JPH0489366A - Production of functionally gradient material - Google Patents

Abstract

PURPOSE:To obtain a functionally gradient material which is high in interface strength and free from deterioration of characteristics due to unnecessary heating and also free from action of residual stress at a time of utilization by sputtering the surfaces of molded mixing bodies at high vacuum at ordinary temp. and previously heating the surfaces and thereafter joining them. CONSTITUTION:In a method for producing the functionally gradient material in which the mixing bodies of a plurality of kinds of substance are laminated in the thickness direction and the mixing ratio thereof is stepwise changed, the following means is adopted. In other words, the surfaces of the molded mixing bodies 11, 12 are sputtered (an Ar atomic beam generator is shown in 4) at high vacuum at ordinary temp. and previously heated (only one side of mixing body 12 is heated by a laser heating source 5). Then the mixing bodies 11, 12 are pressurized and joined instantaneously after heating. Then a mixing body 13 is joined to the joining body of the mixing bodies 11, 12 by the same method. Thereafter the above-mentioned processes are successively repeated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a functionally graded material.

[Conventional technology]

Functionally graded materials have a composition gradient from one side to the other.
It is, for example, a plate-shaped material with graded functions, and a layer whose composition changes continuously or stepwise is interposed between the negative side and the other side.

The manufacturing method is PVD. C. Ikeno: Proceedings of the 2nd Symposium on Functional Gradient Materials, (1988) P
There is a method of continuously changing the composition ratio using I3) and CVO (Sasaki et al.: Proceedings of the 3rd Functionally Gradient Materials Symposium, (1989) P61), but the maximum thickness is about 21TII11.

Examples of methods for manufacturing a functionally gradient material having a thickness of several inches are as follows. Kawasaki et. A functionally gradient material was produced by laminating, molding, and sintering. Furthermore, Tsutsumi [Proceedings of the 2nd Symposium on Functionally Gradient Materials, (1988) P39] reported that Mo powder and Si
A mixed powder of SiJ and SiJ (mixing ratio: 6:4) was stacked and filled into a container while changing the mixing ratio stepwise, and the mixture was then molded and sintered.

[Problem to be solved by the invention]

In the above-described embankment manufacturing method, residual stress was generated due to dimensional changes in the mixture due to sintering, resulting in cracks. Kawasaki et al.'s manufacturing method was able to prevent the occurrence of cracks and peeling of the interface of the mixture through optimal design, but calculations showed that even in that case, residual stress of approximately 200 MPa was generated in the thickness direction. Ta. If such residual stress exists, there is a risk that the interfacial strength of the mixture will decrease.

Also, when sintering a powder mixture with a stepwise change in mixing ratio, or when joining already sintered materials, the whole is heated uniformly, but depending on the mixture, the heating temperature may be too high. However, undesirable chemical changes could occur and the properties of the mixture could be impaired. For example, if thermal spraying alone is used as a molded product, voids peculiar to thermal spraying will disappear, which is inconvenient.

The present invention has been made in view of the above circumstances, and by sputtering the surface of the molded mixture at room temperature in a high vacuum and heating it in advance before joining, the interfacial strength is high and unnecessary The purpose of the present invention is to provide a functionally graded material whose properties are not impaired because it is not subjected to severe heating (and which is free from residual stress during use).

[Means to solve the problem]

The method for producing a functionally graded material according to the present invention is a method for producing a functionally graded material in which a plurality of mixtures of a plurality of substances are laminated in the thickness direction, and the mixing ratio thereof changes stepwise. It is characterized in that the surface of the mixture is sputtered in a high vacuum at room temperature, heated in advance, and bonded sequentially.

[Function] In the room temperature bonding method, the surfaces to be bonded are sputtered in a high vacuum, so the surfaces are cleaned and surface layer atoms are activated, so bonding can be easily performed at room temperature. Therefore, the properties of each mixture constituting the functionally-gradient material are not impaired because it is possible to join without heating the whole body to a high temperature.

