JPS6411596B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is particularly suitable for use as wear-resistant tools such as rolls, guide rollers, seal rings, rocker arm tips, nozzles, dies, etc., and cutting tools where the work material is steel or cast iron. Suitable surface coating silicon nitride (hereinafter referred to as Si ₃ N ₄ )
The present invention relates to a base ceramic tool member. In general, Si ₃ N ₄ -based ceramics have excellent high-temperature strength and wear resistance, and are therefore used as wear-resistant tools and cutting tools used at high temperatures. The above-mentioned Si ₃ N _4- based ceramic contains oxides of Al, Mg, Zr, Y, and Si, as well as oxides of Al, Mg, Zr, Y, and Si, in weight% (hereinafter, % indicates weight%).
One or more of the following nitrides: 2 to 15%, with the remainder consisting of Si ₃ N ₄ and unavoidable impurities, and a porosity of 5% by volume or less is known. . Although tool parts manufactured with this Si ₃ N _4- based ceramic exhibit practical performance when cutting Ni-based heat-resistant alloys, Si ₃ N ₄ has a strong affinity with iron, and Because of this tendency, tool life is relatively short when cast iron or steel is used as the work material, or when this is used as the work material. In addition, the above-mentioned Si ₃ N _4- based ceramic is injected with elements from group 4a of the periodic table (i.e., Ti, Zr, and
A Si ₃ N _4- based ceramic containing one or more of Hf) carbides, nitrides, and carbonitrides in a proportion of 5 to 37% has been proposed. However, even with this Si ₃ N ₄ -based ceramic, the tool life is not fully satisfactory. Therefore, the present inventors developed the above-mentioned conventional Si ₃ N ₄ which is used in practical use as wear-resistant tools and cutting tools.
As a result of focusing on base ceramics and conducting research to extend tool life, we found that
Using sputtering method or ion beam method, at least the surface where wear occurs or the cutting surface of the Si ₃ N ₄ -based ceramic tool member is made of boron nitride (hereinafter referred to as BN) having a B/N atomic ratio of 1.0 to 1.2, When a coating layer having a structure in which cubic boron nitride (hereinafter referred to as CBN) is dispersed at a ratio of 2 to 30% by volume is formed on a substrate made of amorphous BN with an average layer thickness of 0.2 to 10 μm, the coating The layer has extremely low affinity with iron and has a high hardness of 3700 to 5000 Kg/ ^mm2 on the Vickers hardness, so it has improved wear resistance and is useful for forming a coating layer when cutting high-hardness steel, for example. 4~ compared to the case without
They obtained the knowledge that tool life could be extended by six times. This invention was made based on the above knowledge, and is based on carbides, nitrides, and carbonitrides of group 4a of the periodic table of elements (hereinafter collectively referred to as group 4a carbon/nitrides). One or more of: 5 to 37%, oxides of Al, Mg, Zr, Y, and Si, and Al
nitrides (hereinafter these are collectively referred to as oxides and
A Si ₃ N ₄ -based ceramic substrate containing 2 to 15% of at least one type of AlN (referred to as AlN), with the remainder consisting of Si ₃ N ₄ and unavoidable impurities, and having a porosity of 5% or less consisting of BN having a B/N atomic ratio of 1.0 to 1.2 at least on the surface that causes wear or on the cutting surface,
and a coating layer having a structure in which CBN is dispersed at a ratio of 2 to 30% by volume on a substrate made of amorphous BN,
Surface coating formed with an average layer thickness of 0.2 to 10 μm
This is a characteristic feature of Si ₃ N ₄ ceramic tool members. In the surface-coated Si ₃ N ₄ -based ceramic tool member of the present invention, the coating layer is formed by a sputtering method in which a high-purity hot-pressed hexagonal BN plate material is used as a target and high-frequency sputtering is performed in an N ₂ -containing Ar gas atmosphere; It is formed by an ion beam method in which B and N ion beams are simultaneously deposited, or by a method in which only B is deposited using a normal chemical vapor deposition method, and then a N ion beam is implanted into this B film. In this case, for example, in the case of a sputtering method, the B/N atomic ratio can be adjusted by controlling the substrate temperature, the N ₂ partial pressure in the N ₂ -containing Ar gas atmosphere, and the bias voltage. As a result of this you can
The CBN ratio will be adjusted,
Furthermore, the B/N atomic ratio in the coating layer can be identified by semi-quantitative analysis using Augier, and the CBN ratio can be identified by electron beam diffraction using an electron microscope. Next, in the surface-coated Si ₃ N ₄ ceramic tool member of the present invention, the component composition of the base, the B/N atomic ratio and CBN ratio of the coating layer, and the reason why the average layer thickness was limited as described above will be explained. do. A Component composition of the substrate (a) Group 4a carbon/nitride These components have the effect of suppressing the affinity with iron and improving wear resistance, but their content is less than 5%. However, the desired effect could not be obtained in the above action, and on the other hand, the content was 37%.
If the temperature exceeds 100%, the sinterability will decrease and the strength at room temperature will decrease, and the Si ₃ N ₄ content will be relatively too low, reducing the excellent high temperature strength and heat resistance provided by Si ₃ N ₄ . Since the impact resistance will decrease, the content should be increased from 5 to 5.
It was set at 37%. (b) Oxide/AlN These components act as sintering aids, but if their content is less than 2%, the desired sinterability cannot be secured;
If it exceeds 15%, the amount of liquid phase will be too large, grain growth will be significant, and strength and hardness will decrease, so the content was set at 2 to 15%. (c) Porosity If the porosity of the substrate exceeds 5%, the hardness decreases and it becomes difficult to ensure excellent wear resistance, so the porosity of the substrate was determined to be 5% or less. B Coating layer (a) B/N atomic ratio and CBN ratio The B/N atomic ratio affects the ratio of CBN dispersed and generated in the amorphous BN substrate, and therefore the B/N atomic ratio If is less than 1, the CBN ratio will be less than 2% by volume, and the hardness of the coating layer will decrease, making it impossible to secure a high hardness of 3700 Kg/mm ² or more in terms of Vickers hardness. On the other hand, the B/N atomic ratio
When it exceeds 1.2, the CBN ratio increases to more than 30% by volume, and the Bitkers hardness reaches 5000Kg/ ^mm2.
Although it has a high hardness exceeding Since it becomes easier, the B/N atomic ratio is
1.0 to 1.2, thereby increasing the CBN ratio to 2.
It was set at ~30% by volume. (b) Average layer thickness The BN coating layer according to the present invention has high hardness as described above and has extremely low affinity with iron, and exhibits excellent wear resistance in practical use. If the average layer thickness is less than 0.2 μm, the desired wear resistance cannot be achieved, while if the average layer thickness exceeds 10 μm,
Since chipping is likely to occur in the coating layer, the average layer thickness was set at 0.2 to 10 μm. Note that oxygen (O) is an inevitable impurity in the coating layer.
However, if the content is too large, it will adversely affect the properties of the coating layer, so it is desirable that the O/N atomic ratio is 0.15 or less. Next, the surface-coated Si ₃ N ₄ -base ceramic tool member of the present invention will be specifically explained with reference to Examples. As raw material powder, α-Si ₃ N ₄ powder and various 4a powders each have an average particle size within the range of 0.3 to 0.8 μm.
carbon and nitride powders, as well as various oxides and
Prepare AlN powder, blend these raw material powders into the composition shown in Table 1, wet mix in a ball mill for 50 hours, dry, and then press-form into a green compact at a pressure of 1 ton/cm ² . Next, this green compact is sintered in a nitrogen stream at a temperature of 1800°C for 30 minutes, and ground to the shape of ISO standard SNGN432, resulting in a component composition that is substantially the same as the blended composition. A Si ₃ N _4- based ceramic substrate having the porosity and hardness shown in Table 1 was then manufactured, and then a hexagonal plate was placed on one rake face of this substrate.

