JPH0513111B2 - - 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 a tool material capable of cutting copper, cast iron, high nickel, aluminum, titanium, etc. at high speed. <Conventional technology> Silicon nitride ceramics, whose main component is 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 attracting attention as a desirable material. However, Si ₃ N ₄ alone lacks quality stability and homogeneity 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-
No. 54680 and JP-A No. 60-246268, there are attempts to use SiC whiskers as a reinforcing material to create a composite material, but as a cutting tool material, although the chipping resistance can be improved, the wear resistance is poor. Because it is insufficient,
The reality is that it has not been put to practical use, especially as a tool material for high-speed cutting of heat-resistant steel and the like. <Problems to be Solved by the Invention> In view of the above-mentioned circumstances, the present invention aims to solve the problem by modifying the surface layer of a Si ₃ N ₄ -base ceramic material that has 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 was made as a result of various studies to achieve the above object, and an outline thereof is as follows. 5-40% by weight of SiC whiskers, 1% of sintering aid
The first ceramic tool material was prepared by providing a dense Al _{2 O 3 coating layer with an average thickness of 0.1 to 5 μm on the surface of a Si 3 N 4 - based} ceramic sintered body consisting of ~30% by weight and the balance being Si _{3 N} 4. According to the invention, before applying the Al ₂ O ₃ coating layer, an intermediate layer made of AlN or AlON with a thickness of 3 μm or less is provided, and the average film thickness including the intermediate layer is 0.1 to 5 μm.
The second invention provides a ceramic tool material provided with a dense Al ₂ O ₃ coating layer. First, let's talk about the Si ₃ N ₄ ceramic sintered body. Si ₃ N ₄ is a matrix material, and 1 to 30% by weight of a sintering aid is added, but this range is complex.
Although it varies depending on the amount of SiC whiskers, within the range necessary for sufficient densification, if it is less than 1% by weight, the desired density cannot be obtained.
Moreover, if the amount is more than 30% by weight, the high temperature properties deteriorate due to the glass phase, which is not preferable as a cutting tool material whose blade tip becomes hot during cutting. Moreover, the addition of such a sintering aid is particularly effective when employing the pressureless sintering method. Typical examples of sintering aids added here are Mg,
One or more metal oxides selected from the group of Al, Y, Zr and lanthanoids. Furthermore, SiC whiskers are added in an amount of 5 to 40% by weight, but if it is less than 5% by weight, no improvement in the toughness of the ceramic material is observed, while if it exceeds 40% by weight, the sinterability decreases and it is difficult to cut. The above range is preferable, more preferably 10 to 30% by weight, and most preferably 15 to 30% by weight, since it sometimes tends to chip and has poor chipping resistance.
It is in the range of 25% by weight. The general definition of a whisker is that the cross-sectional area is 8×
10 ^-5 in ² is a single crystal whose length is 10 times or more compared to the average diameter of the cross section, but the whiskers used in the present invention have an average diameter of 0.2 to 1 μm and an average length of 5 to 1 μm.
A thickness of 50 μm is preferable in order to obtain a dense body with high toughness. Further, by forming this ceramic material into a dense sintered body, it is possible to obtain preferable fracture toughness and bending strength. _The present invention relates to a cutting tool material in which a coating layer of _{Al 2 O 3 is} provided on the surface of such a _{Si 3 N 4} -based ceramic material. The first invention is provided directly on the surface of the material, and the second invention is provided via an intermediate layer made of AlN or AlON. However, in either case, Al ₂ O ₃ can be deposited by chemical vapor deposition (CVD). This CVD method involves heating a Si ₃ N _4- based ceramic material to, for example, 1000°C to 1100°C, and then flowing a mixed gas of AlCl ₃ , CO ₂ , H _{2 ,} and optionally CO into a reaction vessel loaded with the Si 3 N ceramic material. It can be easily done. The processing temperature is selected between 900℃ and 1300℃ depending on the conditions, but if the temperature is too high, the grain size of Al ₂ O ₃ tends to become coarse and the density is lost, so it is difficult to It is desirable to process for a long time. The thickness of _Al2O3 coating layer is 0.1 _~ 5μm
It is preferable because it exhibits the wear resistance of Al ₂ O ₃ and does not cause thermal cracks even if an excessively rapid temperature gradient occurs in the surface layer during cutting. If the thickness of the Al ₂ O ₃ coating layer is less than 0.1 μm, the effect is insufficient, and if it is thicker than 5 μm, it will easily peel off due to thermal shock. Next, the coefficient of thermal expansion of Si ₃ N ₄ and Al ₂ O ₃ is
Since the latter is significantly different from 3.2×10 ^-6 /°C and 7.8×10 ^-6 /°C, peeling may occur in this coating layer depending on the cutting conditions. In the second invention, in order to prevent this phenomenon, a base material made of Si ₃ N ₄ -based ceramic material is
By providing a thin layer of AlN or AlON as an intermediate layer, thermal stress due to the difference in thermal expansion coefficient between the base material and the Al ₂ O ₃ coating layer as described above can be alleviated, and a stronger Al ₂ O ₃ coating layer can be applied. be able to. In this case, the thickness of the intermediate layer described above is preferably 3 μm or less from the viewpoint of relaxing thermal stress, and the thickness of the Al ₂ O ₃ coating layer including the intermediate layer is 0.1 to 3 μm.
It is preferable to set the thickness to 5 μm from the viewpoint of wear resistance and peeling resistance during cutting. Including middle class and middle class
If the thickness of the Al ₂ O ₃ layer is larger than these, cracks are likely to occur between the sintered body as a base and the coating layer due to thermal shock, resulting in chipping of the cutting edge during cutting. 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 +6HCl+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 also possible to provide one or more layers of AlN or AlON by the precipitation reaction shown in reaction equations (2) and (3) above, and then react. By the precipitation reaction shown in equation (1)
Multiple coating layers can be obtained by providing a layer of Al ₂ O ₃ . The coating layer of the present invention is formed by the above-mentioned CVD method.
In addition, methods such as PVD (physical vapor deposition) and sputtering can also be used. <Example> Prototype test 1 SiC whiskers (Toka whiskers manufactured by Tokai Carbon Co., Ltd.) and sintering aids were uniformly dispersed and mixed into Si ₃ N ₄ powder with an average particle size of 0.6 μm at the ratio shown in the attached table (Table 1). After that, the temperature is 1700℃~1800℃ and the pressure is 200℃ in a graphite mold.
Pressure sintering was performed for 60 minutes each under Kg/cm ² conditions to obtain a dense sintered body. Next, this sintered body is SNGN433 with a chamfer of 0.05.
mm x 25℃, loaded into a stainless steel reaction vessel, heated to approximately 1100℃ in a heating furnace, and then heated with H ₂ and
Supply _CO2 gas and pass through _AlCl3 evaporator,
A mixed gas of 12% by volume AlCl ₃ , 23% by volume CO ₂ and 65% by volume H ₂ was flowed into the reaction vessel. In addition, the reaction vessel is heated by a vacuum pump for 20~
The temperature was maintained at 30 Torr, and the thickness of the Al ₂ O ₃ coating was varied by varying the reaction time. Using the samples obtained in this way and the samples before coating, cutting tests were conducted on a high nickel alloy (Inconel 718), which is known to be an extremely difficult-to-cut material, under the following conditions. was measured. The cutting conditions are as follows. Cutting speed 200m/min Depth of cut 1.5mm Feed rate 0.15mm/rev. Cutting time 10min The results are shown in Table 1. According to this, the surface of the Si ₃ N _4- based ceramic material having the composition according to the present invention (first invention) has a thickness of 0.1 to 5 μm.
Ceramic tool materials with an Al ₂ O ₃ coating layer do not cause defects when cutting high nickel alloys, which are difficult-to-cut materials, and have been found to have excellent wear resistance. It was proven that it could not be put to practical use because it caused breakage, chipping, or a large amount of wear.

