Research of Structure and Properties of Hard Metals for Forming Rolls

In work the possibility of application of hard alloys for wares working under act of the variable thermal and mechanical loading was explored. Such materials must have the promoted maintenance of binder. Materials of the applied binders are expensive, and the search of the new compositions of binders is actual.

The Fe-WC (at 23% WC), Co-WC, Ni-WC, (Co+Ni)-WC, (Co+Ni+Cr_metallic)-WC, (Co+Ni+Cr₂C₃)-WC, (Ni+Cr_metallic)-WC (at 50% WC) systems were explored.

The following data are got:

1. The research of the experimental alloy Fe-WC (23% WC) got by the ESR method
   1. In the cast state a fine dendrite structure is got. It may be that after melting the powdery WC has represented itself as centers of crystallization.
   2. It is marked that in the structure there is a presence of the oriented needle-shaped excretions, probably having carbide nature. This phase did not succeed to be identified through the X-ray analysis, but the selection of the specified phase results in growth of microhardness, confirms supposition about its carbide nature.
   3. The structural heterogeneity appears after tempering from the temperature of 940-960^oC, that is related to partial dissolution of carbides in a binder. The structural heterogeneity is not observed almost after tempering from a temperature 1180-1200^oC.
   4. The X-ray analysis showed that at cooling from different temperatures, the quantity of remaining austenite and unidentified phase changes dependent.
2. The Research of alloys containing 50% WC with a different binder (the temperatures of baking 1300^oC and 1340^oC)
   1. The most homogeneous and a fine dispersive structure is got on the samples with the binder Co+Ni+Cr_metallic.
   2. The maximal hardness is got on an alloy with the Ni binder.
   3. The maximal porosity is at the alloy with the binder Ni+Cr_metallic, the minimal porosity is at the allow with the Ni binder.
   4. The Co binder possesses minimal microhardness, the Ni binder possesses maximal microhardness. Thus the Cr_metallic addition to Ni sharply lowered microhardness.
   5. There is no intensive oxidization of alloys up to the temperatures 1000-1050^oC.