JPH0535696B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ceramic tool material with excellent wear resistance, particularly to a tool material that can cut steel, cast iron, high nickel, aluminum, titanium, etc. at high speed. (Prior art) Silicon nitride ceramics, which are mainly composed of silicon nitride (Si ₃ N ₄ ), have excellent properties such as strength, oxidation resistance, abrasion resistance, thermal shock resistance, and corrosion resistance, so they are used as cutting tools. It is considered to be a desirable material and is attracting attention. However, Si ₃ N ₄ alone has poor quality stability and consistency compared to metals, and higher toughness is desired from the viewpoint of improved reliability and high properties. Therefore, JP-A-59-30770, JP-A-59-
There are attempts to use SiC whiskers as a reinforcing material to create composites, such as No. 54680 and JP-A No. 60-246268, but they are insufficient in both fracture resistance and wear resistance as cutting tool materials. The reality is that it has not been put to practical use as a tool material for high-speed cutting of heat-resistant steel and other materials. (Problems to be Solved by the Invention) In view of the above-mentioned circumstances, the present invention has been developed by modifying the surface layer of a β-sialon-based ceramic material having excellent high-temperature properties and toughness. The object is to create a cutting tool material that has both chipping resistance and wear resistance. (Means for Solving the Problems) The present invention has been made as a result of various studies to achieve the above object, and the outline thereof is as follows. A dense Al ₂ film with an average thickness of 0.1 to 5 μm is deposited on the surface of a composite sintered body mainly composed of 5 to 45% by weight of SiC whiskers, 3 to 20% by weight of Zr compound in terms of Zr, and the remainder β-sialon group ceramic. The first invention is a ceramic tool material provided with an O ₃ coating layer, and the Al ₂ O ₃
Before applying the coating layer, a ceramic tool material is coated with a dense Al ₂ O ₃ coating layer with an average thickness of 0.1 to 5 μm including the intermediate layer through an intermediate layer of AlN and/or AlON with a thickness of 3 μm or less. This is invention No. 2. First of all, if we talk about β-sialon group ceramic, the first invention and the second invention have the same compositional formula.
1 _to 25% by weight of Zr, Si _, Al,
It is desirable to have a glass phase containing O, N and unavoidable impurities, or one or more of Y, Mg, Ca, and rare earth elements. If this glass phase is less than 1% by weight, β-
The desired density cannot be obtained because Sialon cannot be sintered sufficiently, and if the amount is more than 25% by weight, the toughness and high-temperature strength will deteriorate, so the cutting tool will have a high temperature at the tip of the cutting edge during cutting. This is because it is not preferable as a material. Moreover, the addition of such a glass product is particularly effective when employing atmospheric pressure sintering or gas pressure sintering. The reason for specifying the z value here is that when z>1, the mechanical strength and toughness decrease, making it impossible to satisfy the mechanical properties required as a cutting tool material. Next, the reason why the amount of SiC whiskers is set to 5 to 45% by weight is that if it is less than 5% by weight, the toughness of the ceramic material will not improve, and if it exceeds 45% by weight, the sinterability will decrease. The above range is preferable since both of them are easily chipped during cutting and have poor chipping resistance. However, a more preferred range is 10 to 30% by weight, and the most preferred range is 15 to 25% by weight. The general definition of a whisker is that the cross-sectional area is 8×
10 ^-5 in ² or less and the length is 10 compared to the average diameter of the cross section
The whiskers used in the present invention have an average diameter of 0.2 to 1 μm and an average length of 5 μm.
~100μm, aspect ratio 5~500, Al,
The use of whisker-like crystals with a content of cationic impurities such as Ca, Mg, Ni, Fe, Mn, Co, Cr, etc. and SiO ₂ of 1.0% or less, with few constrictions, branches, and surface defects, is a highly tough dense material. It is preferable to obtain Also, the reason why the Zr compound is set at 3 to 20% by weight in terms of Zr is that if it is less than 3% by weight, the toughness improvement effect is insufficient, and if it exceeds 20% by weight, the hardness, thermal conductivity, and toughness of the sintered body will deteriorate. This is because the wear resistance and chipping resistance are unfavorable. Here, the Zr compound is not particularly limited, but for example, the X-ray diffraction results match fairly well with ZrO ₂ (monoclinic, tetragonal, cubic, or a coexistence thereof) and ZrO of ASTM Card No. 20-684. A compound like this. The effect of the Zr compound is that Zr, which is once dissolved in the glass phase during sintering, improves the wettability of the glass phase and SiC whiskers at the interface of the two, enabling a stronger bond between the two. The purpose is to improve toughness by acting so that the original characteristics of SiC whiskers can be fully demonstrated. In addition, although some of the Zr dissolved in the glass phase remains in the glass phase after sintering, most of it is reprecipitated from the glass phase in a crystalline phase that can be taken depending on the composition at that time and is present in the sintered body. . Therefore, for example, even when _ZrO2 exists in a sintered body, it can exist as monoclinic, tetragonal, cubic, or a coexistence of these depending on the composition, and there are differences in the crystal system. Even if there is, the effect of the Zr of the present application during sintering is the same, and therefore a sintered body with high strength and high toughness can be obtained. In addition, this β-sialon-based ceramic composite sintered body is sintered into a dense sintered body, which improves fracture toughness and
