JP2002361508A - Surface covered tungsten carbide base cemented carbide made drill with laminated covered layer displaying excellent chipping resistance under high speed drilling condition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface covered tungsten carbide base cemented carbide made drill a laminated covered layer of which displays excellent chipping resistance under a high speed drilling condition. SOLUTION: The surface covered tungsten carbide base cemented carbide made drill is constituted by physically evaporating the laminated covered layer to change in the thickness direction in overall average layer thickness of 0.5-5 μm on a CrN layer on the surface side through a mixed layer of a Cr2 N phase and a CrN phase from a metal Cr layer on the surface side of a base body on a surface of the tungsten carbide base cemented carbide base body, and respective average layer thickness of the metal Cr layer, the mixed layer and the CrN layer are made as the metal CrN layer: 0.05-0.3 μm, the mixed layer: 0.3-3 μm and the CrN layer: 0.1-2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for drilling high-hardness workpieces such as high-carbon steels and Ti alloys, particularly when high-speed drilling conditions, that is, high-speed rotation and high-feeding conditions are used. The present invention relates to a drill made of a surface-coated tungsten carbide-based cemented carbide in which a laminated coating layer exhibits excellent chipping resistance (hereinafter, referred to as a coated cemented carbide drill).

[0002]

2. Description of the Related Art Conventionally, coated carbide drills generally have a shape shown in, for example, a schematic front view in FIG. 1A and a schematic cross-sectional view of a groove forming portion in FIG. It is well known that it is used for drilling a work material such as steel or cast iron. Further, as the coated cemented carbide drill, for example, as described in Japanese Patent Application Laid-Open No. 3-197666, a hard substrate composed of a CrN layer is formed on the surface of a substrate made of a tungsten carbide-based cemented carbide (hereinafter, referred to as a cemented carbide substrate). Coated carbide drills formed by physical vapor deposition of a coating layer having an average layer thickness of 0.5 to 5 μm are known.

In general, the coated carbide drill uses an arc ion plating apparatus, which is a kind of physical vapor deposition apparatus schematically shown in FIG. In a state of heating at a temperature of 600 ° C. under a vacuum of 0.3 × 10 ⁻³ Pa, for example, a voltage of 35 V and a current of 130 A are applied between an anode electrode and a cathode electrode (evaporation source) on which metal Cr is set. An arc discharge is generated under the conditions, and at the same time, a nitrogen gas is introduced into the apparatus as a reaction gas, while, for example, -100 V
It is also well known that a coating layer made of a CrN layer is deposited on the surface of the cemented carbide substrate with an average layer thickness of 0.5 to 5 μm under the condition of applying a bias voltage of.

[0004]

In recent years, there has been a strong demand for labor saving, energy saving, and further cost reduction in cutting such as drilling, and in accordance with this, cutting has been accompanied by higher performance of cutting machines. However, in the above-mentioned conventional coated carbide drills, the high-carbon steel and Ti
There is no problem when used for drilling high-hardness work materials such as alloys under ordinary conditions, but these high-hardness work holes are particularly high-speed drilling with high mechanical and thermal shocks. Under the conditions, that is, under the high-feeding condition at a high rotation speed, chipping (micro chipping) is liable to occur particularly at the tip portion including the cutting surface (hereinafter, referred to as the tip cutting surface portion),
At present, the service life is reached in a relatively short time.

