| 1. |
- Östberg, Gustaf, 1971, et al.
(författare)
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Effect of TaC on plastic deformation of WC-Co and Ti(C,N)-WC-Co
- 2006
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Ingår i: International Journal of Refractory Metals and Hard Materials. - : Elsevier BV. - 0263-4368. ; 24:1-2, s. 145-154
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Tidskriftsartikel (refereegranskat)abstract
- The plastic deformation resistance of metal cutting inserts made from a WC–Co cemented carbide, a Ti(C, N)–WC–Co cermet and corresponding materials with additions of TaC has been studied. The cermets were produced with both high and low carbon activity, resulting in a total of six materials. Ab initio calculations of some WC/WC grain boundary geometries suggest that both Co and Ta segregate substitutionally to the boundary and improve the grain boundary strength when substituting carbon. However, only Co segregation was found experimentally, probably due to (Ta, W)C formation. Plastic deformation tests were performed with a turning operation under controlled conditions. For the WC–Co, the addition of Ta had a positive effect for lower cutting speeds but at higher speeds the effect was negative. Three-point bending tests indicated a beneficial effect of Ta in WC–Co, which was also confirmed by internal friction (IF) measurements. However, after thermal cycling, the effect of Ta could be smaller, or even negative. The Ta cermet produced with low carbon activity exhibited a better plastic deformation resistance during cutting but no apparent effects of Ta could be seen either in IF measurements or in three-point bending tests of the cermets. However, a correlation was found between plastic deformation during turning and IF spectra. In the cermet materials, binder phase lamella formation promotes grain boundary sliding at high temperatures.
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| 2. |
- Östberg, Gustaf, 1971, et al.
(författare)
-
Mechanisms of plastic deformation of WC-Co and Ti(C,N)-WC-Co
- 2006
-
Ingår i: Int. J. Refract. Hard Mater.. - : Elsevier BV. - 0263-4368. ; 24:1-2, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- The deformation of the cutting edge of inserts made from WC–Co and Ti(C, N)–19%WC–Co upon radial turning was measured as a function of the cutting speed. Ab initio calculations of some grain boundary geometries in WC–Co indicated that Co segregates to WC/WC grain boundaries in submonolayer proportions and increases their strength and resistance to Co infiltration. This was also confirmed with TEM-EDX. SEM studies showed that during plastic deformation the hard phase skeletons in both materials were partly broken up and infiltrated by binder phase. TEM observations showed a considerable deformation of the WC grains and some infiltrated grain boundaries were facetted along low energy planes. In the cermet, no deformation of the hard phase grains could be seen. The plastic deformation at high temperatures observed by three-point bending corresponds to a number of relaxation processes, detected by internal friction, related to grain boundary sliding. Both materials deform by grain boundary sliding, accommodated in the cermet by Co diffusion and in the WC–Co by deformation of the hard phase and diffusion of Co.
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