High strength sintered impact having excellent resistance to cratering

Powder of carbide, nitride and/or carbonitride of Ti shown in Table 1 was mixed with Al powder, and the mixture was placed in a vacuum furnace at 1,000° C. for 30 minutes. The mixture was milled by means of a ball mill to give a powdery binder.

The powdery binder was examined by XRD (X-ray diffraction), whereby carbide and nitride of Ti, Ti 2 AlN, TiAl 3 and TiAl were detected. The powdery binder had the same composition as that of the charged powdery raw materials.

This binder was mixed with cBN powder having an average particle size of 4.3 μm, W powder, WC powder, Co powder and/or Ni powder in various blending ratios, and the mixture was placed in the vacuum furnace at 1,000° C. for 20 minutes, followed by degassing. The resultant powder mixture was sintered under conditions having a pressure of 4.5 GPa and a temperature of 1,400° C. for 30 minutes.

The sintered material thus obtained was examined by XRD (X-ray diffraction). The detected compounds are shown in Table 1. Further, the results of wt % of the metal components Al, W, Co and Ni which are present as compounds in the sintered material, measured by an atomic emission spectroscopy and the % by volume, based on the sintered material, of cBN are shown in Table 1. The observation of texture of these sintered materials indicated that the binder phase is continuous. The wording “binder phase is continuous” in the context of the present Description means that cBN grains are maintained by the binder phase. In other words, said wording means that the original shape of the sintered body cannot be maintained when the binder phase is removed by means of fluoronitric acid in a tightly closed vessel having no evaporation of the acid.

Then, this sintered material was worked to give a tool (ISO number: SNGN 160408), and a tool life until failure in the high-speed interrupted cutting of hardened steel was examined under the following conditions. The results are shown in Table 1.

Matter to be cut

carburized steel SCM415, HRC61 120 mm (diameter)×280 mm (length), with six V-shaped grooves in the axial direction of the matter to be cut

Cutting conditions

cutting speed: cutting speed V=205 m/min, depth of cut: d=0.295 mm, feeding: f=0.115 mm/rev, DRY

As is apparent from Table 1, the sample No. 1 - 8 in which the content of the metal components Al, W. Co and Ni is less than 3%, and the sample No. 1 - 9 in which such a content exceeds 20% have a very short tool life until failure.

80% by weight of Ti nitride powder, 10% by weight of Al powder, 6% by weight of eutectic WC-Co powder, 2% by weight of Co powder and 2% by weight of Ni powder were mixed, and the mixture was placed in a vacuum furnace at 1,020° C. for 32 minutes. The mixture was milled by means of a ball mill to give a powdery binder. This binder was mixed with cBN powder having an average particle size of 3.9 μm in various blending ratios to give the cBN content of the vol % shown in Table 2. The mixture was placed in the vacuum furnace at 980° C. for 21 minutes, followed by degassing. The resultant powder mixture was sintered under conditions having a pressure of 4.8 GPa and a temperature of 1,380° C. for 15 minutes.

The amount of Al in these sintered materials was from 2% to 10% by weight, based on the sintered materials. The sum of W, Co and Ni in the sintered material was from 1% to 10% by weight, based on the sintered material. The weight ratio of W to W, Co and Ni: [W/(W+Co+Ni)] was from 0.2 to 0.6, and the weight ratio of Co to Co and Ni: [Co/(Co+Ni)] was from 0.6 to 0.95.

Then, this sintered material was worked to give a tool (ISO number: CNMA 160412), and the tool tool life until failure in the high-speed interrupted cutting of hardened steel was examined under the following conditions. The results are shown in Table 2.

Matter to be cut

carburized steel SCr420, HRC60 110 mm (diameter)×290 mm(length), with four U-shaped grooves in the axial direction of the matter to be cut

Cutting conditions

cutting speed: V=195 m/min,

depth of cut: d=0.198 mm, feeding: f=0.106 mm/rev, DRY

As is apparent from Table 2, both of the sample No. 2 - 1 having a smaller content of cBN and the sample No. 2 - 9 having a larger content of cBN have a very short failure tool life.

Ti nitride powder and Al powder shown in Table 3 were mixed in various blending ratios, and the mixture was placed in a vacuum furnace at 976° C. for 34 minutes. The mixture was milled by means of a ball mill to give a powdery binder. The powdery binder had the same composition as that of the charged powdery raw materials.

This binder was mixed with cBN powder having an average particle size of 2.8 μm, eutectic WC-Co powder, Co powder and Ni powder in various blending ratios so that the content of cBN was 60% by volume, based on the sintered material, and the mixture was placed in the vacuum furnace at 962° C. for 26 minutes, followed by degassing. The resultant powder mixture was sintered under conditions having a pressure of 4.7 GPa and a temperature of 1,420° C. for 10 minutes.

The results of measurement of wt % of the metal component of Al which is present as a compound in the sintered material by an atomic emission spectroscopy are shown in Table 3. The amount of the components Al, W, Co and Ni was from 3% to 20% by weight, based on the sintered material.

The wt % of the sum of W, Co and Ni in the sintered material was from 1% to 10%. The weight ratio of W to W, Co and Ni: [W/(W+Co+Ni)] was from 0.2 to 0.6, and the weight ratio of Co to Co and Ni: [Co/(Co+Ni)] was from 0.6 to 0.95.

