Effect of carbon nanotubes intensified coolant on the grinding performance of carburizing and quenching 12Cr2Ni4A steel

Abstract

12Cr2Ni4A steel is a high-quality alloy structural steel. This article explores the surface/sub-surface condition, surface roughness, and micromorphology of the workpiece surface after grinding 12Cr2Ni4A steel via nanofluid casting to characterize the surface quality and analyzes the burn condition of the workpiece based on the microhardness of the cross-section of the workpiece and the micro-morphology of the subsurface of the workpiece. The test results indicate that the high heat transfer capacity of the carbon nanotube nanofluid can prevent the workpiece from being burned; further, the nanofluid casting type grinding obtains the lowest grinding force and surface roughness compared to the normal and tangential grinding forces. The surface roughness is reduced by 19.2%, 25.0%, and 19.1% at the highest because the nanoparticles (carbon nanotubes) play a "lubricating effect" in the grinding area, and the surface quality of the workpiece is therefore improved. The microhardness of the cross-section of the workpiece indicates that a softened layer appears on the workpiece after dry grinding at normal temperature and on the workpiece after traditional casting grinding. The maximum softening layer thickness for normal temperature dry grinding and traditional casting grinding is ~100 and 40 µm, respectively; no obvious softening layer was observed in nanofluid casting grinding. Tempering burns and secondary quenching burns appear on the subsurface of the workpieces of normal temperature dry grinding and traditional casting grinding. The thicknesses of the affected layers of the tempering and secondary quenching burns are ~98 and 35 µm, respectively; for the nanofluid casting, no obvious burns were observed on the sub-surface of the workpiece ground by type grinding. Thus, this research aims to explore how to minimize grinding burns and propose a new type of nanofluid casting grinding technology.