In sintered WC-12%Fe-3%Ni alloy effects of carbon content on the mechanical properties have been investigated. Mixtures of WC, Fe, Ni powder and lamp black carbon have been ball milled and compacted. The compacts have been sintered at 1400℃ for 1 h in vacuum. Residual porosities in the sintered specimen could be eliminated completely by screening out the coarse agglomerates of Fe and Ni powers in the powder mixtures.
Carbon addition between 0 and 0.60% range showed a typical microstructural change. When 0.30% carbon was added, the two phase region consisting of WC grains and the matrix was observed. When the added carbon was less than 0.30%, complex carbides were formed. When the added carbon was more than 0.45%, free carbon was precipitated in the sintered specimen.
The hardness decreases with increasing carbon addition. With 0.30% carbon addition, TRS becomes maximum at about 2900 MPa. With decreasing carbon addition, TRS decreases markedly because of complex carbide formation. When the added carbon is large (0.60%), TRS also decreases markedly due to the formation of free carbon.
In the two phase region the mechanical properties of WC-12%Fe-3%Ni alloy are equal to those of WC-15% Co.
The hardness of the WC-12%Fe-3%Ni specimens increases by subzero treatment and this effect can be contributed to the formation of martensite.
