**5. Conclusions**

76 Tungsten Carbide – Processing and Applications

are exemplified in Figures 25 and 26.

The measurements of the wear resistance and friction coefficient permit classification of the as-infiltrated composites with respect to their tribological properties. Direct infiltration of green compacts with copper results in the highest wear resistance and almost the same friction coefficient of the as-infiltrated M3/2 and M3/2+30% WC composites. By comparing the wear resistance of composites received through direct infiltration of green compacts and infiltration of pre-sintered skeletons it is evident that the green compacts M3/2 and M3/2+30%WC compositions show 2÷3 times higher loss of mass than the tungsten carbide containing as-sintered materials infiltrated with copper. This can be explained by the diffusion of carbon and alloying of iron particles during sintering and chemical reaction between the tungsten monocarbide and HSS matrix. Friction coefficients are not highly influenced by the tungsten carbide additions, but the additions of 30% WC to high speed steel and infiltration with copper increase the wear resistance of these composites comparing to base material (M3/2 HSS infiltrated with copper). Wear tracks were analyzed by SEM to clarify wear mechanisms. Characteristic surface topographies after the wear test

**Figure 25.** The surface of the as-infiltrated M3/2 composites after examining the wear resistance

The surface topographies of M3/2 and M3/2+30%WC specimens indicate occurrence of different wear mechanisms (Figure 25 and 26). In Fig. 25, typical abrasion scratches are seen in the base material. As a result of abrasion, ferrous oxides are generated and then dispersed through the wear track. The carbides seen on the wear-surfaces are being crushed and pulled out of the matrix to act as abrasive particles which increase the coefficient of friction. Figure 25 provide evidence of ploughing and sideways displacement of material in M3/2. Figure 26 shows smearing of iron oxides over the surface of the as-infiltrated M3/2+30%WC

1. Infiltration of porous HSS skeleton with liquid copper has proved to be a suitable technique whereby fully dense HSS based materials are produced at low cost.

	- 2. Direct infiltration of green compacts with copper results in the higher hardness and higher resistance to wear of the M3/2 and M3/2+30 %WC composites, and allows to cut the production cost.

Tungsten Carbide as an Addition to High Speed Steel Based Composites 79

[8] L.A. Dobrzanski, [..]: Fabrication methods and heat treatment conditions effect on tribological properties of high speed steels, Journal of Metarials Processing Technology,

[9] E. Gordo, F. Velasco, N. Anto´n, J.M. Torralba: Wear mechanisms in high speed steel

[10] Farid Akhtar: Microstructure evolution and wear properties of in situ synthesized TiB2 and TiC reinforced steel matrix composites, Journal of Alloys and Compounds, 459

[12] Shizhong Wei, Jinhua Zhu, Liujie Xu: Effects of vanadium and carbon on microstructures and abrasive wear resistance of high speed steel, Tribology

[13] Z. Zalisz, A. Watts, S.C. Mitchell, A.S. Wronski: Friction and wear of lubricated M3 Class 2 sintered high speed steelwith and without TiC and MnS additives, Wear 258

[14] W. C. Zapata, C. E. Da Costa, J. M. Torralba: Wear and thermal behaviour of M2 highspeed steel reinforced with NbC composite, Journal of Materials science, 33 (1998) 3219

[15] G. A. Baglyuk and L. A. Poznyak: The sintering of powder metallurgy high-speed steel with activating additions, Powder Metallurgy and Metal Ceramics, Vol. 41, No 7-8,

[16] W. Khraisat, L. Nyborg and P. Sotkovszki: Effect of silicon, vanadium and nickel on microstructure of liquid phase sintered M3/2 grade high speed steel, Powder

[17] J. A. Jime´nez, M. Cars, G. Frommeyer and O. A. Ruano: Microstructural and mechanical characterisation of composite materials consisting of M3/2 high speed steel reinforced with niobium carbides, Powder Metallurgy 2005 Vol. 48 No. 4, s.

[18] J. D. Bolton and A. J. Gant: Phase reactions and chemical stability of ceramic carbide and solid lubricant particulate additions within sintered high speed steel matrix,

[19] J. D. Bolton and A. J. Gant: Heat treatment response of sintered M3/2 high speed steel composites containing additions of manganese sulphide, niobium carbide, and titanium

[20] M. Madej: Copper infiltrated high speed steel based composites with iron additions,

[21] M. Madej: The tribological properties of high speed steel based composites, Archives of

[22] H. G. Rutz and F. G. Hanejko: High density processing of high performance ferrous materials, international conference & Exhibition on powder Metallurgy & Particulate

reinforced with (NbC)p and (TaC)p MMCs, Wear 239 (2000), s. 251–259

[11] G. Hoyle: *High Speed Steels.* Butterworth & Co. Publishers. Cambridge 1998

157-158, (2004), s. 324-330.

International 39 (2006), s. 641–648

Metallurgy 2005 Vol. 48 No. 1 s. 33-38

Powder Metallurgy 1993 Vol. 36 No.4, s. 267-274.

carbide, Powder Metallurgy 1996 Vol. 39 No.1, s. 27-34.

Metallurgy and Materials, 2010 vol. 55 iss. 1 s. 61–68

Materials, May 8-11, 1994 - Toronto, Canada

Archives of Metallurgy and Materials, 2009 vol. 54 iss. 4 s. 1083–1091

(2008), s. 491–497

(2005), s. 701–711

2002, s. 366-368

– 3225

371-376

