Sintering + HIP of Ultrafine WC-Co Hardmetals

Abstract:

Article Preview

This work analyses the changes induced on the microstructure and mechanical properties of ultrafine (0.2 and 0.4 μm) hardmetal grade WC-7wt.% Co by HIP after vacuum sintering. A large HIP pressure (155 MPa) is applied to the ultrafine hardmetal system at different temperatures (1000, 1200 and 1400 °C). The well-known correlation between porosity reduction and fracture strength improvement is confirmed. Residual porosity left after liquid phase sintering is removed more effectively at HIP temperatures above the eutectic point of the alloy (1400 °C). In the absence of grain growth inhibitors, hardness decreases continuously, and WC-Co ultrafine microstructure coarsens as HIP temperature rises. However, for specimens containing VC and Cr3C2 additions, hardness increases as HIP temperature rises from 1200 to 1400 °C. It is proposed that this anomalous trend (confirmed by grain size observations) is related to the activation of coalescence mechanisms during solid state HIPing, which are inhibited by the presence of a liquid phase.

Info:

Periodical:

Edited by:

H. Balmori-Ramirez, J.G. Cabañas-Moreno, H.A. Calderon-Benavides, K. Ishizaki and A. Salinas-Rodriguez

Pages:

121-126

Citation:

A. Ordóñez et al., "Sintering + HIP of Ultrafine WC-Co Hardmetals", Materials Science Forum, Vol. 560, pp. 121-126, 2007

Online since:

November 2007

Export:

Price:

$38.00

[1] C. Chatfield: Powder Metall. Vol. 17 (1985), p.113.

[2] E. A. Almond and R. Roebuck: Int. J. Refract. Met. Hard Mater. Vol. 4 (1987), p.137.

[3] L. J. Prakash: Met. Powder Report Vol. 12 (1989), p.835.

[4] W. D. Schubert, A. Bock and B. Lux: Int. J. Refract. Hard Mater. Vol. 13 (1995), p.281.

[5] G. Gille, B. Szesny, K. Dreyer, H. Van Den Berg, J. Schmidt, T. Gestrich and G. Leitner: Proc. of the 15th Int. Plansee Seminar 2001, Vol. 2. P/M Hard Materials (Eds. G. Kneringer, P. Rödhammer and H. Wildner, Plansee Holding AG, Austria 2001).

[6] D. F. Carroll: Proc. of the 14th Int. Plansee Seminar 1997, Vol. 2 (Eds. G. Kneringer, P. Rödhammer and H. Wildner, Plansee Holding AG, Austria 1997).

[7] C. H. Allibert: Int. J. Refract. Hard Mater. Vol. 19 (2001), p.53.

[8] E. Lardner, and D. J. Bettle: Metals Mater. Vol. 7 (1973), p.540.

[9] O. Rüdiger and H. E. Exner: Powder Met. Int. Vol. 8 (1976), p.540.

[10] U. Engel and H. J. Hübner: J. Mat. Sci. Vol. 13 (1978), p. (2003).

[11] H. E. Exner: Int. Metals, Rev. Vol. 4 (1979), p.149.

[12] I. Gavish, R. Porat, A. Yairi and M. Leiderman: Proc. of 14th Int. Plansee Seminar 1997, Vol. 2, (Eds. G. Kneringer, P. Rödhammer and H. Wildner, Plansee Holding AG, Austria 1997).

[13] M. Liederman, O. Botstein and A. Rosen: Powder Metall. Vol. 40 (1997), p.219.

[14] I. Azcona, A. Ordóñez, J. M. Sánchez, F. Castro: J. Mater. Sci. Vol. 37 (2002), p.4189.

[15] C. Yang: Horizons in Powder Metallurgy, Part I (Schmid, Germany 1986).

[16] Cobalt Monograph (Centre d'Information du Cobalt, Belgium 1960).

[17] R. M. German: Sintering Theory and Practice (John Wiley & Sons, Inc., USA 1996).

[18] D. Kim, and A. Accary: Mater. Sci. Res., Vol 13 (1980), p.235.

[19] A. Bock, W. D. Schubert and B. Lux: Powder Metall. Int. Vol. 24 (1992), p.20.

[20] K. Choi, N. M. Hwang, D. Y. Kim: Powder Met. Vol. 43 (2000), p.168.

[21] S. Lay: Mat. Sci. Forum Vols. 426-432 (2003), p.4203.