JPS638262A - Sliding member made from silicon carbide sintered body and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention has excellent properties such as heat resistance, abrasion resistance, and corrosion resistance, and is used as a heat-resistant high-temperature material and a sliding material for sealing a shaft sealing part. The present invention relates to a sliding member made of an ultra-densified silicon carbide sintered body that is expected to be used as a material, and a method for manufacturing the same.

(Prior Art) Silicon carbide sintered bodies have excellent properties such as heat resistance, wear resistance, and corrosion resistance, and are therefore used in sliding components of gas turbines, for example, which require high temperature and high stress conditions. As,
It is also used as sliding members such as bearings and mechanical seals that require low wear and high thermal conductivity.

A sliding member made of a silicon carbide sintered body is produced by sintering a composition made of silicon carbide with boron and carbon added as sintering aids at a high temperature of 2000°C or higher and normal pressure in an inert atmosphere. Obtained by sintering method.

However, in the pressureless sintering method, pores and impurities (mainly sintering agent) segregate at grain boundaries, so the characteristics are that the bending strength is 40 to 80 kg/m rrI' and the density is 95% to 9.
8χ, thermal conductivity is limited to about 0.2 ca/cue ℃.

However, with this level of bending strength, at least 70 kg
It is unsatisfactory in terms of strength as a heat engine component such as a gas turbine sliding component that requires a bending strength of /m. In addition, silicon carbide single crystal has a high thermal conductivity of 1.2 cal/c, which is required for wear resistance and thermal conductivity in sliding parts such as mechanical seals and bearings.
However, the value decreases to the above value because pores, impurities, grain boundaries, etc. impede the propagation of lattice vibrations that control heat conduction. Furthermore, there is a risk that the wear resistance will deteriorate due to the growth of giant grains.

Therefore, in order to improve the strength, v, degree, thermal conductivity, wear resistance, etc. of silicon carbide sintered bodies, high-temperature pressure sintering methods are recommended, but this method is inferior in productivity and cannot be used in mass production. Moreover, since the shape of the sintered body is restricted, it is difficult to obtain a sintered body with a complicated shape having a blade portion, such as a gas turbine rotor, for example.

Therefore, a technique for obtaining a sintered body with high strength, high density, high thermal conductivity, and excellent wear resistance by HIP treatment (hot isostatic pressing method) was proposed in Japanese Patent Application Laid-open No. 80-255672. It was done.

(Problem to be solved by the invention) However, in the conventional old P treatment,
At a temperature of! Processing conditions of 0.000 atmospheres or higher are required.

In the IIP process which requires such high temperatures, a HIP processing furnace having extremely high high temperature strength is required, which increases the cost of the processing equipment.

In addition, expensive WRe thermocouples are used to measure temperatures at high temperatures around 2000°C, but they undergo severe thermal deterioration and become unusable after only a few cycles of use, resulting in trouble and maintenance problems. Inviting 1 original,
This is a factor that further increases the running cost of HIP processing, which is considered to be relatively high.

For this reason, it is required to perform the old P treatment of silicon carbide sintered bodies at the lowest possible temperature, but when boron or carbon-based materials are used as sintering aids, they are densified by diffusion creep. from.

It is necessary to process at a high temperature of 1850°C or higher, preferably 2000°C or higher.

As a result of intensive research in view of the background of the prior art, the present inventors have determined that a composition consisting of a mixture of silicon carbide and a sintering aid consisting of boron, aluminum or an aluminum compound, and non-bonded carbon is set within a certain composition range. At the same time, by pre-firing these at a certain temperature range, the density is 95.
% or more, the silicon carbide pre-fired body is heated to 100°C in a low temperature range of 1650 to less than 1850°C.
It has been found that by applying a pressure of 0 atmospheres or higher and performing HIP treatment, a sliding member made of an ultrafine, high-strength silicon carbide sintered body with a relative density close to 100% can be obtained.

(Means for Solving the Problems) In the sliding member made of a silicon carbide sintered body according to the present invention, silicon carbide is mixed with boron of 0.03 to 4 weight 2, O, OS~2
Heavy engineering aluminum or aluminum compounds and 0.
It is a sliding member made of a silicon carbide sintered body, which is obtained by sintering a molded body made of a mixture to which 5 to 15 weight 2 of non-bonded carbon is added, and further subjected to IIP treatment, and is made of aluminum or an aluminum compound. The addition of these compounds makes it possible to carry out low-temperature (11P) treatment, thereby producing an ultra-dense sliding member with a relative density close to toox.