【table】

[Table] Prototype Example 2 Add 20% by weight to Si ₃ N ₄ powder in the same manner as Prototype Example 1.
of SiC whiskers and 20 wt% Al ₂ O ₃ −ZrO ₂ (1:
4) The sintered body is sintered with the addition of the sintering aid.
Processed into SNGN432 and placed in CVD reaction vessel at 1050℃
After heating to , a mixed gas of AlCl ₃ , H ₂ , N ₂ , and CO ₂ was continuously changed and flowed into the reaction vessel. When forming a mixed interlayer of AlN−AlON
AlCl ₃ 18 vol%, N ₂ gas 12 vol%, H ₂ gas 70 vol% were initially flowed, and every 30 minutes N ₂ gas was decreased by 2 vol% and CO ₂ gas was increased by 2 vol%, and the final The _N2 gas was stopped to form _an outer layer of _Al2O3 . AlCl ₃ 18% by volume when forming the AlN intermediate layer;
A mixed gas of 12% by volume of N ₂ gas and 70% by volume of H ₂ gas was flowed. 12% by volume of AlCl ₃ to form the AlON interlayer;
_N2 gas 7% by volume, _CO2 gas 16% by volume, _H2 gas 65% by volume
A mixed gas of % by volume 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 FCD55 Cutting speed 200m/min Feed 0.3mm/tooth Depth of cut 1.5mm Number of impacts 5000 The results are shown in Table 2. According to this, AlN
It was found that the second invention in which an intermediate layer of AlON or AlON was provided had an increased impact resistance and a longer cutting life than those without this.

【table】

[Table] <Effects of the Invention> According to the first invention, an Al ₂ O ₃ coating film can be applied by utilizing the excellent toughness of the Si ₃ N _4- based ceramic sintered body composited with SiC whiskers. According to the second invention, when providing the Al ₂ O ₃ coating film, an AlN or AlON layer is provided. By providing it as an intermediate layer, it is possible to provide a cutting tool with improved impact resistance and significantly longer cutting life than the one according to the first invention.

Claims (1)

[Claims] 1. The surface of _a Si 3 N 4-based ceramic sintered body consisting of 5 to 40% by weight of SiC whiskers, 1 to 30% by weight of a sintering aid, and the remainder of Si _{3 N 4} . , the average film thickness
Wear _- resistant ceramic tool material provided with a dense _Al2O3 coating layer of 0.1-5μm. 2 SiC whiskers are 5 to 40% by weight of the whole, sintering aids are 1 to 30% by weight of the whole, and _the balance is Si _{3 N 4 .} A wear-resistant ceramic tool material provided with a dense Al ₂ O ₃ coating layer with an average thickness of 0.1 to 5 μm including the intermediate layer via an intermediate layer made of AlN or AlON.