Wear model in turning of hardened steel with PCBN tool José C. Camargo a,1 , Dany Sanchez Dominguez a,1 , Emmanuel O. Ezugwu b , Álisson R. Machado c, ⁎ a Laboratory for Manufacturing, School of Mechanical Engineering, State University of Santa Cruz, Campus Soane Nazaré de Andrade, km 16, Rodovia Jorge Amado, CEP: 45662-900, Ilhéus, Bahia, Brazil b Air Force Institute of Technology, Nigerian Air Force Base, Kaduna, Nigeria c Laboratory for Teaching and Research in Machining, School of Mechanical Engineering, Federal University of Uberlandia, Av. João Naves de Ávila, 2121, Minas Gerais, CEP: 38408-100, Brazil abstract article info Article history: Received 2 April 2014 Accepted 28 June 2014 Available online 5 July 2014 Keywords: Tool wear model AISI D6 steel PCBN tool Hard turning In this study a mathematical–computational model of tool wear of PCBN (polycrystalline cubic boron nitride) was developed in turning of quenched and tempered AISI D6 steel (57 HRC) using experimental planning and statistic techniques. On the experimental trials many parameters are important such as: surface roughness, cutting force and tool wear. These parameters were evaluated according to their statistical significance using Statistica ® and Matlab ® softwares. Through a multiple-regression analysis, it was possible to establish a mathematical model for estimating tool wear as a function of the cutting parameters. This model enhanced estimation of the ideal cutting conditions for turning hardened steel, i.e., those that generate minimum damage on the PCBN tool without compromising productivity. © 2014 Elsevier Ltd. All rights reserved. Introduction Cold work tool steels are consistently gaining more importance in several engineering applications, especially in components requiring high toughness and resistance to wear, appropriate balance of mechan- ical and metallurgical properties and good corrosion resistance [1,2]. These steels are primarily used to fabricate dies and tools used in cold processing of other steels, cast irons and nonferrous metals, in a various manufacturing operations such as cutting, stamping, coining, extrusion, drawing of steel, wood work, pressing of metallic and ceramic powders, milling of pigment inks, rock drilling and paper cutting [3]. One of the main characteristics of these steels is the susceptibility to quenching heat treatment to obtain very high hardness (56–62 HRC). Normally, machining of materials with hardness exceeding 45 HRC is designated as hard machining [4], and turning is the typical operation employed. Until recently, materials that needed to be machined in their hardened condition and to meet surface finish and dimensional accura- cy requirements were traditionally machined by abrasive processes such as grinding. Recent improvements in machine tool technology (specifically the rigidity and positioning accuracy) and the advent of ceramic and ultra-hard tool materials such as PCBN (polycrystalline cubic boron nitride) ensured finish machining of hardened steels using a process with defined tool geometry such as turning [5]. Gener- ally grinding is the operation used for finishing processes because the manufacturing technology of ceramic grinding wheels is well established and has dominated since the 1970s. Tools for machining with defined geometry that were made from ceramic materials had, until the recent past, encountered problems of brittleness which adversely affected their useful life. Today's market offers tools with better qualities, but their economic viability are limited to machining of materials with hardness below 300 HV. For materials with higher hardness, the ultra-hard compounds of boron nitride are recommended [1]. For most applications the grinding operation has a material removal rate lower than the machining processes employing cutting tools with defined geometry [6]. Thus, whenever possible, it is desirable that the grinding process is replaced by hard turning opera- tion. The advantages presented by hard turning are very attractive for companies, but they are still reluctant to replace a well-known and mastered finishing operation (grinding) by a process that is not yet consolidated. This is because universal acceptance of this process of machining these steels (with high hardness) demands special machines and cutting tools with high rigidity and accuracy [7]. This is why the hardened steels are often referred to as complex materials. Normally, machining of hard materials with PCBN tools are carried out at higher speed and feed conditions to generate longer tool life [8]. The need to provide useful information about the influence and the correlation between the machining parameters e.g. cutting speed, feed rate, depth of cut and tool geometry on tool wear was the primary motivation for this study. In the current context where tool steels for cold work operations are widely used, the development of technology for their machining becomes a relevant factor for the generation of knowledge and also a competitive alternative. The characteristics and strategy employed in the machining of tool steel for cold work AISI/ABNT D6 were investigated. The machinability was evaluated in Int. Journal of Refractory Metals and Hard Materials 47 (2014) 61–70 ⁎ Corresponding author. Tel.: +55 3432394148; fax: +55 3432394206. E-mail addresses: jccamargo@uesc.br (J.C. Camargo), dany@labbi.uesc.br (D.S. Dominguez), eoezugwu@gmail.com (E.O. Ezugwu), alissonm@mecanica.ufu.br (Á.R. Machado). 1 Tel.: +55 73 36805365. http://dx.doi.org/10.1016/j.ijrmhm.2014.06.019 0263-4368/© 2014 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Int. Journal of Refractory Metals and Hard Materials journal homepage: www.elsevier.com/locate/IJRMHM