JPH063122B2 - Metal / ceramic composite and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal / ceramics composite and a method for producing the same. More specifically, the present invention relates to a metal / ceramics combined body in which a metal and a ceramics are combined by fitting and a method for manufacturing the same.

Ceramics are hard and have excellent wear resistance, as well as excellent mechanical properties and corrosion resistance at high temperatures, so they are suitable for rotors of gas turbines and turbochargers that require mechanical strength and wear resistance at high temperatures. Suitable as a structural material. For this reason, ceramics for gas turbine rotors and turbocharger rotors are being studied. For example, U.S. Pat. No. 4,396,445 discloses a turbine rotor having a structure in which blades and shafts are made of ceramics. In the turbine rotor of this structure, a screw portion is provided at one end of the ceramic shaft portion to fix the metal compressor impeller. However, the turbine rotor of this structure has a drawback that the screw part of the ceramic shaft is damaged during use of the turbine rotor due to the difference in thermal expansion between the metal material forming the compressor impeller and the ceramic material forming the shaft part. . Further, threading for ceramics requires a high level of technology, and has the drawback of being time-consuming and costly. As a countermeasure against this problem, Japanese Utility Model Laid-Open No. 57-92097 discloses a structure in which a ceramic shaft of a turbine rotor is fitted with a cylindrical portion provided at an end of a metal shaft. However, in this structure, in order to improve the wear resistance of the bearing contact portion on the surface of the metal shaft, when the ceramic shaft is fitted after the surface hardening treatment is performed on the surface of the metal shaft cylindrical portion, the surface hardening portion There is a drawback that cracking occurs. Further, when the surface of the metal shaft is subjected to a surface hardening treatment such as nitriding after the metal shaft and the ceramic shaft are fitted together, the tightening force of the fitting part may be reduced or the fitting part may come off. There is. Furthermore, if the metal shaft and the ceramic shaft are fitted together and then subjected to quenching treatment, there is a drawback that the fitting portion comes off due to phase transformation of the metal shaft due to quenching. Therefore, the above structure has a drawback in that the bearing contact portion on the surface of the metal shaft portion has insufficient wear resistance and is not practical.

It is an object of the present invention to provide a metal / ceramic composite body having a large bonding force and a large wear resistance at a predetermined position of a metal portion, and a method for producing the same.

The features of the present invention are as follows.

1st invention A convex portion provided on a ceramic member is shrink-fitted to a concave portion provided on a metal member having a hardened zone and an uncured zone on its surface,
In a metal-ceramic combined body having a structure that is joined by an interference fit such as press fit, a hardened zone and a non-hardened zone are present on the outer surface of the recess, and the deformation area of the metal member due to the interference fit is not A metal / ceramic bonding body, characterized in that the deformation zone is within 1 mm or more from the boundary of the hardening zone while being within the hardening zone.

Second invention Metal / ceramics in which a convex portion provided on a ceramic member is joined to a concave portion provided on a metal member whose surface is partially hardened by shrink fitting, cold fitting, press fitting, or the like. In the method of forming a combined body, the metal member is provided with a recess,
After that, of the outer surface of the metal member, the surface of a portion of the outer surface of the recess forming portion that is 1 mm or more away from the area to be deformed by the above interference fit is subjected to a surface hardening treatment, and then the recess is provided on the ceramic member. The convex portions are joined by an interference fit so that the deformation area of the metal member due to the interference fit is in the non-surface hardening zone and the deformation area is separated from the hardening zone boundary by 1 mm or more. Method for producing combined metal / ceramics.

In the present invention, the metal member and the ceramic member are joined by fitting the convex portion provided on the ceramic member into the concave portion provided on the metal member whose surface is partially hardened. This surface hardening treatment is carried out at least when the metal / ceramics bonded body of the present invention is used, where the metal portion constituting the bonded body is abraded by friction or sliding of other machine parts. By this surface hardening treatment, a hardened layer is formed on the surface of the metal member, and the wear resistance of a specific portion of the metal portion of the metal / ceramics composite of the present invention is improved. As the surface hardening method, methods such as carburizing, nitriding, surface hardening, discharge hardening, and plating can be used. Of these surface hardening treatment methods, a surface hardened layer that is thick in carburization, nitriding and surface hardening can be obtained, which is preferable. Of the various nitriding methods, the ion nitriding method is particularly preferable because the area and the hardening depth of the surface hardened portion can be easily adjusted.

