Ｔｉ（Ｃ，Ｎ）‐Ｃｒ３Ｃｒ２‐Ｍｅｔａｌ混合粉末の真空焼結

Abstract

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.