[Table] (*marked: outside the scope of the present invention)
Basic heating temperature: 200 to 500°C, atmosphere: N ₂ -containing Ar with a N ₂ /Ar ratio of 1/1 to 1/20, using a crystalline BN target and a high frequency sputtering method.
The present invention was carried out by forming the coating layer shown in Table 1 under the conditions of atmospheric pressure: 1 x 10 ^-4 to 5 x 10 ^-2 mmHg, bias voltage: 50 to 200 V, and reaction time: 0.5 to 20 hours. Surface-coated Si ₃ N ₄ -base ceramic cutting chip (hereinafter referred to as the coated chip of the present invention) 1
-8 and comparative surface-coated Si ₃ N ₄ -based ceramic cutting chips (hereinafter referred to as comparative coated chips) 1-4 were manufactured, respectively. It should be noted that the conditions of the coating layer (marked with * in Table 1) of Comparative Coated Chips 1 to 4 are outside the scope of the present invention. In addition, the B/N atomic ratio and CBN ratio of the coating layer are
It was measured by Auger analysis and transmission electron diffraction. Next, the various types of coated chips obtained as a result and four types of the Si ₃ N ₄ -based ceramic substrates (hereinafter referred to as conventional chips 1 to 4) before the formation of the coating layer were used.
Work material: FC30 round bar with H _B 230, cutting speed: 500 m/mm, feed: 0.3 mm, depth of cut: 2.5 mm, cutting oil: emulsion type, high-speed continuous cutting of cast iron under the following conditions. Tests were conducted and the wear depth of the rake face of the cutting edge, which is considered to be the end of the service life, was 200μm.
The cutting time was measured. The results of these measurements are shown in Table 1. From the results shown in Table 1, it can be seen that the coated chips 1 to 8 of the present invention are different from the conventional chips 1 to 4 without the formation of a coating layer.
It has a much longer service life compared to
As seen in Comparative Coated Chips 1 to 4, it is clear that if any of the conditions of the coating layer deviates from the scope of the present invention, satisfactory cutting performance will not be exhibited. As mentioned above, the surface-coated Si ₃ N _4- based ceramic tool member of the present invention has a coating layer that has high hardness and excellent adhesion to the Si ₃ N _4- based ceramic that makes up the base. Since it has a significantly low affinity for iron, it exhibits excellent wear resistance especially when the workpiece material is cast iron or steel, and is therefore suitable for use as wear-resistant tools or cutting tools. When maintained, it exhibits excellent performance over an extremely long period of time.

Claims (1)

[Scope of Claims] 1. One or more of carbides, nitrides, and carbonitrides of group 4a of the periodic table of elements: 5 to 37%, oxides of Al, Mg, Zr, Y, and Si, and Al
A silicon nitride group containing 2 to 15% of one or more of the following nitrides, with the remainder consisting of silicon nitride and unavoidable impurities (weight%), and having a porosity of 5% by volume or less At least on the surface where wear occurs or on the cutting surface of the ceramic substrate, a base material made of boron nitride having a B/N atomic ratio of 1.0 to 1.2 and amorphous boron nitride,
A surface-coated silicon nitride-based ceramic tool member formed by forming a coating layer having a structure in which cubic boron nitride is dispersed at a ratio of 30% by volume with an average layer thickness of 0.2 to 10 μm.