Abstract

In machining, titanium alloys are known to have poor machinability due to the combination of various physical properties such as low thermal conductivity, elastic modulus, etc. However, the fundamental reasons behind this poor machinability are not well understood. This talk will present our on-going research being carried out at MSU with a series of turning experiments on various Ti-6Al-4V microstructures in order to identify the root causes for various tool wear phenomenon such as chipping, scoring marks on flank faces and distinct morphologies of crater wear observed on the cutting tools. Confocal laser scanning microscopy, scanning electron microscopy and Orientation Image Microscopy were used to analyze the flank and crater wear of the tools as well as the various microstructures. From the flank wear patterns, two distinct types of damage were identified, (a) microscopic and macroscopic fracture on the cutting edge and (b) scoring marks, which were caused primarily by the heterogeneity in the microstructure. In addition to such heterogeneities, adhesion layer, ubiquitous to machining Ti alloys, detaches small fragments of the tool, which resulted in microscopic and macroscopic fractures observed on flank wear. For crater wear, the evidence of phase transformation is presented and its impact on crater wear is discussed. Both flank and crater wear are affected by interface conditions such as temperature and pressure, which were estimated using finite element analysis (FEA) models. The model-based wear equations are being developed and compared with the experimentally measured wear data.

About the Presenter

Patrick Kwon joined the Department of Materials Science and Mechanics at Michigan State University in 1996, before moving to the Department of Mechanical Engineering in 2001. He received his BSE from University of Michigan (Ann Arbor), SM from MIT and PhD from University of California (Berkeley). His research areas include machining, especially fundamental tool wear mechanisms on ferrous alloys, titanium alloys, CFRP/Ti stack, and compacted graphite iron; lubrication with nano-fluids; and design and powder processing of micro and macro devices including additive manufacturing.