抄録
Cutting tools of Ti(C, N)-Cr3C2 ceramics have better wear resistance than those of TiC-TiN cermet and WC-Co alloy tools for carbon steel. Ceramics of this system have the fracture toughness K1c of 2.5 MPa⋅ m1/2. Higher fracture toughness is necessary for wider application. Therefore, addition of metal and B4C to Ti(C, N)-Cr3C2 system was examined. The main results obtained are as follows:
(1) Adding each small amount of Ni and Co powder can improve not only density but also K1c of Ti(C, N)-20 wt%Cr3C2 ceramics.
(2) Adding over 10 wt%Cr3C2 to Ti(C, N)-Cr3C2-(2-4) wt%Ni system makes big chromium carbide lamps or slender pools in the structure. Adding 5 wt%Cr3C2 to system, however, makes homogeneous materials.
(3) These HIPed homogeneous materials have the transverse rupture strength of 900-1100 MPa and K1c of 3.5-4 MPa⋅m1/2. It is considered that the improvement of K1c was caused by Ni rich phase and the partial dissolution of Ni in the (Ti, Cr) (C, N) and chromium carbide phases.
(4) Ti(C, N)-Cr3C2-B4C bodies containing over 10 wt%Cr3C2 and 1-2 wt%B4C consist of (Ti, Cr) (C, N), CrB2 and a small quantity of chromium carbide.
(5) The sintered bodies of Ti(C, N)-20 wt%Cr3C2-2 wt%B4C-0.5 wt%Ni have the porosity of 0.1 vol%, the transverse rupture strength of 650 MPa and K1c of 3.8 MPa⋅m1/2. It is thought that the improvement of K1c is caused by the (Ti, Cr, Ni) (C, N) which is round grains, and a little chromium carbide and CrB2 which penetrate among the (Ti, Cr, Ni) (C, N) grains.
