work advances the understanding of granular flow erosion mechanisms from an energy perspective.