Abstract—Alumina matrix composites with addition of hexagonal boron nitride (hBN), acting as solid lubricant, were produced. Main purpose of solid lubricants is to dispose the necessity of using cooling lubricants in machining process. Hot pressing was used as a consolidating process for Al 2 O 3 -x%wt.hBN (x=1/ 2,5/ 5 /7,5 /10) composites. Properties of sinters such as relative density, hardness, Young’s modulus and fracture toughness were examined. Obtained samples characterize by high relative density. Hardness and fracture toughness values allow the use of alumina – hBN composites for machining steels even in hardened condition. However it was observed that high weight content of hBN can negatively influence the mechanical properties of composites. Keywords—Alumina. Composites, Hexagonal boron nitride. Machining I. INTRODUCTION ONSTANTLY developing industry requires introduction of new technologies. Machining is one of the most important industry branch that needs to response to constant changes in automotive, aerospace and many other industries. Creating new materials, that characterize e.g. with improved hardness, reduced weight, higher fracture toughness, requires a way to machine them to desired shape. Cutting tools edges must have a specific properties in order to machine a chosen material. The main parameter is difference in hardness between cutting tool edge and machined material. Higher difference in favor of cutting tool edge can decrease wear of such tool in the machining process. In addition to hardness a cutting tool can’t crack or chip in the process [1]-[3]. Machining process performed using that cutting tool edge must also be environmentally safe. The vast majority of machining processes involves the use of cooling lubricants which are additional costs to the process. They are not friendly to environment and can even be hazardous for operating personnel. New concept that excludes the use of cooling lubricants involves a group of materials K. Broniszewski is with the Faculty of Materials Science and Engineering of Warsaw University of Technology, Woloska Str 141, 02-507 Poland, (phone/ fax:+48 22-234-57-19; e-mail k.broniszewski@inmat.pw.edu.pl) J. Woźniak is with the Faculty of Materials Science and Engineering of Warsaw University of Technology, Woloska Str 141, 02-507 Poland, (phone/ fax:+48 22-234-57-19) P. Orlowski is with the Faculty of Materials Science and Engineering of Warsaw University of Technology, Woloska Str 141, 02-507 Poland, (phone/ fax:+48 22-234-57-19) K. Czechowski is with the Institute of Advanced Manufacturing Technology, Wroclawska Str 37A, 30-011 Poland, (phone/ fax:+48 22-234- 57-19) A. Olszyna is with the Faculty of Materials Science and Engineering of Warsaw University of Technology, Woloska Str 141, 02-507 Poland, (phone/ fax: :+48 22-234-57-19) called solid lubricants. The solid lubricants are materials of structure very similar to graphite. Structure of used in this work hexagonal boron nitride is shown in Fig. 1. The atoms in planes are connected with strong chemical bonds and Fig. 1 Structure of hexagonal boron nitride (hBN) bonds. Such structure provides a possibility to slide successive planes with use of small strain even in room temperature [4]- Hexagonal boron nitride posses high melting point (~2800K) which is very important parameter for material used for cutting tool edge. Temperature at the contact area between tool and machined material can reach up to 1000ºC. It is very important that hBN stays in solid state in whole machining process. II. EXPERIMENT Powder substrates used in this work were: commercial one- phase α-Al 2 O 3 powder (chemical purity of 99,99%) and commercial one-phase hBN powder (chemical purity of 99,8%). Alumina powder characterize with mean particles size of 135±35nm and irregular shape Fig. 2. Hexagonal boron nitride powder characterize with mean particles size of 5,63±3,36μm an flake shape Fig. 3. Powders substrates were wet blended in isopropyl alcohol suspencion for 24h in attritor type mill. Powders mixtures were dried for 24h at 50ºC and then hot pressed at 1350ºC for 1h under pressure of 20MPa in argon atmosphere. Sinters production process scheme is presented in Fig. 4. As the result of sintering Al 2 O 3 -x%wt.hBN K. Broniszewski, J. Woźniak, K. Czechowski, P. Orlowski, A. Olszyna 2 3 C Properties of Al O – hBN Composites composites were created, where x = 1 /2,5 /5 /7,5 /10. [6]. successive planes are connected with weak Van der Walls World Academy of Science, Engineering and Technology International Journal of Materials and Metallurgical Engineering Vol:6, No:8, 2012 653 International Scholarly and Scientific Research & Innovation 6(8) 2012 scholar.waset.org/1307-6892/11427 International Science Index, Materials and Metallurgical Engineering Vol:6, No:8, 2012 waset.org/Publication/11427