Full definition
Impact wear refers to the material loss that occurs when particles repeatedly strike a surface at moderate to high angles, typically greater than 45°. This phenomenon is particularly prevalent in various mining operations, such as conveyor loading zones, crusher discharge points, cyclone feeds, and mill discharge areas. Unlike traditional wear mechanisms where hardness is the key factor, impact wear emphasizes resilience—the capacity of a material to absorb and elastically return from impact energy. For instance, natural rubber (NR) exhibits a resilience of approximately 80%, significantly outperforming hardened steel, which has a resilience of less than 5%. This striking difference highlights why NR is often preferred in environments subject to impact wear, as it can absorb kinetic energy without significant material loss, while steel may suffer from plastic deformation and micro-cutting upon impact.
The optimal hardness for natural rubber used in impact wear applications typically ranges from 35 to 55 Shore A. Softer compounds, while effective at absorbing energy, may be prone to tearing, whereas harder compounds tend to lose their resilience, making them less effective in high-impact scenarios. This balance is crucial in applications such as transfer chute linings and hopper impact zones where the forces involved can be quite significant. In cases where both impact and sliding abrasion are present, such as in conveyor systems, rubber-backed ceramic composite tiles offer an effective solution. The ceramic layer resists sliding abrasion, while the rubber backing mitigates the effects of impact, providing a comprehensive approach to wear protection.
Testing for impact wear can be supplemented by erosion testing methods such as ASTM G76, which evaluates material performance under specified conditions. Additionally, field wear rates can be measured in millimeters per year or millimeters per 1000 hours of operation to assess the effectiveness of materials used in high-impact environments. Understanding the dynamics of impact wear is essential for engineers and maintenance professionals in order to select the right materials and designs to minimize wear and extend the lifespan of equipment in mining operations.