Surface-coated cutting tool

Abstract

A surface-coated cutting tool comprises a hard coating layer that includes a TiAlN layer and is provided on a surface of a cutting tool body. In case the composition of the TiAlN layer is expressed by a formula: (Ti.sub.xAl.sub.1-x)N, 0.10≤x≤0.35 (here, x is in atomic ratio) is satisfied. In the TiAlN layer, a high Ti band-like region is present in a direction at 30 degrees or less with respect to a line normal to the surface of the cutting tool body. An average composition X of the Ti component in the high Ti band-like region satisfies (x+0.01)≤X≤(x+0.05), an average width W of the high Ti band-like region is 30 to 500 nm, and an average area ratio St of the high Ti band-like region is 3 to 50 area %.

Claims

1. A surface-coated cutting tool comprising: a cutting tool body; and a hard coating layer that is provided on a surface of the cutting tool body made of any of WC cemented carbide, TiCN cermet, or a cubic boron nitride sintered material, wherein the hard coating layer includes at least a complex nitride layer of Ti and Al with an average layer thickness of 0.5 to 10.0 μm, in a case where a composition of the complex nitride layer of Ti and Al is expressed by a composition formula: (Ti.sub.xAl.sub.1-x)N, the complex nitride layer of Ti and Al has an average composition satisfying 0.10≤x≤0.35 (here, x is in atomic ratio), in the complex nitride layer of Ti and Al, a band-like region, in which a composition of a Ti component is relatively high compared to an average composition x of the Ti component, is present at least in a direction at an angle of 30 degrees or less with respect to a line normal to the surface of the cutting tool body, an average width W of the band-like region, in which the composition of the Ti component is relatively high, is 30 to 500 nm, and an average area ratio of the band-like region, in which the composition of the Ti component is relatively high, to a longitudinal section of the complex nitride layer of Ti and Al is 3 to 50 area %.

2. The surface-coated cutting tool according to claim 1, wherein, in a case where the average composition of the Ti component in the band-like region in which the composition of the Ti component is relatively high is referred to as X, the average composition x of the Ti component in the complex nitride layer of Ti and Al and the X satisfy a relationship of (x+0.01)≤X≤(x+0.05).

3. The surface-coated cutting tool according to claim 1, wherein the complex nitride layer of Ti and Al has a mixed structure of crystal grains having a cubic structure and crystal grains having a hexagonal structure, and an average area ratio of the crystal grains having a cubic structure to a longitudinal section of the complex nitride layer of Ti and Al is 30 area % or more.

4. The surface-coated cutting tool according to claim 2, wherein the complex nitride layer of Ti and Al has a mixed structure of crystal grains having a cubic structure and crystal grains having a hexagonal structure, and an average area ratio of the crystal grains having a cubic structure to a longitudinal section of the complex nitride layer of Ti and Al is 30 area % or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawing(s), wherein like designations denote like elements in the various views, and wherein:

(2) FIG. 1 illustrates a schematic longitudinal sectional view of a TiAlN layer of a coated tool of the present invention.

(3) FIGS. 2A and 2B illustrate an arc ion plating (AIP) apparatus used for forming the TiAlN layer of the coated tool of the present invention, in which FIG. 2A is a schematic plan view, and FIG. 2B is a schematic front view.

DETAILED DESCRIPTION OF THE INVENTION

(4) Next, the coated tool of the invention will be described in detail with reference to examples.

(5) In a specific description, a coated tool using WC-based cemented carbide as a cutting tool body is described. However, the same applies to a coated tool using TiCN-based cermet or a cubic boron nitride-based sintered material as a cutting tool body.

EXAMPLES

(6) Production of Cutting Tool Body:

(7) As raw material powders, a Co powder, a TaC powder, a NbC powder, a TiC powder, a Cr.sub.3C.sub.2 powder, and a WC powder, all of which had an average particle size of 0.5 to 5 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 1. Wax was further added thereto, and the mixture was subjected to wet mixing by a ball mill for 72 hours and was dried under reduced pressure. Thereafter, the resultant was press-formed at a pressure of 100 MPa, and such compacts were sintered and processed into predetermined dimensions, whereby cutting tool bodies 1 and 2 made of WC-based cemented carbide with insert shapes according to ISO standard SEEN1203AFEN were produced.