Further, the method for producing a silicon carbide sintered body according to the present invention includes silicon carbide, boron in an amount of 0.03 to 4 tons by weight, aluminum or an aluminum compound in an amount of 0.05 to 2 tons by weight, and 0.5 tons by weight.
A molded body is formed from a mixture to which 15% by weight of non-bonded carbon is added, and this molded body is heated to 1750°C in an inert atmosphere.
Pre-fired at a temperature of 1850°C so that the density of the pre-fired body becomes 952 or higher, and then heated to 1650-185 in an inert atmosphere.
The HIP process is performed at a temperature of less than 0 degrees and a pressure of 1,000 atmospheres or more.

(Function) In the present invention, diffusion creep is promoted by solid solution diffusion of aluminum or an aluminum compound into silicon carbide grains and a high pressure of 1000 atmospheres or more, and the relative density is reduced to 1002 despite the low-temperature HIP treatment. A sliding member made of a high-strength silicon carbide sintered body with close to ultra-fine density can be obtained.

(Example) Using a fine powder of α-type or I-β type silicon carbide having an average particle size of IJL11 or less as a raw material, boron as a sintering aid is added to this raw material by 0.03 to 4 weight 2 (preferably <1 person 0
o05-0.15% by weight), aluminum or aluminum compound 0.05-2% by weight2 (preferably 0.1
~0.5 wt2) and 0.5-15 wt2 of non-bonded carbon
A raw material for molding is obtained by adding only an amount within the range of , and mixing thoroughly.

Thereafter, this raw material was press-molded, and the molded body was pre-fired at the pre-fire temperature shown in Table 1 below in an inert atmosphere (for example, argon atmosphere). Subsequently, the pre-fired body obtained by pre-fired was subjected to HIP treatment in an inert atmosphere (for example, argon atmosphere) under the +IP treatment conditions shown in Table 1. and No. 1
Sample No. 5 was obtained, and comparative samples without addition of Blend A as a sintering aid, that is, samples of the prior art, were obtained as No. 12 to No.
14.

(Left below) In Table 1 above, sample No. 2. No, 3. Na4
．． No.

10, No. 11 and No. 15 are within the scope of the present invention) IIP treatment at 1000 atmospheres or more and temperature 185
An ultrahigh-density sintered body with a relative density close to 10 oz was obtained even at a low temperature of less than 0° C., and the bending strength was also secured to be 70 Kg/mrn' or more.

In comparison, sample No. 1. No, 8. As for the comparative products indicated by No. +2, the HIP treatment temperature was set at 1850℃ or higher (
In particular, when the temperature was raised to a high temperature (1900° C. to 2000° C.), abnormal grain growth was observed, and furthermore, in Samples No. 12 to No. 14 of the prior art, in which A was not added as a sintering aid.

As for the HIP processing conditions, the density does not increase unless the temperature is 2000 atm and 1900°C or higher, and particle growth was observed in sample No. +2, and conversely, sample No. 14 and 18
At 50℃! & It was confirmed that there was a lack of density.

Furthermore, in the comparison products of samples N006 to N008, 1(I
As for the P treatment conditions, if the pressure is less than 1000 atm (300 atm), the relative density tends to decrease, which is undesirable.
A decrease in relative density was also observed when the temperature was lower than 1650°C as a treatment condition.

Figure 1 shows the relationship between the HIP return temperature and the density after IIP treatment for samples No. 001 to No. 5, No. 6 to No. 8.
and No. 12 to No. 14, respectively. In the figure, 1. Sample Nc+ within the range of the present invention, 2.
It can be seen that No. 3, No. 4, and No. 4 obtain values close to a relative density of 100 t in the low temperature region of 1700°C to 1850°C.

Furthermore, Table 2 shows the results of testing the sliding member made of the silicon carbide sintered body manufactured according to the present invention as a seal ring of a mechanical seal.

(The following is a blank space) In Table 2, it was revealed that the thermal conductivity was improved two to three times that of the conventional product, and the grain boundary strength was improved, resulting in excellent sliding properties.

Since silicon carbide sintered bodies are crystals with strong cleavability, when silicon carbide sintered bodies obtained by conventional pressureless sintering are used as sliding members of mechanical seals, mica often forms on the sliding surfaces. It is clear that the thermal shear stress caused by sliding causes cleavage wear of the silicon carbide sintered particles, and this is especially true for the abnormality of the silicon carbide sintered particles obtained by the pressureless sintering method. In the case of grain growth structures, this phenomenon is most remarkable.