The bending strength can be set to a preferable value. The present invention relates to a cutting tool material in which an Al ₂ O ₃ coating layer is provided on the surface of such a β-sialon-based ceramic composite sintered body.
The Al ₂ O ₃ coating layer consists of the first invention in which it is provided directly on the surface of the sintered body, and the second invention in which it is provided through an intermediate layer made of AlN and/or AlON. However, in both cases Al ₂ O ₃ can be deposited by chemical vapor deposition (CVD). This CVD method heats a β-sialon ceramic composite sintered body to, for example, 1000°C to 1100°C, and then mixes AlCl ₃ , CO ₂ , H ₂ and optionally CO in a reaction vessel loaded with the β-sialon ceramic composite sintered body. This can be easily done by introducing gas. This processing temperature is 900℃ ~
The temperature is selected depending on the conditions within the range of 1300℃, but if the temperature is too high, the grain size of Al ₂ O ₃ tends to become coarse and the density tends to be lost, so it is preferable to process at a relatively low temperature for a long time. . In the first invention, when the thickness of the Al ₂ O ₃ coating layer is 0.1 to 5 μm, the wear resistance of Al ₂ O ₃ is exhibited, and an excessively rapid temperature gradient is generated in the surface layer during cutting. It is also preferable because it does not cause thermal cracks.
If the thickness of the Al ₂ O ₃ coating layer is thinner than 0.1 μm, the effect will be insufficient, and if it is thicker than 5 μm, it will easily peel off due to thermal shock, which is not preferable. Note that the thermal expansion coefficients of β-Sialon and Al ₂ O ₃ are significantly different, 3.0×10 ^-6 /℃ for the former and 7.8×10 ^-6 /℃ for the latter, so depending on the cutting conditions, peeling may occur in this coating layer. This may occur. In the second invention, in order to prevent this phenomenon, a thin layer of AlN or AlON is provided as an intermediate layer on a base material made of a β-sialon-based ceramic composite sintered body. It is possible to provide a stronger Al ₂ O ₃ coating layer by alleviating thermal stress due to the difference in thermal expansion coefficient between the Al 2 O 3 coating layer and the Al ₂ O ₃ coating layer. In this case, it is sufficient for the thickness of the intermediate layer to be 3 μm or less from the point of view of thermal stress relaxation, and the thickness of the Al ₂ O ₃ coating layer including the intermediate layer should be set to 0.1 to 5 μm to improve the durability during cutting. Preferable from the viewpoint of abrasion resistance and peeling resistance. If the thickness of the intermediate layer and the Al ₂ O ₃ layer including the intermediate layer is larger than these, cracks will easily form between the base material sintered body and the coating layer due to thermal shock, which may cause the cutting edge to break during cutting. Become. When the coating layer is constructed by CVD method,
It is provided by a precipitation reaction as described below. 1 2AlCl ₃ +3CO ₂ +3H ₂ →Al ₂ O ₃ +6HC1+3CO 2 2AlCl ₃ +N ₂ +3H ₂ →2AlN+6HCl 3 2AlCl ₃ +2CO ₂ +3H ₂ +N ₂ →2AlON+6HCl
The +2CO coating layer may be a single coating consisting only of Al ₂ O ₃ , but it is possible to provide one or more layers of AlN or AlON by the precipitation reaction shown in reaction formulas 2) and 3) above, and then apply a layer of AlN or AlON as shown in reaction formula 1). Multiple coating layers can be obtained by applying a layer of Al ₂ O ₃ by the precipitation reaction shown in FIG. In addition to the CVD method described above, the coating layer of the present invention can also be produced by a method such as a PVD method (physical vapor deposition method) or sputtering. (Example) Examples of the present invention will be described below. Example 1 Si ₃ N ₄ powder with an α rate of 90% and an average particle size of 0.6 μm, α-Al ₂ O ₃ powder with an average particle size of 1 μm, SiC whisker (SC-9 manufactured by ARCO Chemical Co., Ltd.) and an average particle size
Monoclinic ZrO ₂ with a diameter of 0.3 μm was blended in the proportions shown in Table 1, uniformly dispersed and mixed in ethanol for 4 hours, dried, and granulated to obtain a base material. This base material was hot pressed in a graphite mold at the firing temperature shown in the table for 60 minutes each at a pressure of 200 kg/ ^cm2 .
A densely sintered body was obtained. Next, this sintered body
After polishing into a SNGN432 chip shape, it is loaded into a stainless steel reaction vessel and heated to 1100℃ in a heating furnace.
After heating to _AlCl3 , supply _H2 and _CO2 gas
A mixed gas containing 12% by volume of AlCl ₃ , 23% by volume of CO ₂ and 65% by volume of H ₂ was flowed into the reaction vessel through the generator. In addition, the reaction vessel is heated to 20 to 30 Torr by a vacuum pump.
The thickness of the Al ₂ O ₃ coating layer was controlled by changing the reaction time. Cutting tests on high nickel alloy (Inconel 718), which is known as an extremely difficult-to-cut material, were conducted under the following conditions using the samples obtained in this way and the samples before coating. was measured. The cutting conditions are as follows. Cutting speed 200m/min Depth of cut 1.0mm Feed rate 0.2mm/rev Cutting time 10min The results are shown in Table 1. According to this, within the scope of the present invention (first invention), the surface of the β-sialon-based ceramic composite sintered body
Ceramic tool materials with an Al ₂ O ₃ coating layer of 0.1 μm to 5 μm have been found to have excellent wear resistance and do not cause defects even when cutting high-nickel alloys, which are difficult-to-cut materials. It has been proven that most of them either break or chip, or suffer a large amount of wear and cannot be put to practical use.