(8) TABLE-US-00001 TABLE 1 Cutting tool Mixing composition (mass %) body type Co TiC TaC NbC Cr.sub.3C.sub.2 WC 1 8.0 1.5 — 2.6 0.3 Remainder 2 8.5 — 1.8 0.3 — Remainder

(9) The cutting tool bodies 1 and 2 were subjected to ultrasonic cleaning in acetone and were dried, and in this state, were mounted at positions distant from the center axis on the rotation table of the AIP apparatus illustrated in FIGS. 2A and 2B by predetermined distances in the radial direction along the outer circumferential portion, and Ti—Al alloy targets (cathode electrodes) having a predetermined composition were disposed in the AIP apparatus.

(10) First, while the inside of the apparatus was evacuated and held in a vacuum, the cutting tool bodies were heated to temperatures shown in Table 2 by a heater. Thereafter, a DC bias voltage shown in Table 2 was applied to the cutting tool bides that were rotated while revolving on the rotation table to cause an arc current shown in Table 2 to flow through the Ti—Al alloy targets (cathode electrodes) and generate an arc discharge such that the surfaces of the cutting tool bodies were subjected to bombardment cleaning.

(11) Next, nitrogen gas as a reaction gas was introduced into the apparatus to reach a nitrogen pressure shown in Table 2, the temperatures of the cutting tool bodies which were rotated while revolving on the rotation table were maintained in a temperature range shown in Table 2, an arc current shown in Table 2 was caused to flow through the Ti—Al alloy targets (cathode electrodes) to generate an arc discharge, a low DC bias voltage shown in Table 2 was applied to the cutting tool bodies for a predetermined time shown in Table 2, the bias voltage was then sequentially boosted linearly or stepwise in a graph in which the horizontal axis is time and the vertical axis is bias (−V) to follow an increase rate shown in Table 2, a high DC bias voltage shown in Table 2 was then applied, whereby a TiAlN layer was formed. Accordingly, each of present invention coated tools 1 to 9 (hereinafter, referred to as present invention cutting tools 1 to 9) having a target average layer thickness, the average composition x of the Ti component, the average area ratio S of the crystal grains having a cubic structure, a predetermined high Ti band-like region (the average composition X of the Ti component, the average width W, and the average area ratio St) shown in Table 4 was produced.

(12) For the purpose of comparison, a TiAlN layer was formed under bombardment conditions shown in Table 3 and film forming conditions also shown in Table 3 by using the AIP apparatus shown in FIGS. 2A and 2B, whereby each of comparative example coated tools 1 to 10 (hereinafter, comparative example cutting tools 1 to 10) shown in Table 5 was produced.

(13) The TiAlN layers of the present invention cutting tools 1 to 9 and the comparative example cutting tools 1 to 10 were measured in a cross-section using a scanning electron microscope, and the average layer thickness was calculated from the average value of measured values at five points.

(14) The composition of the Ti component in the TiAlN layer was measured by TEM-EDS in a visual field range of 0.4 μm or more in the film thickness direction and 1 μm or more in a direction parallel to the surface of the tool body at three points, and the average value of the measured values was obtained as the average composition x of the Ti component of the TiAlN layer.

(15) Table 4 and Table 5 show the values.

(16) Regarding the TiAlN layers of the present invention cutting tools 1 to 9 and the comparative example cutting tools 1 to 10, the presence or absence of the high Ti band-like region in the TiAlN layers was confirmed by TEM-EDS. In a case where the high Ti band-like region was present, the average composition X of the Ti component in the region, the average width W of the region, and the average area ratio St of the region to the longitudinal section of the TiAlN layer were obtained.

(17) Specifically, regarding the longitudinal section of the TiAlN layer as shown in FIG. 1, in a measurement image measured by TEM-EDS in a visual field in which a band-like width of at least about 500 nm is included, the composition of the Ti component at a plurality of measurement points on a straight line at an angle of 30 degrees of less with respect to a line normal to the surface of the body is measured, and by whether or not the measured value is in a range of (x+0.01) to (x+0.05), whether or not the straight line is a straight line that belongs to the high Ti band-like region is determined.

(18) Next, in a case where it is determined that the straight line is the straight line that belongs to the high Ti band-like region, the composition of the Ti component in a direction perpendicular to the straight line is measured, and a position where the measured composition of the Ti component deviates from the relationship of (x+0.01)≤X≤(x+0.05) is specified as the boundary of the high Ti band-like region.

