Effect of grinding-induced cyclic heating on the hardened layer generation in the plunge grinding of a cylindrical component

• Multi-pass grinding results in a uniform/continuous hardened layer on a cylinder.
• More passes renders a thicker hardened layer and larger compressive residual stress.
• More grinding passes causes a deeper plastic deformation zone with higher hardness.
• Heat accumulation and wheel wear are main causes of hardened layer thickening.
• A too small infeed result in tempering of the hardened layer and a reduced hardness.

This paper discusses the effects of the grinding-induced cyclic heating on the properties of the hardened layer in a plunge cylindrical grinding process on the high strength steel EN26. It was found that a multi-pass grinding brings about a uniform and continuous hardened layer along the circumference of the cylindrical workpiece. An increase of the number of grinding passes, leads to a thicker layer of hardening, a larger compressive residual stress and a deeper plastic deformation zone. Within the plastic deformation zone, the martensitic grains are refined by the thermo-mechanical loading, giving rise to a hardness of 12.5% higher than that from a conventional martensitic transformation. The coupled effects of heat accumulation and wheel wear in the multi-pass grinding are the main causes for the thickening of the hardened layer. A too small infeed per workpiece revolution would result in insufficient grinding heat, and in turn, bring about an undesirable tempered hardened layer and a reduction of its hardness.