JPH0274572A - Bonding of sintered silicon carbide - Google Patents

Abstract

PURPOSE:To surely and stably produce a bonded SiC keeping high stability and strength at high temperature by contacting a plurality of sintered SiC materials interposing low-temperature-type SiC particles and high-temperature- type SiC particles between the materials and heating the assembly at a specific temperature to bond the materials. CONSTITUTION:Two or more sintered SiC materials are made to contact with each other in such a manner as to form a contact part at the contacting interface between low-temperature-type SiC particles composed of at least one kind of SiC selected from 3C and 2H polytypes and high-temperature-type SiC particles composed of at least one kind of SiC selected from 6H, 4H and 15R polytypes. The ratio of the contacting area of the low-temperature-type SiC particles and the high-temperature-type SiC particles is preferably >=50% of the total contacting interface. The obtained contacting product of sintered SiC is heated at 1700-2100 deg.C. The high-temperature-type SiC particle grows by taking the contacting low-temperature-type SiC particle to cause the substance transfer and the bonding of the sintered materials with the densified particles. A bonded SiC keeping high stability and strength at high temperature can be produced by this process without using high pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of bringing two sintered silicon carbide bodies into contact with each other and thermally joining them.

(Prior Art) Conventionally, as a method for joining two sintered bodies made of silicon carbide, (1) a method for joining silicon carbide using reaction sintering (
JP-A-61-132562, JP-A-62-197
(2) Diffusion bonding method of silicon carbide by pressure sintering (Japanese Unexamined Patent Publication No. 62-41777) is known.

Among these, the bonding method using reaction sintering enables the formation of complex shapes and large objects, and also allows high bonding strength to be obtained. Further, in a bonding method using pressure sintering, it is possible to achieve homogeneous bonding.

(Problem B to be solved by the invention) However, among the conventional joining methods mentioned above, in the joining method using reaction sintering, Si remains in the joint, resulting in poor high-temperature characteristics and, in some cases, the joining method using reaction sintering. Sometimes there were problems that required pressure.

Furthermore, the bonding method using pressure sintering requires high pressure and tends to leave pores, which makes bonding difficult.

The purpose of the present invention is to solve the above-mentioned problems, and to produce a silicon carbide bonded body that is stable and has high strength at high temperatures without requiring high pressure.
The present invention also aims to provide a method for joining silicon carbide sintered bodies that can be obtained reliably and stably.

(Means for Solving the Problems) The method for joining silicon carbide sintered bodies of the present invention is a method of heating and joining two silicon carbide sintered bodies by bringing them into contact with each other.
, S consisting of at least one type among 211 polytypes
The silicon carbide sintered body was brought into contact with the iC particles and the SiC particles consisting of at least one type of 61 (old 1.15R polytype) at the contact interface, at a temperature of 1700 to 2100°C. It is characterized by being heated with.

(Function) In the above-mentioned configuration, SiC particles (low-temperature type SiC particles) made of at least one type among 3C and 2H polytypes and SiC particles (high-temperature type SiC particles) made of at least one type among 6H, 4H, and 15R polytypes are used. SiC particles) and
After contacting to have a contact portion at the contact interface,
By heating at a predetermined temperature, a silicon carbide bonded body that is stable at high temperatures and has high strength can be obtained.

At the contact interface, the contact ratio at the contact portion between the high-temperature type SiC particles and the low-temperature type SiC particles is preferably 50% or more because more preferable high-temperature strength can be obtained.

To do this, the proportion of high-temperature type SiC particles and low-temperature type SiC particles in contact is calculated in advance stochastically from the proportion of each SiC particle in the sintered bodies to be joined, and the contact is made in a state where the contact rate is high. It is preferable.

A probabilistic calculation of the contact ratio between high-temperature SiC particles and low-temperature SiC particles is performed as follows. That is, (amount of high-temperature SiC crystals in the sintered body (volZ) x low-temperature SiC crystal fii (volZ) in the sintered body B) and (low-temperature SiC crystal M in the sintered body A (νO1χ)× It is expressed as the sum of high-temperature SiC crystal 1 (volZ)) in sintered body B.

When heated at a temperature of 1,700 to 2,100°C in contact with each other as described above, the high-temperature SiC particles take in the low-temperature SiC particles in contact and grow, resulting in mass transfer, densification, and bonding. do. That is, 1700
Since a bonded body with a good bonding limit cannot be obtained at a temperature other than ~2100°C, the heating temperature is set to 1700~2100°C.
It was limited to ℃.

(Example) An actual example will be explained below.

SiC powder (low temperature type SiC powder) consisting of at least one type among 3C, 2H polytypes and 6H, 4H, 15R
SiC powder (high-temperature type SiC powder) consisting of at least one type of polytype is prepared and fired, and then 111
Bonding was performed using a silicon carbide sintered body obtained by P treatment. The amounts of low-temperature type SiC crystals and high-temperature type SiC crystals in these silicon carbide sintered bodies are as shown in Table 1. In addition, at the contact interface, the contact area ratio of the high-temperature type SiC particles and the low-temperature type SiC particles at the contact area is
It was determined from the amount of iC crystals and the amount of low-temperature SiC crystals using the calculation method described above.