(19) Next, the composition of the Ti component at a plurality of positions in the high Ti band-like region specified above is measured, and by averaging the compositions, the average composition X of the Ti component in the high Ti band-like region is obtained.

(20) Next, the contour of the high Ti band-like region specified above is determined, the width at a plurality of positions is measured, and by averaging the widths, the average width W of the high Ti band-like region is obtained.

(21) Furthermore, by obtaining the total area of the high Ti band-like region present in the area of the measured visual field from the obtained contour of the high Ti band-like region, the average area ratio St of the high Ti band-like region to the longitudinal section of the TiAlN layer is calculated.

(22) Table 4 and Table 5 show the values.

(23) In addition, regarding the TiAlN layers of the present invention cutting tools 1 to 9 and the comparative example cutting tools 1 to 10, the average area ratio S of the crystal grains having a cubic structure to the entire TiAlN layer was obtained by using the field emission scanning electron microscope and the electron backscatter diffraction apparatus.

(24) Specifically, in a state where the section of the TiAlN layer in the direction perpendicular to the surface of the cutting tool body was polished into a polished surface, the polished surface was set in the body tube of the field emission scanning electron microscope, and an electron beam was emitted toward each of the crystal grains present in a measurement range of the polished section, at an incident angle of 70 degrees with respect to the polished surface at an acceleration voltage of 15 kV and an emission current of 1 nA. Regarding a measurement range with a length of 100 μm in the direction parallel to the cutting tool body and a distance of equal to or less than the layer thickness along the section in the direction perpendicular to the surface of the cutting tool body, an electron backscatter diffraction image was measured at an interval of 0.01 μm/step. By analyzing the crystal structure of the individual crystal grains, the area ratio of the crystal grains having a cubic structure was measured.

(25) The above measurement was performed on five measurement ranges, and the average value thereof was calculated as the average area ratio S of the crystal grains having a cubic structure to the entire TiAlN layer.

(26) Table 4 and Table 5 show the values.

(27) TABLE-US-00002 TABLE 2 Bombardment condition TiAlN layer forming condition Cutting tool Al composition Cutting tool body DC bias of Target N.sub.2 gas body Cutting tool temperature voltage Arc current TiAl alloy pressure temperature Type body type (° C.) (−V) (A) (at %) (Pa) (° C.) Present 1 1 400 1000 100 80 4 400 invention 2 1 400 1000 100 70 4 400 cutting 3 1 400 1000 100 75 4 400 tool 4 1 400 1000 100 85 4 400 5 1 400 1000 100 73 4 400 6 2 400 1000 100 83 4 400 7 2 400 1000 100 75 4 400 8 2 400 1000 100 80 4 400 9 2 400 1000 100 73 4 400 TiAlN layer forming condition DC bias voltage Low bias voltage Bias High bias Voltage Application increasing voltage Arc current Type (−V) time (sec) rate (−V/sec) Voltage (−V) (A) Present 1 25 60.0 1.0 250 100 invention 2 15 60.0 1.0 300 100 cutting 3 30 60.0 1.0 300 100 tool 4 20 60.0 1.0 200 100 5 15 60.0 1.0 250 100 6 25 60.0 1.0 250 100 7 20 60.0 1.0 300 100 8 15 60.0 1.0 200 100 9 30 60.0 1.0 300 100

(28) TABLE-US-00003 TABLE 3 Bombardment condition TiAlN layer forming condition Cutting Cutting Al composition Cutting DC bias tool tool body DC bias Arc of Target N.sub.2 gas tool body voltage Arc body temperature voltage current TiAl alloy pressure temperature Voltage current Type type (° C.) (−V) (A) (at %) (Pa) (° C.) (−V) (A) Comparative 1 1 400 1000 100 80 4 400 50 100 example 2 1 400 1000 100 70 4 400 50 100 cutting 3 1 400 1000 100 75 4 400 50 100 tool 4 1 400 1000 100 85 4 400 50 100 5 1 400 1000 100 73 4 400 50 100 6 2 400 1000 100 83 4 400 50 100 7 2 400 1000 100 75 4 400 50 100 8 2 400 1000 100 80 4 400 50 100 9 2 400 1000 100 73 4 400 50 100 10 2 400 1000 100 70 4 400 50 100