On the other hand, when the protrusions on the ceramics member and the recesses on the metal member are connected by fitting, the fitting causes deformation in the recesses in proportion to the size of the interference. However, since the surface hardened layer is brittle and cannot be plastically deformed, when the surface hardened portion is plastically deformed by fitting, cracks are generated in the surface hardened layer. For this reason, in the metal / ceramics combination of the present invention, such deformation of the metal member occurs in the non-hardened zone of the metal member. In this case, a space of at least 1 mm is provided between the deformed portion and the surface hardened zone. The size of this interval is set when the metal member is deformed by fitting.
As long as the surface hardening portion of the metal member does not cause defects such as cracks due to the influence of the deformation, it is sufficient that this interval is the processing accuracy of the ceramic member and the metal member, the fitting method of both members, and the metal member. It is determined according to the amount of deformation and the shapes and dimensions of both members.

For example, when fitting a convex portion of 7.0 mm in diameter provided on a ceramic member into a concave portion of 6.8 mm in inner diameter provided on a metal member having a diameter of 9.3 mm, between the deformed portion of the metal member and the surface hardened zone. It is necessary that at least 1 mm or more is provided between, and 2 mm or more is particularly preferable. If this distance is 2 mm or more, it is not particularly necessary to make the processing accuracy of both member fitting parts and the positioning accuracy of the surface hardened zone particularly high, which is particularly preferable. However, if this interval is 1 mm or less, it is not preferable because it is necessary to make the processing accuracy of both member fitting portions and the positioning accuracy of the surface hardening zone particularly high. The upper limit of the interval may be appropriately determined in consideration of the position of the portion requiring wear resistance on the metal member surface and the position of the deformed portion due to fitting, but the position and area of the surface-hardened portion Is determined to be equal to or greater than the position and area of the portion requiring wear resistance on the surface of the metal member. As a result, the surface / hardness of the predetermined portion of the metal portion is large, and the metal / ceramics bonded body of the present invention having no defects in the bonded portion can be obtained.

The metal member forming the metal / ceramics combined body of the present invention and the ceramic material can be fitted together by any of shrink fitting, cold fitting, and press fitting. Shrink fit and cold fit process the protrusion diameter on the ceramic member to be larger than the inner diameter of the recess on the metal member, heat or cool one of the fitted members, and insert a dimensional difference between both members. This is a preferable method for fitting a metal / ceramics combination body having a large fitting portion size because the two members are fitted together by utilizing the difference in size. In addition, since a metal material generally has a larger coefficient of thermal expansion than a ceramics member, a shrink fit for heating a metal member can obtain a large dimensional difference with a small temperature difference, and a stable shrink fit operation can be performed. It is preferable. In this case, the shrinkage margins of shrink fit and shrink fit do not damage the concave portion of the metal member and the convex portion of the ceramic member after fitting, and the fitting portion is not affected by the use condition of the metal / ceramics combined body of the present invention. The size should be such that the required tightening force can be obtained.

