Maciej Jan Kupczyk, 1 Andrzej Michalski, 2 Piotr Siwak, 1 and Marcin Rosinski 2 Evaluation of Cutting Edges Made of Nanocrystalline Cemented Carbides Sintered by the Pulse Plasma Method ABSTRACT: In our investigations, nanocrystalline WC-5 wt % Co was consolidated by the pulse plasma sintering method at various temperatures between 1320 and 1560 K under a pressure of 60 MPa for 300 s. The cemented carbides sintered at 1520 K have a relative density of 100 %, hardness of 2100 HV30, and tungsten carbides WC crystallite size of about 150–300 nm. An increase of the sintering temperature to 1560 K results in the increase of the WC crystallite size to about 300–500 nm and the hardness being decreased to 1980 HV30. The tool life of the cutting edges made of nanocrystalline cemented carbides sintered by the pulse plasma method is increased about two times in comparison with cutting edges made of standard and fine-grained cemented carbides during the turning of EN1.45.40 1H18N9T austenitic steel. KEYWORDS: nanomaterials, cutting edges, pulse plasma sintering method Introduction On the basis of the literature data 1–4 and our own investigations 5–8, a decrease reduction of the tungsten carbides WC grain size in WC-Co cemented carbides increases the fracture toughness, bending strength, and hardness. WC-Co cemented carbides are most often produced by sintering with the partici- pation of a liquid cobalt phase. The presence of a liquid cobalt phase during the WC-Co sintering causes the growth of the WC grains. The growth of the WC grains is due to the high rate of diffusion of WC through the liquid cobalt phase. In the newest sintering methods; for example, spark plasma sintering SPS, field assisted sintering FAST, and plasma assisted sintering PAS9–11, the sintering process is very short and carried out at a lower temperature than in the conventional methods. A characteristic feature of the SPS, FAST, and PAS methods is a current pulse for heating the powders during sintering. Spark discharges during a current pulse are ignited in the pores. The discharges formed in the pores remove absorbed gases and oxides from the surface of powder particles, thereby facilitating the formation of active contact between them. The present investigation was concerned with sintering nanocrystalline WC-5 wt % Co powders using a new pulse plasma sintering PPS method 12. As in the SPS, PAS, and FAST methods, in the PPS method the spark discharges during a current pulse are ignited in the pores. The phenomena occurring in the PPS process are shown in Fig. 1. In this article, the results of a comparative investigation of the durability of cutting edges made of nanocrystalline WC-5 wt % Co cemented carbides sintered by the pulse plasma method and cutting edges made of standard and fine-grained cemented carbides 1.5 m of the same chemical composition during the turning of EN1.45.40 1H18N9T austenitic steel are presented. Austenitic steel, widely applied in the food and chemical industry, belongs to hard machinable materials 13. The hard machinability of auste- nitic steel comes from a surface hardening phenomenon during machining. Therefore, the machining is carried out with very low cutting parameters. For this reason, the investigations of nanocrystalline ce- mented carbides were taken into consideration. The nanocrystalline cemented carbides are significantly harder and more wear resistant then the standard or fine-grained cemented carbides 4–6. Manuscript received July 15, 2010; accepted for publication January 3, 2011; published online January 2011. 1 Institute of Mechanical Technology, Poznan Univ. of Technology, Piotrowo 3 St., Poznan 60-965, Poland. 2 Faculty of Materials Science, Warsaw Univ. of Technology, Warsaw 02-507, Poland. Journal of ASTM International, Vol. 8, No. 2 Paper ID JAI103258 Available online at www.astm.org Copyright © 2011 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.