Wear development on wiper Al_2O_3-TiC mixed ceramic tools in hard machining of high strength steel

摘要

This paper explores the wear mechanisms occurring for the mixed ceramic inserts against 60 HRC alloy steel (equivalent to AISI5140 or DIN 41Cr4) specimens in dry and hard finish turning operations. Several machining wear tests were performed under varying feed rate, constant cutting speed of 100 m/min and small depth of cut of 0.2 mm. Light optical microscopy (LOM), scanning electron microscopy (SEM) and back-scattering electron (BSE) technique were employed to observe morphological features of worn surfaces produced by various wear mechanisms. In addition, the elemental compositions of wear products were evaluated by energy-dispersive X-ray (EDX) micro-analysis, called sometimes energy-dispersive X-ray spectroscopy (EDS). As a result, both microscopic and microstructural aspects of ceramic tool wear were considered. In general, wear mechanisms identified in the machining tests involve abrasion, fracture, plastic flow and transferred layers, BUE and tribochemical effects. Specific wear symptoms appeared depending on the mechanical and thermal conditions generated in the wear zones. In particular, two types of material transfer with different morphologies occurring at the rake-chip interface are distinguished.