The joint surfaces of the silicon carbide sintered bodies to be joined were processed and smoothed using a surface grinder and a high-speed lapping machine. The surface roughness and flatness of the silicon carbide sintered bodies to be joined are as follows: surface roughness R = 0.1 μm or less, flatness 0.2
It is preferable that the thickness be less than μm.

To join the silicon carbide sintered bodies, they were heated at the temperatures shown in Table 1, and a jig was used to prevent the silicon carbide sintered bodies to be joined to be significantly misaligned. In addition, no pressure was applied during bonding, only the sample's own weight was used, and the heat treatment atmosphere was vacuum or inert.

Furthermore, the holding time depended on the size of the joint surfaces of the silicon carbide sintered bodies to be joined, the size of the silicon carbide sintered bodies themselves, and the heat treatment temperature, and was changed each time. Table 1 shows the results of Examples within the scope of the present invention and Comparative Examples outside the scope of the present invention.

In Table 1, the ultrasonic flaw detection test on the bonded surface was performed using a bonded body size of 38 x 36 x 6 mm and a probe frequency of 25 MH.
The presence or absence of defects was determined by performing the test on the joint surface under the following conditions: z, probe diameter 0.25'', and focal length 4''.

Further, the bonding strength was measured in accordance with JIS R1601 with the bonding surface located vertically at approximately the center between the inner spans. As shown in Table 1, the bonding strength of the bonded body at room temperature was comparable to the four-point bending strength of 650 to 750 MPa of the silicon carbide sintered body itself used for bonding. Also 1
The bonding strength at 400℃ is about 1 compared to the bonding strength at room temperature.
It had good high-temperature strength with only a decrease of about 0χ. Here, the items marked with a "-" in the table are those that have been separated during handling (including machining) after joining, and the joining strength is extremely low.Furthermore, Table 1 In Example 4, after bonding, at 1900°C in an argon atmosphere,
2000a tm conditions).

From the results in Table 1, it can be seen that the bonded bodies obtained by performing the bonding under the conditions within the scope of the present invention have a better bonded state and sufficient bonding strength compared to the bonded bodies of the comparative example. Was. However, at the heat treatment temperature of 1600°C in Comparative Example 3, the β phase changes to α phase.
There was insufficient phase transition, and the bonding state was poor.

Further, at the heat treatment temperature of 2200° C. in Comparative Example 4, abnormal grain growth occurred in the sintered bodies to be joined, so although the joining was good, the strength of the sintered bodies themselves to be joined was reduced.

Furthermore, from the results in Table 1, the larger the contact area ratio at the contact area between high-temperature SiC particles and low-temperature SiC particles at the contact interface, the better the bonding of the silicon carbide sintered bodies. From this, it is clear that bonding of silicon carbide sintered bodies consisting only of high-temperature type SiC particles on one side and low-temperature type SiC particles on the other side is the best. Furthermore, when joining silicon carbide sintered bodies having high-temperature type SiC particles as a main phase, a silicon carbide sintered body having low-temperature type SiC particles as a main phase is interposed between them.

Conversely, when joining silicon carbide sintered bodies containing low-temperature type SiC particles as the main phase, by interposing the silicon carbide sintered bodies containing high-temperature type SiC particles as the main phase, the high-temperature type Even when the contact area ratio at the contact portion between SiC particles and low-temperature SiC particles is as low as 50% or less, a bonded body having good bonding strength can be obtained.

(Effects of the Invention) From the above explanation, according to the method for joining silicon carbide sintered bodies of the present invention, SiC particles consisting of at least one type among 3C, 2+1 polytypes and at least one type among 6H, 41L 15R polytypes are combined. A silicon carbide bonded body that is stable at high temperatures and has high strength can be obtained by bringing SiC particles of different types into contact with each other so as to have a contact portion at the contact interface, and then heating at a predetermined temperature.

Claims (1)

[Claims] A method of heating and bonding one or more silicon carbide sintered bodies by bringing them into contact with each other, comprising SiC particles consisting of at least one type of 3C and 2H polytypes and of 6H, 4H and 15R polytypes. A silicon carbide sintered body is heated at a temperature of 1700 to 2100°C after the silicon carbide sintered body is brought into contact with SiC particles consisting of at least one type of the above so as to have a contact portion at the contact interface. Joining method. The ratio of the contact area between the SiC particles consisting of at least one type among 2, 3C, and 2H polytypes and the SiC particles consisting of at least one type among 6H, 4H, and 15R polytypes is 50% or more of the total contact interface. The method for joining silicon carbide sintered bodies according to claim 1.