Cemented carbide with alternative binder

Abstract

The present disclosure relates to a cutting tool including a cemented carbide substrate having WC, gamma phase and a binder phase. The substrate is provided with a binder phase enriched surface zone, which is depleted of gamma phase, wherein no graphite and no ETA phase is present in the microstructure and wherein the binder phase is a high entropy alloy.

Claims

1. A cutting tool comprising a cemented carbide substrate, wherein said substrate comprises a microstructure of WC, a gamma phase comprising (W,M)C and/or (W,M)(C,N) wherein M is one or more of Ti, Ta, Nb, Hf, Zr and V, and a binder phase, said substrate including a binder phase enriched surface zone which is depleted of gamma phase, wherein no graphite and no eta phase is present in the microstructure of said substrate and wherein the binder phase is a high entropy alloy comprising 4 or more elements selected from Co, Cr, Cu, W, Fe, Ni, Mo and Mn wherein the amount of each element is between 5 to 35 at % of the total amount of the high entropy alloy.

2. The cutting tool according to claim 1, wherein at least one of the elements in the high entropy alloy is selected from Cr, Fe, Ni and Co.

3. The cutting tool according to claim 1, wherein at least two of the elements in the high entropy alloy are selected from Cr, Fe, Ni and Co.

4. The cutting tool according to claim 1, wherein the high entropy alloy includes Co, Cr, Fe and Ni.

5. The cutting tool according to claim 1, wherein the high entropy alloy includes Co, Cu, Cr, Fe and Ni.

6. The cutting tool according to claim 1, wherein a thickness of the surface zone is between 2 and 100 μm.

7. The cutting tool according to claim 1, wherein an amount of the gamma phase is between 3 to 25 vol %.

8. The cutting tool according to claim 1, wherein the substrate is provided with a coating.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a cross-section of a cutting tool according to the present disclosure.

DETAILED DESCRIPTION

(2) As shown in FIG. 1, cutting tool 10 includes a cemented carbide substrate 12, wherein the substrate comprises WC, gamma phase and a binder phase. The substrate 12 is provided with a binder phase enriched surface zone 14, which is depleted of gamma phase, wherein no graphite and no eta phase is present in the microstructure of the substrate and wherein the binder phase is a high entropy alloy. Substrate 12 is provided with a coating 16.

Example 1

(3) Cemented carbides were prepared from the raw material powders constituting raw materials forming the high entropy alloy, 0.76 wt % TiC, 0.50 wt % NbC, 2.9 wt % TaC, 1.52 wt % Ti(C,N), 0.02 wt % carbon black and balance WC with an average grain size (FSSS) of 4 μm. The elements forming the High entropy alloy i.e. Co, Cr, Fe and Ni, are added as 0.99 wt % Co, 2.02 wt % Cr.sub.3C.sub.2, 4.85 wt % Fe.sub.0.4Ni.sub.0.4Co.sub.0.2. The amount of each raw material is based in the total dry powder weight. The amount of each element to be part of the high entropy alloy is calculated to aim for a CoCrFeNi binder phase where the atomic ratio between the different elements is 1:1:1:1.

(4) The powders were milled together with a milling liquid (water/ethanol) and an organic binder (PEG) 2 wt % calculated from the total dry powder weight. The formed slurry was then pan dried and the dried powder was then subjected to a pressing operation to form a green body.

(5) The green body was then sintered at a temperature of 1470° C. for 1 h in vacuum. The sintered pieces were then subjected to a second sintering step gas pressure sintering at a temperature of 1520° C. and a pressure of 80 Bar for 1 h.

(6) In Table 1 it is shown different cemented carbides with the same composition as described above but with a variation in carbon content. All cemented carbides have been made according to the above, except for the carbon content which was adjusted with either carbon or metallic W to obtain the desired carbon content.

(7) The sintered body was studied in a light optical microscope (LOM) and the gradient zone (if present) was measured. The carbon content in Table 1 is the calculated value from the raw materials. The results are shown in Table 1.

(8) TABLE-US-00001 TABLE 1 Gradient zone Carbon content Eta phase/ Hardness (μm) (wt %) graphite Porosity (HV3) Sample 1 0 5.86 Eta phase A00B00C00E16 1954 Sample 2 0 5.94 Eta phase A02B00C00E16 1705 Sample 3 18 6.21 No A04B00C00 1798 Sample 5* 0 6.35 Graphite A08B06C06 n.a. *Only sintered in 1470° C., i.e. no GPS step

Example 2

(9) Cemented carbides were prepared in the same manner as described in Example 1 form raw materials forming the high entropy ally binder phase, 0.77 wt % TiC, 0.51 wt % NbC, 2.95 wt % TaC, 1.55 wt % Ti(C,N) and 0.08 wt % carbon black and the balance WC with an average grain size of 4 μm. The elements forming the High entropy alloy i.e. Co, Cr, Cu, Fe and Ni, are added as 0.77 wt % Co, 1.6 wt % Cr.sub.3C.sub.2, 3.85 wt % Fe.sub.0.4Ni.sub.0.4Co.sub.0.2, 1.68 wt % Cu. The amount of each element to be part of the high entropy alloy is calculated to aim for a CoCrCuFeNi binder phase where the atomic ratio between the different elements is 1:1:1:1:1.

(10) The samples were made in the same manner as in Example 1. In table 2, it is shown the results after the first sintering step, and in table 2, it is shown the results after the second sintering step, i.e. the gas pressure step.

(11) TABLE-US-00002 TABLE 2 Gradient zone Carbon content Eta phase/ Hardness (μm) (wt % in powder) graphite Porosity (HV3) Sample 1 0 5.95 Eta phase A08B00c00E16 1816 Sample 2 6 6.15 No A00B00C00 1631 Sample 3 10 6.25 No A00B02C00 1600 Sample 4 0 6.46 Graphite A08B00C06 n.a.

(12) As can be seen in the tables 1 and 2, a gradient is formed when the carbon balance is such that no eta phase and no graphite is present.

Example 3 PD Depression

(13) Inserts with the geometry CNMG 120408-PM geometry, made according to Example 1 (Sample 3), were tested in a turning operation under dry conditions. As a reference, the commercial grade GC4325 with the same geometry as Invention 1 was used, herein called Comparative 1. Both inserts were coated with the same coating.

(14) The work piece material was SS2541-03 (Al-oxidized), hardness 275-335 HB, with the following conditions:

(15) TABLE-US-00003 Vc 98-150 m/min f 0.7 mm/rev a.sub.p 2 mm
Measured quantity: Edge depression (μm).
The results are shown in Table 3.

(16) TABLE-US-00004 TABLE 3 Edge deformation (μm) Vc (m/min) 98 130 150 Invention 1 8 15 10 Comparative 1 20 46 60