Cermet insert and cutting tool

1. A titanium carbonitride-based cermet insert containing a titanium carbonitride-based cermet having a microstructure comprising 75 to 90 area % of a hard phase and the balance as a binding phase,

wherein the hard phase comprises:

(1) a first hard phase having a core-having structure in which a core portion includes a titanium carbonitride phase, and a peripheral portion includes a complex carbonitride phase having Ti, W, and one kind or two kinds of Ta and Nb (to be referred to as (Ti,W,Ta/Nb)CN);

(2) a second hard phase having a core-having structure in which both a core portion and a peripheral portion include (Ti,W,Ta/Nb)CN phases; and

(3) a third hard phase having a single phase structure including a titanium carbonitride phase, and

the binding phase contains a W—Co—Ni-based alloy having a composition comprising, as a ratio in the binding phase and by mass %, at least:

18 to 33 mass % of Co;

20 to 35 mass % of Ni;

5 mass % or less of Ti, and one kind or two kinds of Ta and Nb, the total amount thereof; and

40 to 60 mass % of W.

2. The titanium carbonitride-based cermet insert according to claim 1 , wherein the titanium carbonitride-based cermet is a sintered body of a compact having a blended composition comprising, by mass %, at least:

20 to 30% of tungsten carbide;

5 to 10% of one kind or two kinds of tantalum carbide and niobium carbide;

5 to 10% of Co;

5 to 10% of Ni; and

50 to 60% of titanium carbonitride.

3. A titanium carbonitride-based cermet insert containing a titanium carbonitride-based cermet having a microstructure comprising 75 to 93 area % of a hard phase and the balance as a binding phase,

wherein the hard phase comprises:

(1) a first hard phase having a core-having structure in which a core portion includes a titanium carbonitride phase, and a peripheral portion includes a complex carbonitride phase having Ti, W, one kind or two kinds of Ta and Nb, and one kind or two or more kinds of Zr, V and Mo (to be referred to as (Ti,W,Ta/Nb,Zr/V/Mo)CN);

(2) a second hard phase having a core-having structure in which both a core portion and a peripheral portion include (Ti,W,Ta/Nb,Zr/V/Mo)CN phases; and

(3) a third hard phase having a single phase structure including a titanium carbonitride phase, and

the binding phase contains a W—Co—Ni-based alloy having a composition comprising, as a ratio in the binding phase and by mass %, at least:

18 to 33 mass % of Co;

20 to 35 mass % of Ni;

Ti, one kind or two kinds of Ta and Nb, and one kind or two or more kinds of Zr, V and Mo, the total amount thereof is 5 mass % or less; and

40 to 60 mass % of W.

4. The titanium carbonitride-based cermet insert according to claim 3 , wherein the titanium carbonitride-based cermet is a sintered body of a compact having a blended composition comprising, by mass %, at least:

20 to 30% of tungsten carbide;

5 to 10% of one kind or two kinds of tantalum carbide and niobium carbide;

1 to 5% of one kind or two kinds of zirconium carbide, vanadium carbide and molybdenum carbide;

5 to 10% of Co;

5 to 10% of Ni; and

50 to 60% of titanium carbonitride.

5. A cermet insert containing a titanium carbonitride-based cermet comprising a sintered body containing Ti, one kind or two kinds of Ta and Nb, and W,

wherein a total of an amount of Ti converted as carbonitride, an amount of the one kind or two kinds of Ta and Nb converted as carbide, and an amount of W converted as carbide is 70 to 95 mass % as a ratio to the entire constitution that makes up the sintered body,

an amount of W converted as carbide is 20 to 35 mass % as a ratio to the entire constitution,

an amount of Co and Ni is 5 to 30 mass % as a ratio to the entire constitution,

the cermet insert has a microstructure comprising: a hard phase containing at least a complex carbonitride including Ti, W, and one kind or two kinds of Ta and Nb (to be referred to as (Ti,W,Ta/Nb)CN); and a binding phase including, as main components thereof, W and one kind or two kinds of Co and Ni, and

among the W contained in the entire constitution, 40 to 65 mass % is contained in the hard phase while the balance is contained in the binding phase.

6. The cermet insert according to claim 5 , wherein the hard phase further contains titanium carbonitride.

7. The cermet insert according to claim 5 , wherein an amount of Ti converted as carbonitride is 45 to 60 mass % as a ratio to the entire constitution, and an amount of one kind or two kinds of Ta and Nb converted as carbide is 5 to 10 mass % as a ratio to the entire constitution.

8. The cermet insert according to claim 5 , wherein the hard phase comprises one kind or two kinds of:

(1) a first hard phase having a core-having structure in which a core portion includes titanium carbonitride phase and a peripheral portion includes a (Ti,W,Ta/Nb)CN phase; and

(2) a second hard phase having a core-having structure in which both a core portion and a peripheral portion include (Ti,W,Ta/Nb)CN phases.

9. The cermet insert according to claim 6 , wherein the hard phase further comprises:

(3) a third hard phase having a single phase structure including a titanium carbonitride phase.

10. The cermet insert according to claim 5 , wherein Mo is further contained in one or both of the hard phase and the binding phase.

11. The cermet insert according to claim 5 , wherein the binding phase contains W at 40 to 60 mass % as a ratio in the binding phase.

12. A cutting tool comprising a holder and the cermet insert according to claim 5 held and fixed by the holder.