[Table] Example 2 Y ₂ O ₃ , MgO, CaO, with an average particle size of 2 μm or less,
A base powder obtained by mixing the proportions shown in Table 2 in the same manner as in Example 1 except that Dy ₂ O ₃ was added as a glass-forming compound other than Zr, Si, Al, O, and N was made into a graphite mold. Inside, hot pressing was carried out under conditions of temperature and pressure of 1750° C. x 200 Kg/cm ² for 60 minutes each to obtain a densely sintered body. Next, this sintered body was polished into a SNGN432 chip shape, then loaded into a stainless steel reaction vessel, heated to 1050℃, and then lowered to
A mixed gas of AlCl ₃ and H ₂ , N ₂ , and CO ₂ generated by passing HCl through an Al chip kept at 320°C was continuously changed and supplied into the reaction vessel. When forming a mixed interlayer of AlN−AlON
_AlCl3 gas 18% by volume, _N2 gas 12% by volume, _H2 gas
Initially flow 70% by volume, reduce _N2 gas by 2% by volume and increase _CO2 gas by 2% by volume every 30 minutes,
Finally, the _N2 gas was stopped and _Al2O3 was formed in _the outer layer. AlCl ₃ gas 18 to form AlN interlayer
A mixed gas of 12% by volume of _N2 gas and 70% by volume of _H2 gas was flowed. When forming the AlON intermediate layer, use _AlCl3 gas 12% by volume, _N2 gas 7% by volume, _CO2
A mixed gas of 16% by volume of gas and 65% by volume of _H2 gas was flowed. By varying the contact time of these mixed gases on the surface of the sintered body, chips with different thicknesses of the intermediate layer and the outer layer were obtained. Next, this chip was subjected to a milling test under the following cutting conditions. Cutting conditions Work material Chrome molybdenum steel SCM440 (HB280) Cutting speed 200m/min Depth of cut 1.5mm Feed rate 0.2mm/tooth The cutting test was performed until the cutting edge broke off, and the number of impacts until the cutting edge broke off was measured. The average values of the points are shown in Table 2 as the results. From these results, it was found that the second invention in which an intermediate layer of AlN or AlON was provided had an increased number of impacts and a longer cutting life compared to the one without this.

