JPS5983984A - Silicon nitride sintered body and metal bonding method - 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 The present invention relates to a method of joining a silicon nitride sintered body and a metal.

Silicon nitride sintered bodies have high heat resistance, high corrosion resistance, high insulation properties,
In addition, because it has many excellent features such as high wear resistance, its use as a material for structural parts of internal combustion engines, etc. is being considered, and technological development is active to improve the thermal efficiency and reduce weight of internal combustion engines. This is becoming more and more common. However, silicon nitride sintered bodies have the disadvantage of being relatively weak in mechanical impact and thermal shock, so it is better to use them in combination with metals than to use them alone to take advantage of each feature. Sometimes it can be advantageous to do so. Also,
There are some parts, such as a turbine rotor and an impeller for a turbocharger, that require heat resistance on one side, but not on the other. Therefore, a technology for joining silicon nitride sintered bodies and metals is essential. Conventionally, as a method for joining ceramics and metals, as shown in Fig. 81, for example, a cylindrical ceramic l and a cylindrical metal 2, there is a method in which a sleeve 3 is formed on the metal 2, and the ceramic 1 is fitted into the sleeve 3 and shrink-fitted.

However, in this shrink fitting method, the machining dimensional accuracy of the ceramic 1 and the sleeve 3 must be controlled to be ±51 Lm or less to obtain a strict interference margin, and the margin of error is too large. If the interference is too small, the joining strength will be reduced, so if the interference is too small, processing costs will increase.
If the two have the same diameter, it is necessary to provide a step 1a to reduce the diameter of the joint on the ceramic l side, which poses a problem in that this step 1a is likely to become a starting point for fracture.

-On the other hand, for oxide-based ceramics such as alumina ceramics, for example, a metallized layer is created on the ceramic surface using the Mo-Mn method, and after Ni coating is applied to protect the surface, the metal is removed. Although there are methods for joining silicon nitride sintered bodies metallurgically, the problem is that there is currently no established method for metallurgically joining silicon nitride sintered bodies.

The present invention was made in order to solve these conventional problems, and it is possible to obtain a silicon nitride sintered body-metal bonded body with good workability and excellent bonding strength. The purpose of the present invention is to provide a method for joining a quality sintered body and metal.

That is, the present invention provides an active metal or hydrogen of the active metal on one or both of the joint surfaces of the silicon nitride sintered body and the metal, and in one embodiment, mainly on the joint surface of the silicon nitride sintered body. This is a joining method characterized by applying a paste containing a compound and brazing the silicon nitride sintered body and metal at their joint surfaces.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 2 is a partially enlarged sectional view of a joint portion between a silicon nitride sintered body and a metal according to the present invention. When soldering the silicon nitride sintered body l and the metal 2, an active metal such as Ti,
Powder of Zr or its hydride is mixed with an organic solvent to form a paste 4, and this paste 4 is applied to the joint surface of the silicon nitride sintered body 1 with the metal 2. Next, a brazing filler metal 5 is interposed between the silicon nitride sintered body 1 and the metal 2, and the brazing filler metal 5 is heated in a non-melting atmosphere to a temperature higher than the melting point of the brazing filler metal 5, preferably 20 to 200°C or higher, and heated once. Brazing is performed by heating operation.

In this case, in order to obtain a sound bonded body, it is more preferable that the relative density of the silicon nitride sintered body 1 is 93% or more.

That is, - according to the implementation results, the relative density is 92.8%
If it is less than this, cracks will often occur in the silicon nitride sintered body l during soldering. Further, as the metal 2, the present invention can be applied to all iron-based alloys having a higher melting point than the brazing filler metal 5, and can also be applied to metals other than iron-based alloys. Furthermore, the active metals or their hydrides contained in the paste 4 have a weight ratio of 0.02 to 2
It is more desirable to set it to 0%. The reason for this is 0.02
If it is less than 20% by weight, Si in the silicon nitride sintered body 1 will be difficult to diffuse into the brazing filler metal 5, and sufficient bonding strength will not be obtained.On the other hand, if it exceeds 20% by weight, excess active metal will This is due to the fact that the bonding strength is reduced because it remains in the bonded portion.

Furthermore, the bonding method according to the present invention can be applied to active metals such as Ti.
, Zr or their hydrides are mixed in an organic solvent to form a paste, and by brushing or spraying, one or both of the bonding surfaces of the silicon nitride sintered body 1 and the metal 2, more preferably mainly silicon nitride. It is applied to the joining surface of the quality sintered body 1 and brazed.

Furthermore, in order to obtain strong bonding strength, the silicon nitride sintered body 1 must be held at a predetermined brazing temperature in an inert gas for a predetermined time so that the St in the silicon nitride sintered body 1 is sufficiently diffused into the brazing filler metal 5. It is desirable to do so. For example, when the brazing filler metal 5 is silver solder, it is preferable to heat and hold it at a temperature equal to or higher than the melting point of the brazing filler metal 5 for 10 minutes or more.

Next, examples of the present invention will be specifically described.

First, as shown in FIG. 3, a diameter 1 with a parallel portion 1b is
0 mm round bar-shaped silicon nitride sintered body 1 and parallel part 2
A round rod-shaped metal 2 having a diameter of 10mm and having a diameter of 10 mm and made of the material shown in Table 1 is prepared, and then the silicon nitride sintered body l and the metal 2 are bonded under the bonding conditions shown in Table 1. Each was soldered.

