IMPROVING MACHINABILITY OF HIGH CHROMIUM WEAR-RESISTANT MATERIALS VIA LASER–ASSISTED MACHINING Hongtao Ding and Yung C. Shin Center for Laser-Based Manufacturing, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA & The machinability of high chromium wear resistant materials is poor due to their high hardness with a large amount of hard chromium carbides. This study is focused on improving the machin- ability of high chromium wear resistant materials with different microstructures and hardness levels via laser-assisted machining (LAM). A laser pre-scan process is designed to preheat the work- piece before LAM to overcome the laser power constraint. A transient, three-dimensional LAM ther- mal model is expanded to include the laser pre-scan process, and is validated through experiments using an infrared camera. The machinability of highly alloyed wear resistant materials of 27% and 35% chromium content is evaluated in terms of tool wear, cutting forces, and surface integrity through LAM experiments using cubic boron nitride (CBN) tools. With increasing material removal temperature from room temperature to 400  C, the benefit of LAM is demonstrated by 28% decrease in specific cutting energy, 50% improvement in surface roughness and a 100% increase in CBN tool life over conventional machining. Keywords high chromium wear resistant materials, laser-assisted machining, surface integrity, tool wear INTRODUCTION High chromium cast irons are white cast irons alloyed with 12 to 35% chromium and generally fall into a category defined by ASTM A 532 standard (Lampman and Zorc, 1990). These materials are commonly used for materials handling in the mining and minerals processing industries because of their exceptional wear resistance, which is a result of the large volume fraction of primary and=or eutectic chromium carbides in their microstructures (Lampman and Zorc, 1990; Tabrett et al., 1996). For Address correspondence to Yung C. Shin, Center for Laser-Based Manufacturing, School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA. E-mail: shin@purdue.edu Machining Science and Technology , 17:246–269 Copyright # 2013 Taylor & Francis Group, LLC ISSN: 1091-0344 print=1532-2483 online DOI: 10.1080/10910344.2013.780549 Downloaded by [Purdue University] at 12:57 06 May 2013