【table】

[Table] Example 3 The base powder was prepared in the same manner as in Example 2 except that ZrO ₂ and ZrN were used as the Zr compound in the proportions shown in Table 3, and the resulting sintered powder was sintered. The composition of the solid matrix was identified by X-ray diffraction. In addition, strength and toughness were measured as mechanical properties, and the results are shown in Table 3. From this result, it was found that regardless of the type of Zr compound added, after sintering, it existed in the sintered body as ZrO ₂ , ZrO, or a Zr compound thought to be an oxynitride of Zr, depending on the composition. In addition, even when it exists as Zro ₂ , it exists as monoclinic, tetragonal, cubic, or a coexistence of these depending on the composition, but it has been found that all of them result in sintered bodies that have the same high strength and high toughness. Ivy.

【table】

[Table] Example 4 In the same manner as in Example 2, except that β-sialon powder synthesized in advance at z = 0.3 was used in addition to Si ₃ N ₄ as the starting material, the ingredients were blended in the proportions shown in Table 4. The base powder obtained was molded to a size of 20□
After press-forming at 1.5 ton/cm ² , the material was sintered in a nitrogen gas atmosphere of 1 atm at 1750° C. for 2 hours to obtain a primary sintered body. Next, this sintered body was re-sintered at 1750° C. in a pressurized nitrogen gas atmosphere of 70 atmospheres for 2 hours to obtain a dense secondary sintered body. After processing the sintered body thus obtained in the same manner as in Example 2, an Al ₂ O ₃ coating layer was provided on the surface, and a cutting test was conducted under the following cutting conditions to determine the defects and damage after cutting. The amount of wear was measured. Cutting conditions Work material SCr420 Cutting speed 500m/min Depth of cut 1.0mm Feed rate 0.3mm/rev Cutting time 10 minutes Based on these results, within the scope of the present invention, an Al ₂ O ₃ coating layer was applied to the surface of the sintered body. It was demonstrated that the cutting material has excellent cutting performance with excellent fracture resistance and wear resistance.

[Table] (Effects of the invention) According to the first invention, an Al ₂ O _{3 coating film can be formed by utilizing the high toughness, which is an excellent characteristic of a β-sialon-based ceramic sintered body that is a composite of SiC whiskers and a Zr} compound. According to the second invention, a tool material with improved chipping resistance and wear resistance necessary for a cutting tool is provided by adding Al ₂ O ₃
When providing a coating film, by providing an AlN and/or AlON layer as an intermediate layer, it is possible to provide a cutting tool that has further improved thermal shock resistance than the one according to the first invention and has a significantly extended cutting life. can.

Claims (1)

[Claims] 1 5 to 45% by weight of SiC whiskers, Zr compound
3 to 20% by weight in terms of weight, the remainder being mainly composed of β-sialon ceramic, which has the composition formula Si _6-z AlzOzN _8-z (however, 0<z≦
1) and 1 to 25% by weight of β-sialon
An average film thickness of 0.1 to 5 μm is applied to the surface of a composite sintered body mainly composed of a glass phase containing Zr, Si, Al, O, N and unavoidable impurities or one or more of Y, Mg, Ca, and rare earth elements. High toughness characterized by a dense Al ₂ O ₃ coating layer.
Wear-resistant ceramic tool material 2 SiC whiskers 5-45% by weight, Zr compound
3 to 20% by weight in terms of weight, the remainder being mainly composed of β-sialon ceramic, which has the composition formula Si _6-z AlzOzN _8-z (however, 0<z≦
1) and 1 to 25% by weight of β-sialon
AlN with a thickness of 3 μm or less is applied to the surface of a composite sintered body mainly composed of a glass phase containing Zr, Si, Al, O, N and inevitable impurities or one or more of Y, Mg, Ca, and rare earth elements. High toughness and wear resistance characterized by a dense Al ₂ O ₃ coating layer with an average film thickness of 0.1 to 5 μm including the intermediate layer being provided through an intermediate layer consisting of one or more types of AlON. ceramic tool material.