JPS6296372A - Method of joining silicon nitride base sintered body - 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 (Field of the Invention) The present invention relates to a method for firmly joining sintered bodies made of silicon nitride.

(Prior Art) In recent years, silicon nitride sintered bodies have been developed in a wide range of fields such as internal combustion engines and tool materials because of their excellent properties such as high strength, heat resistance, and corrosion resistance. However, parts of internal combustion engines and the like are designed based on advanced aerodynamics, material mechanics, and fracture mechanics, and are extremely complex and highly precise. In order to obtain such a complex shape, it is essential to divide each part into simple parts and join and integrate them at the same time as sintering or after sintering.

Conventionally, silicon nitride sintered bodies have been bonded by heat treatment with glass or activated metal such as Ti- or Zr interposed between them, by reaction sintering with metallic silicon interposed between them, or by reaction sintering with silicon nitride interposed between them. Methods such as hot pressing using a powder and a sintering aid have been considered.

(Problems to be Solved by the Invention) However, the bonding strength of glass bonding is low, and particularly when used at high temperatures, the strength tends to deteriorate extremely at temperatures above the glass transition temperature. In addition, when active metals are used, the wettability between the sintered body and the metal is incomplete, and peeling may occur due to thermal stress due to the difference in coefficient of thermal expansion. There were limits to sexuality. Furthermore, when reaction sintering is used, the sintered bodies become discontinuous, resulting in insufficient bonding strength, and when hot pressing is used, there are problems such as limitations in shape.

(Object of the Invention) The main purpose of the present invention is to solve the above-mentioned problems, and it is possible to join silicon nitride sintered bodies that can obtain excellent joint strength regardless of the shape of the sintered body. The present invention provides a method.

(Means for Solving the Problems) That is, according to the present invention, between the silicon nitride sintered bodies to be joined, one or more metals of group Ma of the periodic table are contained in an amount of 1 to 60% by weight. Provided is a method for joining silicon nitride sintered bodies, which is characterized by heating in a range of 1000 to 1800° C. in a nitrogen atmosphere with an aluminum alloy interposed therebetween.

The present invention will be explained in detail below.

According to the present invention, it is important to interpose an aluminum alloy containing a group MA metal of the periodic table (hereinafter simply referred to as a group MA metal) between the silicon nitride sintered bodies to be joined. It is difficult for the fine powder of the Ma group metal to exist stably in the atmosphere as a single substance, but it can be made to exist stably by alloying it. Moreover, since each component has high reactivity with nitrogen, it becomes possible to bond firmly to silicon nitride.

Note that when this alloy is interposed between the sintered bodies, it is interposed as a powder, a foil, or a film formed by sputtering or the like.

According to the present invention, the sintered body in which the above alloy is interposed has 1
000 to 1800℃, especially 1100 to 1700'C
(7) Heat treated in a nitrogen atmosphere.

This heat treatment causes the alloy to undergo the following nitriding reaction.

N.

RE-AI -” REN + AIN (RE
: MA group metals) The nitrides produced by this nitriding reaction increase their melting point and dissolve into the silicon nitride crystal phase or grain boundary phase in the silicon nitride sintered body, which reduces the strength of the joint, especially at high temperatures. It becomes possible to increase the strength of the time.

The Group IIIa metal used in the present invention is particularly Y.

Examples include Sc, La+Nd+Sm, Yb, Dy, etc., and one type or two or more types can be used, and among these, Y is particularly preferred.

The proportion of ma group metal in aluminum alloy is 1 to 60
It is set in a range of 10 to 50% by weight, preferably 10 to 50% by weight.

If the amount of the MA group metal is less than the above range, the reactivity with silicon nitride will decrease, making it impossible to form a homogeneous, high-strength bond; if it exceeds the above range, the proportion of the nitride of the MA group metal will increase, Becomes chemically unstable. Furthermore, the MA group metals are generally expensive and uneconomical.

At this time, if the temperature in the heat treatment is lower than 1000° C., the nitriding reaction and the reaction to silicon nitride will not proceed, making it impossible to obtain sufficient strength. On the other hand, when the temperature exceeds 1800°C, the decomposition becomes more intense due to the reaction between 5iJa and AIN.

Further, the nitrogen pressure during the heat treatment is preferably about 10 times the equilibrium nitrogen gas partial pressure of silicon nitride.

The alloy of the MA group metal and aluminum used in the present invention can be created by a normal method. For example, after mixing the respective metal powders,
It is obtained by melting at a temperature of 1500°C to 1500°C and then cooling.

According to the present invention, Si, A1.03,
It is also possible to add REz(h, etc.).

The silicon nitride sintered body used in the present invention includes:
There are no particular limitations, and any known sintered body may be used. For example, silicon nitride is the main component, and other components include oxides and nitrides of Group IIIa elements of the periodic table such as yttrium, or 5iOz, Al2O2, MgO% ZrO.
In addition to systems containing conventionally known sintering aids such as oxides such as oxides such as oxides such as oxides such as oxides such as oxides such as oxides such as

The invention is illustrated by the following example.

Example Alloy foil (0.1 mm) consisting of a Ma group metal-aluminum alloy having the composition shown in Table 1 was prepared by Si: +N492χ, Y2
It was inserted into a silicon nitride sintered body having a composition of 55% O and A1□033z, and heat-treated at the temperature shown in Table 1 for 1 hour in a nitrogen atmosphere of 1 atmosphere.

The obtained zygote was JISl? As is clear from Table 1, samples 1 to 5 of the present invention all had high bonding strengths at room temperature (RT), 1000°C, and 1200°C in four-point bending based on 1601. In particular, even at 1200°C, a bending strength of 10 Kg/mm2 or more was secured.

On the other hand, No. 6, which had a large amount of group I[[a metal, had the same strength at room temperature as the present invention, but was inferior in high temperature strength.

On the contrary, N11L7, which has a large amount of ^1, could not obtain sufficient strength at any temperature, and could hardly be measured at 1000°C and 1200°C.

(Effect of the invention) As described above, according to the present invention, periodic table IIIa
By interposing an alloy of a group metal and aluminum and heat-treating it in a nitrogen atmosphere, it is possible to improve the bonding strength, especially the bonding strength at high temperatures. It can be applied to a wide range of fields such as internal heat engines and large parts.

Claims (1)

[Claims] (1) Between the silicon nitride sintered bodies to be joined,
1 in a nitrogen atmosphere with an aluminum alloy containing 1 to 60% by weight of one or more group A metals.
A method for joining silicon nitride sintered bodies, the method comprising heating in a range of 000 to 1800°C.