On the other hand, the press-fitting is such that the convex portion on the ceramics member is loaded on a concave portion having a diameter smaller than the diameter of the convex portion provided on the metal member,
This is a method of forcibly pushing in and fitting. Since the dimensional difference between the diameter of the convex portion and the inner diameter of the concave portion is absorbed by the elastic deformation and plastic deformation of the metal member, the finish dimensional tolerance of the convex portion and the concave portion before press-fitting is gentler than that in the case of shrink fitting and shrink fitting. Good.
Therefore, the press-fitting is more preferable as a method of fitting a metal / ceramics combined body having a small fitting portion size. The shape and dimensions of the recesses on the metal member and the protrusions on the ceramic member are such that they will not be destroyed by the load acting during press fitting. Further, the dimensional difference between the diameter of the convex portion and the inner diameter of the concave portion is such that the fitting portion has a tightening force according to the usage conditions of the metal / ceramics combined body of the present invention, and both the convex portion and the concave portion during press fitting. The size should not be destroyed. For this purpose, the dimensional difference between the convex portion on the ceramic member and the concave portion on the metal member is such that the diameter of the convex portion is 1% of the inner diameter of the concave portion.
Preferably 10% to 10% larger, 1% to 5%
It is more preferable to increase the size. If this dimensional difference is 1% or less, the tightening force of the press-fitting portion will be insufficient, and the fitting portion due to the press-fitting may come off during use, which is not preferable. 10 dimensional difference
If it is more than 0.1%, the load required for press-fitting becomes too large, and the convex portion on the ceramics member is destroyed during press-fitting, which is not preferable. This press-fitting may be performed at room temperature, or only the metal member may be heated, or both the metal member and the ceramic member may be heated and press-fitted. However, it is preferable to have a method of heating both members and press-fitting them. What happens is that when both members are heated, the deformation resistance of the metal member decreases, and the load required for press fitting decreases, so damage to both members during press fitting does not occur, and both members are cooled during cooling from the press fitting temperature. This is because the tightening force increases due to the difference in thermal expansion between the two. When both members are heated and press-fitted, the press-fitting temperature is preferably lower than the annealing temperature of the metal member or the softening temperature of the surface-hardened layer, whichever is lower, and more than the working temperature of the press-fitting part. When the press-fitting temperature is higher than the annealing temperature of the metal member, the internal stress generated in the metal member is relieved and the tightening force of the press-fitting portion is reduced, which is not preferable. Further, if the press-fitting temperature is higher than the softening temperature of the surface-hardened layer, the effect of the surface-hardening treatment decreases, which is not preferable. Furthermore, when the press-fitting temperature is lower than the operating temperature of the press-fitting part, when the temperature of the press-fitting part rises to the operating temperature, the thermal expansion of the metal member is generally larger than the thermal expansion of the ceramics member, so the press-fitting part is loosened and tightened. It is not preferable because the attaching force is reduced.

The metal / ceramics combined body of the present invention is usually used after being subjected to finishing after fitting the metal member and the ceramic member. Therefore, it is necessary for a metal portion that requires wear resistance during use to exhibit a predetermined surface hardness even if the surface is ground by finishing. However, the hardness of the surface of the metal member and the change in the hardness from the surface of the metal member to the inside due to the surface hardening treatment are variously changed depending on the type of metal material forming the metal member, the size and conditions of the surface hardening. For this reason, the amount of surface grinding in the finishing process of the metal part that requires wear resistance during use is determined according to the predetermined surface hardness, the type of metal material forming the metal member, and the method and conditions for surface hardening. . Alternatively, the type of metal material forming the metal member and the method and conditions for surface hardening are determined according to the amount of finish grinding and the surface hardness of the metal portion.

As the metal material forming the metal / ceramics composite of the present invention, a commercially available metal material that can be surface hardened by a method such as carburizing, nitriding, surface quenching, discharge hardening, and plating is used. For example, when surface hardening is performed by nitriding, an iron alloy containing chromium such as stainless steel, alloy tool steel, chrome molybdenum steel, and aluminum chrome molybdenum steel, and an alloy containing titanium and zirconium and these elements are preferable. When surface hardening is performed by ion nitriding, aluminum chrome molybdenum steel and stainless steel are more preferable because they have high surface hardness and are hardened from the surface to a deep position, and aluminum chrome molybdenum steel is also preferable because it is inexpensive. .

The ceramic material constituting the metal / ceramics composite of the present invention is selected from silicon nitride, silicon carbide, zirconia, alumina, beryllia, sialon, etc. according to the purpose of use of the metal / ceramics composite of the present invention. For example, when a turbocharger rotor or a gas turbine rotor is made of the metal-ceramics combination of the present invention, the turbine wheel that is exposed to the high temperature of exhaust gas and that rotates at high speed and the rotating shaft that follows it have high high temperature strength. ,
Silicon nitride having a small specific gravity is preferable.

