Case study: Wear mechanisms of NiCrVMo-steel and CrB-steel scrap shear blades

Shear blades are extensively used in the recycling of metal scrap. A comparative study was conducted on used medium carbon NiCrVMo and CrB containing steel scrap shear blades to better understand their wear mechanisms under service conditions. The microstructure and hardness of worn cutting edges and bulk material were characterised by optical microscopy, scanning electron microscopy and microanalysis, X-ray diffraction analysis and macro/micro hardness testing. Moreover, tensile and Charpy impact properties were obtained from the bulk material. Several wear mechanisms were identified in both blades which are categorised in two main groups, i.e. spalling and progressive wear. The progressive wear due to abrasive, adhesive and oxidation wear was observed in both blades. In NiCrVMo-steel blades, spalling and crack propagation from surface/subsurface white etching layers mainly caused the severe wear. However, spalling due to delamination wear and crack propagation from severely deformed subsurface layers was the dominant severe wear mechanism in CrB-steel blades.