[0005]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, attention has been paid to the conventional coated carbide drills described above, and the coating layer has excellent chipping resistance even when applied to high-speed drilling conditions of high-hardness work materials such as high-carbon steel and Ti alloy. As a result of conducting research to develop a coated carbide drill that exhibits high durability, the coating layer on the substrate surface side is composed of a metal Cr layer with high toughness, while the coating layer on the surface side is a CrN layer with high hardness. A relatively soft Cr ₂ N phase and a hard C layer between the metallic Cr layer and the CrN layer.
A mixed layer in which the rN phase and the rN phase coexist at a predetermined mutual ratio, preferably, the ratio of the CrN phase to the Cr ₂ N phase is 10 to 90% by volume, more preferably 30 to 90%, as measured by an X-ray diffractometer.
A laminated coating layer having a mixed layer of 70% by volume is formed by physical vapor deposition on the surface of the superhard substrate. In this case, in particular, in this case, the average thickness of each of the metal Cr layer, the mixed layer, and the CrN layer is determined as follows. Metal Cr layer: 0.05 to 0.3 μm, Mixed layer: 0.3 to 3 μm, CrN layer: 0.1 to 2 μm, In the resulting coated carbide drill, The above-mentioned laminated coating layer is composed of metal C
The Cr layer has excellent toughness due to the r layer and excellent wear resistance due to the hard CrN layer, and the mixed layer is significantly harder than the above-mentioned soft metal Cr layer, especially during high-feed high-speed drilling. Has the effect of alleviating the stress generated in the laminated coating layer due to the coexistence of the lamination and suppressing the occurrence of chipping caused by the stress. Under the drilling condition, that is, even under the condition of high feed at high speed rotation, chipping caused by the laminated coating layer disappears, and the research result that excellent cutting performance can be exhibited for a long time has been obtained.

The present invention has been made on the basis of the above research results, and is provided on a surface of a cemented carbide substrate from a metal Cr layer on the substrate surface side through a mixed layer of a Cr ₂ N phase and a CrN phase. A laminated coating layer varying in the thickness direction is physically vapor-deposited on the CrN layer on the surface side with a total average layer thickness of 0.5 to 5 μm, and the average layer thickness of each of the above-described metal Cr layer, mixed layer, and CrN layer Metal Cr layer: 0.05 to 0.3 μm, Mixed layer: 0.3 to 3 μm, CrN layer: 0.1 to 2 μm. The laminated coating layer has excellent chipping resistance under high-speed drilling conditions. It is a feature of the coated carbide drill to be exhibited.

Next, in the coated carbide drill of the present invention, a metal Cr layer, a mixed layer,
The reason why the average thickness of the CrN layer is limited as described above will be described. (A) Metal Cr layer The metal Cr layer has an effect of imparting excellent toughness to the laminated coating layer by its own high toughness and preventing chipping from occurring at the tip cutting surface even in high-speed drilling. If the average layer thickness is less than 0.05 μm, the desired effect cannot be obtained in the above-described operation, while the average layer thickness is 0.3 μm
If the average thickness exceeds 0.05, the laminated coating layer undergoes thermoplastic deformation, which causes uneven wear and accelerates the progress of wear. Therefore, the average layer thickness is set to 0.05 to 0.3 μm.

(B) Mixed layer The mixed layer includes a relatively soft metallic Cr layer and a hard CrN
The layers coexist, and the occurrence of internal stress that cannot be avoided when high mechanical and thermal shocks are applied during high-speed drilling is suppressed between the metallic Cr layer and the CrN layer. Has the effect of preventing the occurrence of chipping due to the internal stress, but has an average layer thickness of 0.3 μm.
If the average layer thickness exceeds 3 μm, the metal C will not have the desired effect.
Since the effect of improving the toughness of the laminated coating layer by the r layer is impaired, and chipping is likely to occur, the average layer thickness is set to 0.
It was determined to be 3 to 3 μm. The ratio of the CrN phase to the Cr ₂ N phase in the mixed layer was measured with an X-ray diffractometer.
10 to 90% by volume, more preferably 30 to 70% by volume
If the hard CrN phase is less than 10% by volume, the relatively soft Cr ₂ N phase will exceed 90% by volume, and the hardness will decrease sharply. If the phase exceeds 90% by volume, the Cr ₂ N phase becomes less than 10% by volume. In this case, a sharp increase in hardness is unavoidable. This is because the hardness balance with the CrN layer is lost, and the desired effect of suppressing the generation of internal stress by the mixed layer cannot be obtained.