FIG. 1 shows a metal for explaining Examples 1 to 3 of the present invention.
It is a fragmentary sectional view of a ceramics combination. An embodiment will be described below with reference to FIG.

Example 1) Silicon nitride manufactured by an atmospheric pressure sintering method (hereinafter referred to as silicon nitride)
A ceramic member 10 having a shape shown in FIG. 1 having a convex portion 11 having a diameter of 7.0 mm and a length of 25 mm was produced from a round bar. In addition, an aluminum chrome molybdenum steel (JIS-SACM645, hereinafter referred to as nitrided steel) round bar with a diameter of 9.3 mm, which has a recess 21 with an inner diameter of 6.8 mm and a depth of 15 mm at one end, has the shape shown in FIG. The metal member 20 was produced. Next, the section up to the position 17 mm away from the recessed inlet side end surface of the metal member is covered with a mild steel cover, and the outer surface of the remaining portion (section A in Fig. 1) is treated with an equal amount of nitrogen at a pressure of 4 Toor. In a mixed atmosphere composed of hydrogen, a metal member (referred to as metal member A) subjected to ion nitriding treatment for 20 hours while being heated to 550 ° C., and the entire outer surface of the metal member (see FIG. 1B).
A metal member (referred to as metal member B) was produced by subjecting the section) to the ion nitriding treatment under the same conditions as the metal member A.

By the ion nitriding treatment under the above conditions, the Vickers hardness of the surface of the nitrided portion of the nitrided steel increased from Hv (0.1) 200 before nitriding treatment to Hv (0.1) 1100. Also, 0.2 from the surface
Vickers hardness at a depth of mm is Hv (0.1) 700
showed that.

The protrusions 11 of the ceramics member were press-fitted into the recesses 21 of the above-mentioned two kinds of metal members 20 at 350 ° C. to produce a metal / ceramics combined body having the shape shown in FIG. Due to this press-fitting, a section from the entrance of the concave portion of the metal member to a depth of 13 mm (first
The section (C in the figure) was deformed, and the diameter of the metal part was increased by about 0.2 mm. When the outer surface of the deformed portion of the metal member due to this press-fitting was inspected, no abnormality was found in the metal / ceramics combined body using the metal member A. In the metal / ceramics combined body using the metal member B, many cracks having a length of about 10 mm and a depth of about 0.5 mm were detected along the axial direction of the metal member.

As described above, when the surface hardened portion of the metal member is deformed by press fitting, cracks are generated on the surface of the metal member, and a sound metal / ceramics combined body cannot be obtained. On the other hand, in the metal / ceramics combined body of the present invention which uses the metal member A whose surface is not hardened by the press-fitting deformation, even if the metal member is deformed by the press-fitting, no crack is generated on the surface of the metal member.

Example 2) A ceramic member and a metal member having the same material and shape as those of Example 1 were produced. About this metal member, the outer surface of the section up to the positions 13.5 mm (referred to as metal member C), 14.5 mm (referred to as metal member D), and 15.5 mm (referred to as metal member E) from the end surface on the concave side is made of mild steel. Three types of metal members were produced, which were covered with a cover made of metal and subjected to ion nitriding treatment on the outer surface of the remaining section under the same conditions as in Example 1. The recesses of the ceramic member were press-fitted into the recesses of these three types of metal members at 350 ° C. to produce a metal / ceramics bonded body having the shape shown in FIG. By this press-fitting, each metal member was deformed in a section up to a position 13 mm away from the end surface on the concave side, and the outer diameter was increased.
When the outer surface of the deformed portion of the metal / ceramics combined body by press fitting of the metal portion and its peripheral portion was inspected, no cracks were found on the outer surface of the metal members D and E. However, in the vicinity of the boundary between the ion-nitrided portion and the non-nitrided portion of the metal member C, the length of about 2 mm and the depth of about 0.2 m along the axial direction of the metal member.
A crack of m has been detected. As described above, in the metal / ceramics combined body of the present invention in which the deformation area of the metal member due to the press-fitting and the surface hardened area of the metal member are separated by a predetermined distance or more, even if the deformation of the metal member occurs due to the press-fitting, the metal member surface No cracks occur.