Then, this sintered material was worked to give a tool (ISO number: TNMA 120408), and the tool life until failure in the high-speed interrupted cutting of hardened steel was examined under the following conditions. The results are shown in Table 3.

Matter to be cut

carburized steel SNCM420, HRC59 115 mm (diameter)×315 mm (length), with eight V-shaped grooves in the axial direction of the matter to be cut

Cutting conditions

cutting speed: V=212 m/min,

depth of cut: d=0.235 mm,

feeding: f=0.123 mm/rev, DRY

As is apparent from Table 3, tool life until failure is longer when the amount of Al is in the range of from 2% to 10% by weight.

80% by weight of Ti nitride powder and 20% by weight of Al powder were mixed, and the mixture was placed in a vacuum furnace at 1,012° C. for 30 minutes. The mixture was milled by means of a ball mill to give a powdery binder. The powdery binder was examined by XRD (X-ray diffraction), whereby carbide and nitride of Ti, Ti 2 AlN, TiAl 3 and TiAl were detected.

This binder was mixed with cBN powder having an average particle size of 4.6 μm, W powder, WC powder, Co powder and Ni powder in various blending ratios so that the content of cBN was 62% by volume based on the sintered material, and the mixture was placed in the vacuum furnace at 987° C. for 29 minutes, followed by degassing. The resultant powder mixture was sintered under conditions having a pressure of 4.6 GPa and a temperature of 1,390° C. for 30 minutes.

The results of measurement of wt %, based on the sintered material, of the metal components W, Co and Ni which are present as compounds (each element type and the amounts sum of elements) in the sintered material by means of an atomic emission spectroscopy, the weight ratio of W to W, Co and Ni, that is, [W/(W+Co+Ni)], and the weight ratio of Co to Co and Ni, that is, [Co/(Co+Ni)] are shown in Table 4.

The amount of the components Al was from 2% to 10% by weight, based on the sintered material. The amount of the components Al, W, Co and Ni was from 3% to 20% by weight, based on the sintered material.

Then, this sintered material was worked to give a tool (ISO number: SNGN 160408), and the tool life until failure in the high-speed interrupted cutting of hardened steel was examined under the following conditions. The results are shown in Table 4.

Matter to be cut p 1 carburized steel SCM415, HRC61 95 mm (diameter)×185 mm (length), with four V-shaped grooves in the axial direction of the matter to be cut

Cutting conditions

cutting speed: V=194 m/min, depth of cut: d=0.268 mm, feeding: f=0.097 mm/rev, DRY

As is shown in Table 4, when the content of sum of W+Co+Ni is from 1% to 10% by weight, when the weight ratio [W/(W+Co+Ni)] is from 0.2 to 0.6, and when the weight ratio [Co/(Co+Ni)] is from 0.6 to 0.95, the tool life until failure is longer.

75% by weight of Ti nitride, 15% by weight of Al powder, 3% by weight of WC powder, 5% by weight of Co powder and 2% by weight of Ni powder were mixed, and the mixture was placed in a vacuum furnace at 1,000° C. for 30 minutes. The mixture was milled by means of a ball mill to give a powdery binder.

This powdery binder was mixed with cBN powder having an average particle size of 4.3 μm and coated with nitride or boride of Ti, nitride or boride of Al, or a mutual solid solution thereof shown in Table 5 were mixed so that the cBN content was 63% by volume based on a sintered material, and the mixture was placed in the vacuum furnace at 1,000° C. for 20 minutes, followed by degassing. The coating was performed with the use of an RF sputtering PVD apparatus, and the film thickness of each coating layer was from 10 nm to 100 nm. The resultant powder mixture was sintered under conditions having a pressure of 4.5 GPa and a temperature of 1,400° C.

The resultant sintered materials were analyzed by AES (Auger Electron Spectroscopy) to measure a contact ratio among the cBN particles. The measurement was carried out by calculating the rate of the number of particles that are in contact with other CBN particles in an arbitrary region containing at least 100 cBN particles.

In these sintered materials, the amount of Al in the sintered material was from 2% to 10% by weight, based on the sintered material. The amount of the sum of W, Co and Ni in the sintered material was from 1% to 10% by weight, based on the sintered material. The weight ratio of W to W, Co and Ni, that is, [W/(W+Co+Ni)] was from 0.2 to 0.6, and the weight ratio of Co to Co and Ni, that is, [Co/(Co+Ni)] was from 0.6 to 0.95.

Then, the sintered material was worked to give a tool (ISO number: SNGN 160408), and the tool life until failure in the high-speed interrupted cutting of hardened steel was measured under the following conditions. The results are shown in Table 5.

Matter to be cut

carburized steel SCM440, HRC62 135 mm (diameter)×265 mm (length), with six U grooves in the axial direction of the matter to be cut

Cutting conditions

cutting speed: V=186 m/min,

depth of cut: d=0.195 mm,

feeding: f=0.105 mm/rev, DRY

The results of commercially available sintered materials manufactured without coating are also shown in Table 5 for comparisons.

As is shown in Table 5, it is understood that the commercially available sintered materials which do not have a coating and have more than 20% of the cBN particle contact rate have a short failure tool life.