(C) CrN layer The CrN layer, which is located on the outermost surface of the laminated coating layer, has a function of remarkably improving its hardness and contributing to the improvement of wear resistance. If the thickness is less than 0.1 μm, the desired effect of improving wear resistance cannot be obtained. On the other hand, if the average thickness exceeds 2 μm, chipping is likely to occur under high-speed drilling conditions. 0.1 ~
It was determined to be 2 μm.

(D) Overall Average Layer Thickness The reason why the overall average layer thickness of the laminated coating layer is set to 0.5 to 5 μm is that if the layer thickness is less than 0.5 μm, the desired toughness that the laminated coating layer should have, The effect of suppressing internal stress generation and the hardness cannot be ensured in a well-balanced manner. As a result, excellent wear resistance cannot be ensured over a long period of time. On the other hand, when the average layer thickness exceeds 5 μm, metal This is because the above-described characteristic balance due to the Cr layer, the mixed layer, and the CrN layer is lost, and uneven wear and chipping are likely to occur.

[0011]

Next, the coated carbide drill of the present invention will be described in detail with reference to examples. As raw material powder,
WC powder, TaC powder, NbC powder, TiC powder, each having a predetermined average particle size in the range of 0.2 to 2 μm,
Prepare VC powder, Cr ₃ C ₂ powder and Co powder,
These raw material powders are blended in the blending composition shown in Table 1,
After wet mixing with a ball mill for 24 hours and drying, 100
It is press-molded into various compacts having a predetermined shape at a pressure of MPa, and these compacts are compacted in a vacuum atmosphere of 6 Pa at 7 ° C. /
The temperature was raised to a predetermined temperature in the range of 1370 to 1470 ° C. at a heating rate of 1 minute, kept at this temperature for 1 hour, and then sintered under the condition of furnace cooling to obtain a 3 mm diameter of 8 mm, 13 mm, and 26 mm. Kinds of round bar sintered bodies for forming a cemented carbide substrate were formed, and the above three kinds of round bar sintered bodies were subjected to grinding processing in a combination shown in Table 1 to obtain the diameter x length of the groove forming portion. Is 4mm ×
13mm, 8mm x 22mm, and 16mm x 45m
Carbide substrates A to L each having a size of m were manufactured.

Next, these super-hard substrates A to L are ultrasonically cleaned in acetone and dried, and each is charged into a usual arc ion plating apparatus illustrated in FIG. As a vapor source, a metal Cr target was mounted, and the inside of the apparatus was evacuated to 1.3 × 10 ⁻³ P
a. While maintaining the vacuum at a
After applying a bias voltage of -1000 V to the cemented carbide substrate, the surface of the cemented carbide substrate was washed by Cr ion bombardment with an arc current of 100 A for 5 minutes, and then the reaction atmosphere in the apparatus was set to 1.3 × 10 3. A vacuum atmosphere of ^-3 Pa, or a nitrogen atmosphere with a nitrogen partial pressure shown in Table 2, respectively, and an arc discharge current generated between the metal Cr target of the cathode electrode and the anode electrode and an applied voltage to the carbide substrate. By applying a bias voltage to the conditions shown in Table 2 and depositing a laminated coating layer having a target composition and a target layer thickness shown in Tables 3 and 4, the coated carbide drill 1 of the present invention was deposited.
-12 and comparative coated carbide drills 1-13, respectively. In addition, as shown in Table 4, the comparative coated carbide drills 1 to 13 had a configuration of the laminated coating layer, an average layer thickness of the constituent layers, and any one of the overall average layer thicknesses outside the scope of the present invention. The comparative coated carbide drill 1 among these comparative coated carbide drills 1 to 13 corresponds to the above-mentioned conventional coated carbide drill.

The center of the cross-section of the laminated coating layers of the coated carbide drills 1 to 12 of the present invention and the comparative coated carbide drills 1 to 13 obtained as described above was observed using an X-ray diffractometer. However, each of the target layers has substantially the same composition as the target composition shown in Table 2, and its thickness is measured in cross section using a scanning electron microscope. The average value was substantially the same as the thickness (average value measured at five points).