(29) TABLE-US-00004 TABLE 4 TiAlN layer Confirmation of presence of high Ti band-like region High Ti band-like region Average Average area ratio Target Angle with re- Average Average Average area composition S of crystal average Presence spect to line composition X width W of ratio St of x of Ti grains having layer or absence normal to sur- of Ti of high Ti high Ti band- high Ti band- (atomic cubic structure thickness of band- face of cutting band-like region like region like region Type ratio) (area %) (μm) like region tool body (°) (atomic ratio) (nm) (area %) Present 1 0.2 35 5 Present 10 0.24 100 25.0 invention 2 0.32 95 4 Present 28 0.36 450 35.0 cutting 3 0.25 43 4.5 Present 15 0.28 35 15.0 tool 4 0.16 25 3 Present 5 0.2 150 40.0 5 0.28 65 6 Present 21 0.31 250 32.0 6 0.22 32 3.5 Present 8 0.24 65 22.0 7 0.26 39 5 Present 15 0.29 180 38.0 8 0.18 33 1 Present 18 0.21 300 4.0 9 0.29 55 9 Present 7 0.32 120 12.0

(30) TABLE-US-00005 TABLE 5 TiAlN layer Confirmation of presence of high Ti band-like region High Ti band-like region Average Average area ratio Target Angle with re- Average Average Average area composition S of crystal average Presence spect to line composition X width W of ratio St of x of Ti grains having layer or absence normal to sur- of Ti of high Ti high Ti band- high Ti band- (atomic cubic structure thickness of band-like face of cutting band-like region like region like region Type ratio) (area %) (μm) region tool body (°) (atomic ratio) (nm) (area %) Compar- 1 0.21 15 4 — — — — — ative 2 0.33 97 7 — — — — — example 3 0.27 18 5 — — — — — cutting 4 0.18 0 6 — — — — — tool 5 0.29 22 2 — — — — — 6 0.2 3 8 — — — — — 7 0.28 8 1 — — — — — 8 0.23 4 7 — — — — — 9 0.31 65 2 — — — — — 10 0.33 98 4 — — — — —

(31) Next, the present invention cutting tools 1 to 9 and the comparative example cutting tools 1 to 10 were subjected to dry high-speed face milling, which is a type of high-speed intermittent cutting, and a center-cut cutting test under the following conditions, and the flank wear width of a cutting edge was measured.

(32) Cutting test: dry high-speed face milling, center-cut cutting work

(33) Cutter diameter: 125 mm

(34) Work material: a JIS SCM445 block material with a width of 100 mm and a length of 365 mm

(35) Cutting speed: 360 m/min

(36) Depth of cut: 2.0 mm

(37) Feed per tooth: 0.2 mm/tooth

(38) Cutting time: 8 minutes.

(39) Table 6 shows the test results.

(40) TABLE-US-00006 TABLE 6 Wear width of flank face Cutting time Type (mm) Type (min) Present 1 0.22 Comparative 1 *4.5 invention 2 0.26 example 2 *2.8 cutting tool 3 0.18 cutting tool 3 *5.5 4 0.35 4 *1.8 5 0.27 5 *1.2 6 0.19 6 *2.3 7 0.23 7 *1.1 8 0.29 8 *3.6 9 0.26 9 *2.5 10 *4.3 (Note) *in comparative example cutting tools indicates a cutting time (min) until the end of a service life caused by the occurrence of chipping.

(41) From the results shown in Table 6, the coated tool of the present invention includes the TiAlN layer as the hard coating layer, and in the TiAlN layer, the high Ti band-like region is present in a direction at an angle of 30 degrees or less with respect to the line normal to the surface of the cutting tool body. Accordingly, the toughness is improved. In addition, since there is no anisotropy in the layer in the layer thickness direction, the coated tool of the present invention exhibits excellent chipping resistance and wear resistance during intermittent cutting work of alloy steel or the like during which high-temperature heat is generated and high impact and intermittent loads are exerted on a cutting edge.

(42) Contrary to this, it is obvious that the comparative example coated tools in which the high Ti band-like region is not formed in the TiAlN layer reaches the end of the service life within a relatively short period of time due to the occurrence of chipping.

INDUSTRIAL APPLICABILITY

(43) The coated tool of the invention exhibits excellent wear resistance for a long-term usage as well as excellent chipping resistance in a case of being provided for intermittent cutting work of alloy steel or the like. Therefore, the coated cutting tool of the present invention can satisfactorily cope with the factory automation (FA) of cutting apparatuses, power saving and energy saving during cutting work, and a further reduction in costs.