That is, in this example, Ti, Zr, TiH2, and ZrH2 each having a particle size of 200 mesh or less are individually mixed with an organic solvent to create a paste, and this paste is used to bond each silicon nitride sintered body 1. applied to the surface.

At this time, the coating amounts of T1, Zr, TiH2, and ZrH2 were determined to be the ratios shown in Table 1 to the brazing filler metal used. Next, a foil-shaped silver solder (JISBAg-7 (5) with a thickness of about 0.1
6%Ag-22%Cu-17%Zn-5%Sn) or BAg-8 (72%Ag-28%Cu) equivalent material) were stacked, and metal 2 was further abutted at the joint surfaces. Then,
As shown in Table 1, in a vacuum atmosphere (l 0-3tor
Brazing was performed in an inert atmosphere of 5% H2/N2 at the welding temperature and holding time shown in Table 1. Also, for comparison, TiH2 is used as an active metal.
Tests were also conducted on the case where the paste was applied with a brazing filler metal ratio of 0.01%.

The joints obtained by soldering under various conditions were subjected to a torsion test and observed using a scanning electron microscope. Table 2 shows the torsion test results for each bonded body test piece. At this time, the torsional strength was determined by performing a torsion test on three pieces of each joint and taking the average.
'Calculated using the following formula.

However, τ: torsional strength, T: torsional torque, as is clear from Table 2, the test piece N was soldered by the method of the present invention.
o, 1 to 5 all have torsional strength of approximately 8Kgf 7m
The area where the damage occurred was as high as m2 or more, and the ceramic part was the main body. On the other hand, Comparative Example No. 006 exhibited almost no torsional strength, and moreover, it deteriorated at the bonding interface. Therefore, according to the present invention, it is possible to obtain a joined body with excellent torsional strength.

The results of the analysis are shown in Figure 4, and the results of the component analysis are shown in Figure 5 (
Shown in a) and (b). As is clear from the figure, Si is diffused from the joint surface of the silicon nitride sintered body 1 to the layer of the brazing filler metal 5. This is thought to be due to Si3N4 reacting with Ti, and a reaction layer containing this Si is formed on the Si3N4 surface, which is presumed to be the cause of the strong adhesive force when bonded to the brazing material. Ru.

As described above, according to this embodiment, by applying a paste containing an active metal or a hydride of these to the joint surface of the silicon nitride sintered body, St from the silicon nitride sintered body is removed during soldering. diffusion is promoted, contributing to improved bonding strength.

FIG. 6 is a diagram showing another embodiment of the present invention, in which the present invention is applied to a turbocharger component. As shown in FIG. 6, the turbine impeller 11 on the high temperature side and the shaft 12 are integrally molded with ceramics, and the pressure on the low temperature side is rr6.
The impeller 14 and the impeller 14 are made of metal, for example, the impeller 13.
is made of aluminum, and the shaft 14 is made of 5US304. In this case, the impeller 13 and the metal shaft 14 are assembled by fitting the narrow diameter portion 15 provided on the metal shaft 14 into the compressor impeller 13 and fixing it with a nut 17 via a washer 16). It is. The metal shaft 14 is formed with a sleeve 18 having a tapered inner surface, and the ceramic shaft 12 is formed with a tapered protrusion 19 having the same taper shape as the tapered sleeve 18. A filler metal gap groove 19a is partially formed in the outer peripheral portion of the filler metal gap groove 19a.

When joining the ceramic shaft 12 and the metal shaft 14, a paste containing a mixture of an active metal hydride (TiHz) and an organic welding compound is applied to the brazing filler metal gap groove 19a of the Taber protrusion 19 of the ceramic shaft 12. After r+s L, insert the tapered protrusion 19 into the sleeve 18 of the metal shaft 14,
A brazing filler metal (BAg-
8) 21 was inserted. Next, soldering was carried out under the conditions of 850 DEG QX 15 min in a vacuum (10<-3 >torr or less). As a result, a sound joint was obtained.

As is clear from the above description, according to the present invention, after applying a paste containing an active metal or a hydride thereof to one or both of the joint surfaces of the silicon nitride sintered body and the metal, Since the silicon nitride sintered body and the metal are brazed at each joint surface, diffusion of S is promoted through the active metal at the soldered joint, resulting in a strong joint. It has become possible to obtain this, and its effects are remarkable.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional diagram of a bonded body formed by a conventional bonding method, Fig. 2 is an enlarged cross-sectional explanatory view of a joint between a silicon nitride sintered body and a metal according to the present invention, and Fig. 3 is a cross-sectional diagram of a bonded body according to the present invention. A perspective explanatory view of the silicon nitride sintered body and metal joined in the example, FIG. 4 is a microstructure photograph of the joint part of the joined body of FIG. 3, and FIG.
Figures (a) and (b) show the component distribution of 5i-Ti and 5i-Ti, respectively.
A photograph showing the component distribution of t-Cu and FIG. 6 are explanatory cross-sectional views of a turbine rotor and an impeller showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Silicon nitride sintered body, 2... Metal, 4... Paste, 5... Brazing metal, 12... Ceramic shaft,
14... Metal shaft, 21... Brazing metal. Patent applicant Yutaka Oshio, patent attorney representing Nissan Motor Co., Ltd.

Claims (1)

[Claims] (1) When joining a silicon nitride sintered body and a metal,
After applying a paste containing an active metal or a hydride of the active metal to one or both of the bonding surfaces of the silicon nitride sintered body and the metal, the silicon nitride sintered body and the metal are bonded. A method for joining a silicon nitride sintered body and a metal, characterized by surface brazing.