Next, the coated carbide drills 1 to 1 according to the present invention will be described.
2 and the comparative coated carbide drills 1 to 12, of the present invention coated carbide drills 1 to 4 and the comparative coated carbide drills 1 to 4, the work material: a plane size of 100 mm × 250 and a thickness of 50 mm Ti alloy sheet having a composition of Ti-6% Al-4% V, wet speed of Ti alloy under the following conditions: rotation speed: 2000 min ^-1 , hole depth: 5 mm, feed: 200 mm / min For the high-speed feed drilling test (using a water-soluble cutting oil), the coated carbide drills 5 to 8 of the present invention and the comparative coated carbide drills 5 to 8 are as follows: Work material: 100 mm × 250 plane dimension, 50 mm thickness Wet high-feed high-speed high-speed drilling test (using water-soluble cutting oil) of high carbon steel under the conditions of JIS S55C plate material, rotation speed: 7000 min ^-1 , hole depth: 15 mm, feed: 2100 mm / min. Invented Carbide drill 9-12
And the comparative coated carbide drills 9 to 12 are as follows: Work material: JIS S55C plate having a plane dimension of 100 mm × 250, thickness of 50 mm, rotation speed: 3000 min ⁻¹ , hole depth: 30 mm, feed: Wet high-speed high-speed drilling test (using water-soluble cutting oil) of high-carbon steel under the conditions of 800 mm / min., And the flank wear width of the cutting edge at the tip in any wet high-feed high-speed drilling test. The number of drilling operations was measured until 0.3 mm was reached, which is a measure of the service life. The measurement results are shown in Tables 2 and 3, respectively.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

According to the results shown in Tables 3 and 4, the coated carbide drills 1 to 12 according to the present invention, in each of which the laminated coating layer is composed of a metal Cr layer, a mixed layer, and a CrN layer, all have the CrN
In addition to the excellent wear resistance of the layer, the metal Cr layer and the mixed layer allow the laminated coating layer to have excellent chipping resistance, so that particularly high hardness coatings such as high carbon steel and Ti alloys can be obtained. Even in high-speed drilling of cutting materials, that is, high-speed drilling under high feed conditions at high speed rotation,
While excellent cutting performance is achieved without chipping on the tip cutting surface, the comparative coated carbide drills 1-1
As seen in FIG. 3, if any one of the constitution of the laminated coating layer, the average layer thickness of the constituent layers, and the overall average layer thickness is out of the range of the present invention, any of the abrasion resistance and the chipping resistance It is clear that the results are poor and do not show satisfactory cutting results. As described above, the coated carbide drill of the present invention can be used not only for drilling under ordinary conditions such as various kinds of steel and cast iron, but also for high carbon steel and T
Even in high-speed drilling of high-hardness workpieces such as i-alloys, chipping does not occur on the tip cutting surface, and excellent cutting performance is exhibited over a long period of time. Further, it is possible to satisfactorily cope with cost reduction.

[Brief description of the drawings]

FIG. 1A is a schematic front view of a coated carbide drill,
(B) is a schematic cross-sectional view of the same.

FIG. 2 is a schematic explanatory view of an arc ion plating apparatus.

Claims (1)

[Claims] 1. A lamination in which the thickness direction changes from a metal Cr layer on the surface side of a substrate to a CrN layer on the surface side via a mixed layer of a Cr ₂ N phase and a CrN phase on the surface of a tungsten carbide-based cemented carbide substrate. A coating layer is formed by physical vapor deposition with a total average layer thickness of 0.5 to 5 μm, and the above-described metal Cr layer, mixed layer, and CrN
High-speed drilling conditions characterized in that the average layer thickness of each layer is: metal Cr layer: 0.05 to 0.3 μm, mixed layer: 0.3 to 3 μm, CrN layer: 0.1 to 2 μm. Drill made of surface-coated tungsten carbide-based cemented carbide that exhibits excellent chipping resistance with a laminated coating layer.