Example 3) From a silicon nitride round bar, the diameter is shown in Table 1 and the length is 25 mm.
A ceramic member having the shape shown in FIG. Also, from annealed nitrided steel round bar, diameter 9.
A test piece having a length of 3 mm and a length of 80 mm was prepared, and a section up to a position 15 mm away from one end of the test piece was covered with a mild steel cover, and the surface of the remaining portion was cured by ion nitriding under the same conditions as in Example 1. . After that, a first recess having a diameter shown in Table 1 and a depth of 15 mm is formed at the end on the non-cured portion side of the test piece.
A metal member having the shape shown in the figure was produced. The convex portion of the ceramic member is press-fitted into the concave portion of the metal member at 350 ° C.
A metal / ceramics composite having the shape shown in the figure was produced.
Next, after the screw 22 having a predetermined size is processed on the end of the metal member, the jig shown in FIG. 2 is used to put the portion shown in FIG. The member and the metal member were vertically pulled out, and the load required for pulling out the press-fitting portion was measured. The obtained results are shown in Table 1.

Among the results shown in Table 1, No. 1 to No. 6 are metal / ceramics combined bodies in which the dimensional difference between the convex portion diameter on the ceramic member and the concave portion inner diameter on the metal member is the size of the present invention. No. 10 to No. 12 are metal-ceramics combined bodies in which the dimensional difference is outside the scope of the present invention. As is clear from Table 1, the above-mentioned dimensional difference is the size of the present invention.
The ceramic composite shows a large pulling load at 350 ° C. On the other hand, the metal / ceramics combined body having the dimensional difference equal to or less than the size of the present invention has a small drawing load. Further, in the metal / ceramics combined body having the dimensional difference larger than that of the present invention, the convex portion of the ceramics member is damaged during press fitting.

Example 4) A turbine wheel 41 having a diameter of 61 mm and a turbine shaft 42 having a diameter of 9.1 mm are integrally molded of silicon nitride to have a total length of 6
A 0 mm ceramic member 40 was produced. A diameter of 6 mm and a length of 13 mm are attached to the tip of the turbine shaft of this ceramic member.
The mm convex portion 43 was processed. Also, total length 70 mm, diameter 9.1 m
A m-nitride steel round bar was prepared, a section from the one end to a position 13 mm apart was covered with a mild steel cover, and the surface of the remaining part was cured by ion nitriding treatment under the same conditions as in Example 1. Next, at the end of the round bar on the non-nitriding side, a diameter of 5.8 m
A metal member 50 was manufactured by processing the recess 52 having a depth of 12 mm and a depth of 12 mm. The convex portion 43 at the tip of the turbine shaft is provided in the concave portion 52 at 350 ° C. which is a temperature higher than the working temperature of the fitting portion.
By press fitting with the ceramic member 40 and the metal member 50.
After they are integrally connected, the ceramic turbine shaft 42 and the metal turbine shaft 51 are machined to have a diameter of 9.0 mm and the rotary shaft 58 on the compressor wheel side is machined to have a diameter of 5 mm. A turbocharger rotor was manufactured in which a part of the above was made of silicon nitride and the remaining part was made of nitrided steel. This turbocharger rotor was installed in a high-temperature rotation tester and a rotation test was carried out at 150,000 rpm for 1 hour using combustion gas. No abnormality was found in the fitting portion and the bearing contact surface 54 of the metal turbine shaft. It was

As is clear from the above description, the metal / ceramics combined body of the present invention is provided with a convex portion having a diameter 1% to 10% larger than the inner diameter of the concave portion provided in the concave portion provided in the metal member having the predetermined portion surface-hardened. Since they are fitted and integrally joined, the joining strength is high and the wear resistance of a predetermined portion of the metal portion is excellent. Therefore, the metal of the present invention
By constructing a turbocharger rotor that consists of ceramic wheels, part of the turbine wheel and turbine shaft is silicon nitride, and the other part is nitrided steel, a highly efficient turbocharger with excellent responsiveness and durability. can do.