However, when a sliding member made of a silicon carbide sintered body subjected to HIP treatment according to the present invention is used for a mechanical seal,
It exhibits excellent properties such as not causing any S wear on itself or the mating material, sintered carbon, and the sliding torque is lower than conventional ones, and it is very stable.

On the other hand, even in a sliding member made of HIP-treated silicon carbide sintered body, a decrease in strength of 1 level is observed when giant grains grow; however, when a sliding member made of this silicon carbide sintered body is used for a mechanical seal, There is no decrease in sliding properties as in the case of silicon carbide sintered bodies obtained by conventional pressureless sintering methods.

This fact is considered to be because the HIP treatment improves thermal conductivity and narrows grain boundary gaps, thereby improving grain boundary strength and suppressing cleavage wear of particles.

(Effects of the Invention) As explained above, according to the present invention, a molded body is formed in which aluminum or an aluminum compound is added and mixed in addition to a predetermined amount of boron and non-bonded carbon as a sintering aid, and this formed body is pre-calcined in an inert atmosphere at a temperature of 1750 to 1850 °C so that the density of the pre-calcined body is 95z or more, and then pre-fired in an inert atmosphere at a temperature of 1650 to less than 1850 °C and a pressure of 1000 atm or more)II' The sliding member manufactured by P treatment has solid solution diffusion of aluminum or an aluminum compound into silicon carbide grains, and 10
Diffusion creep is promoted by high pressures of over 1,000 atmospheres, so even though it is a low temperature process, it is super! lkS
It is possible to obtain a sliding member made of a silicon carbide sintered body having high strength characteristics, high thermal conductivity, and excellent sliding characteristics.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the old P treatment temperature and the density after the IIP treatment. Patent applicant Hiki Pillar Kogyo Co., Ltd. Agent Patent attorney Takashi Suzue Procedural amendment 1, Indication of case Patent application No. 150124/1982 2 Title of invention Sliding member made of silicon carbide sintered body and its Manufacturing method 3
, Relationship with the case of the person making the amendment Patent applicant Nippon Pillar Industries Co., Ltd. 4 Address of agent Tatsumi Umeda Building 8-1 Kamiyama-cho, Kita-ku, Osaka City Claims column and drawings (1) of the specification Replace the statement in the claims column of the document with another statement. Claims (1) 0.03 to 4% by weight of boron in silicon carbide. A silicon carbide sintered product characterized in that a molded body made of a mixture to which 0.05 to 2% by weight of aluminum or an aluminum compound and 0.5 to 15% by weight of non-bonded carbon is added is sintered and further subjected to IIP treatment. A sliding member made of a solid body. (2) 0.03-4 Mz boron in silicon carbide. A molded body is formed from a mixture of 0.05 to 2% by weight of aluminum or an aluminum compound and 0.5 to 15% by weight of unbonded carbon, and the molded body is heated in an inert atmosphere at a temperature of 1750 to 1950°C. A silicon carbide sintered body characterized by being pre-fired so that the density of the pre-fired body becomes 95X or more, and then subjected to HIP treatment in an inert atmosphere at a temperature of less than 1850-1850°C and a pressure of 1000 atm or more. A method for manufacturing a sliding member. 8 of

Claims (2)

[Claims] (1) 0.03-4% by weight of boron in silicon carbide, 0.0
From a silicon carbide sintered body characterized by sintering a molded body made of a mixture to which 5 to 2% by weight of aluminum or an aluminum compound and 0.5 to 15% by weight of non-bonded carbon are added, and further subjected to HIP treatment. A sliding member. (2) 0.03-4% by weight of boron in silicon carbide, 0.0
A molded body is formed from a mixture to which 5 to 2% by weight of aluminum or an aluminum compound and 0.5 to 15% by weight of unbonded carbon are added, and this molded body is heated for 1 hour in an inert atmosphere.
Pre-fired at a temperature of 750-950°C so that the density of the pre-fired body becomes 95% or more, and then heated at a temperature of 1650-950°C in an inert atmosphere.
HI at temperatures below 1850℃ and pressures above 1000 atm
A method for manufacturing a sliding member made of a silicon carbide sintered body, characterized by subjecting it to P treatment.