As described above, the metal / ceramics combined body of the present invention is a structure that receives the high temperature and repetitive load of engine parts such as turbocharger rotor and gas turbine rotor by taking advantage of the heat resistance, wear resistance, and high strength of ceramics. It has an advantage that it can be used as a body part and can be provided at low cost and with excellent durability.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a metal / ceramics bonded body for explaining an embodiment of the present invention, FIG. 2 is an explanatory view showing a method of pulling out a metal / ceramics bonded body, and FIG. 3 is a view of the present invention. It is explanatory drawing which shows the longitudinal cross-sectional view of the press fit fitting part of the turbocharger rotor of the specific application example of a metal / ceramics coupling body. DESCRIPTION OF SYMBOLS 10 ... Ceramic member 11 ... Convex part on ceramic member 20 ... Metal member 21 ... Recess on metal member 22 ... Screw 30 ... Pull-out test pull rod 31 ... Pull-out test tool 40 ... Ceramic member 41 ... Ceramic turbine wheel 42 ... Ceramics turbine shaft 43 ... Convex portion on ceramics turbine shaft 50 ... Metal member 51 ... Metal turbine shaft 52 ... Recessed portion on metal turbine shaft 58 ... Rotor shaft on compressor wheel 54 ... Bearing contact surface

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-58-217814 (JP, A) JP-A-54-42520 (JP, A) JP-A-59-13678 (JP, A) JP-A-58- 61269 (JP, A) Actually opened 59-9102 (JP, U) Actually opened 57-92097 (JP, U)

Claims (8)

[Claims] 1. A convex portion provided on a ceramic member is joined to a concave portion provided on a metal member having a hardened zone and an uncured zone on the surface by shrink fit, shrink fit, press fit, or the like. In the metal / ceramic composite having the structure, there are a hardened zone and a non-hardened zone on the outer surface of the recess, and the deformation area of the metal member due to the interference fit is within the non-hardened zone, and the deformation area is A metal / ceramic composite characterized by being separated by 1 mm or more from the boundary of the hardening zone. 2. The metal / ceramic bonding article according to claim 1, wherein the hardening zone is ion-nitrided. 3. The metal / ceramic bonding body according to claim 1, wherein the metal member is made of nitrided steel and the ceramic member is made of silicon nitride. 4. A metal-ceramic combined body which is a turbocharger rotor.
Item 8. A metal / ceramic composite body according to any one of items. 5. A metal formed by shrink-fitting a convex portion provided on a ceramic member into a concave portion provided on a metal member whose surface is partially hardened by shrink fitting, cold fitting, press-fitting, or the like.・
In the method of forming a ceramics combined body, a concave portion is provided in a metal member, and then, from the outer surface of the metallic member, the outer surface of the concave portion-forming portion is to be deformed by the above-mentioned interference fit to 1
After surface hardening treatment on the surface of the part that is more than mm away,
The convex portion provided on the ceramic member is coupled to the concave portion by an interference fit so that the deformation area of the metal member due to the interference fit is within the non-surface hardening zone and the deformation area is 1 mm from the hardening zone boundary.
A method for producing a metal / ceramic composite body, characterized in that they are separated as described above. 6. The method for producing a metal / ceramic bonding body according to claim 5, wherein the hardening treatment is ion nitriding. 7. The method according to any one of claims 5 to 6, wherein the fitting is press-fitting at a temperature not higher than an annealing temperature of the metal member and at a temperature higher than a room temperature or a maximum working temperature of the fitting portion. Method for manufacturing metal / ceramic composites. 8. The metal / ceramic bonding article according to claim 5, wherein the diameter of the convex portion on the ceramic member is 1% to 10% larger than the inner diameter of the concave portion on the metal member. Manufacturing method.