The strength of the interface of the bonded mixture increases.

In addition, in order to prevent residual stress from acting at the actual operating temperature of the functionally graded material, the temperature at which one of the mixtures should be heated is determined, and the mixture is heated before joining, which prevents the generation of residual stress. It can be prevented. Furthermore, the heating temperature at this time is lower than the temperature during sintering as well as the temperature at which it is actually used, so that the interface to be joined will not be contaminated by the formation of oxides or the like.

[Example] The present invention will be explained in detail below.

The rate of change in the mixing ratio of adjacent mixtures should be 10% or less, and 1
Each mixture in which the mixing ratio is changed over 0 stages is molded into a desired size and thickness. At this time, in order to increase the adhesion area during bonding, each mixture is subjected to mechanical polishing and electrolytic polishing to remove compressive residual stress and improve flatness.

FIG. 1 is a schematic diagram showing the implementation state of the method of the present invention. In the figure, reference numerals 1 and 2 are mixture holding stands installed in the vacuum chamber, and a recess approximately the same size as the mixture is provided on the upper surface of the stand, and the recess is held by a fixing member such as a screw. It is constructed so that it can hold the mixture at

The mixture holding tables 1 and 2 are connected by a rotation introduction terminal 3 having a hinge structure. Rotating rods (not shown) are connected to the mixture holding tables 1 and 2, respectively, and the rotating rods are drawn out of the vacuum chamber. Therefore, the rotation introduction terminal 3 and the rotation rod allow the mixture holding table 1.2
can be rotated so that the respective recesses face each other.

At the top of the vacuum chamber is an Ar atomic beam generator 4.4.
is movably provided, and when the mixture holding tables 1 and 2 are fixed with their respective recesses facing upward,
It is moved above the mixture holding table 1.2.

A laser heating source 5 is also movably provided at the top of the vacuum chamber, and when the mixture holder 2 is fixed with its recess facing upward, the laser heating source 5 is provided above the mixture holder 2. will be moved.

When joining using a device configured in this way,
As shown in FIG. 1 (a), fix the mixture holding tables 1 and 2 with their respective recesses facing upward, and place the mixture 11 in the recess of the mixture holding table 1. Mixture 1 in the recess of stand 2
Hold 2.

Then, the inside of the vacuum chamber is under high vacuum (~107 Torr).
Make it. At this time, the Ar atomic beam generator 4.4 is moved above the mixture holders 1 and 2, and the upper surface of the mixture 11 held on the mixture holder 1 and the mixture 11 held on the mixture holder 2 are moved. The upper surface of the mixture 12 is irradiated with an atomic beam to perform sputtering.

Next, as shown in FIG. 1(B), the laser heating source 5 is moved above the mixture holding table 2, and the mixture 12 held on the mixture holding table 2 is irradiated with the laser and heated. .

Immediately after heating, the mixture holder 2 is rotated to match the mixture holder 1 as shown in FIG. 1(c), and the mixture 11 and the mixture 12 are joined together and lightly pressurized.

Then, as shown in FIG. 1(d), the mixture 13 to be joined next is held on the mixture holder 2, and the above-mentioned steps are repeated.

Regarding the heating shown in Figure 1 (b), it is desirable to heat both mixtures to be joined to the working temperature in order to prevent the effects of residual stress at the working temperature, but if heated to a high temperature, a high vacuum state will occur. This is also undesirable because the bonding interface becomes dirty.

Therefore, in the present invention, one of the mixtures is heated, and the heating temperature is determined as follows.

Figure 2 is a diagram showing changes in the length of two materials A and B, (a) is a diagram showing the length at room temperature, and (b) is a diagram showing the length at operating temperature. It is.

In the second lesson (a), the lengths of materials A and B are a and b, respectively.
It is. Let the coefficients of linear expansion of the two materials A and B be α and β(α
〉β), then at the operating temperature (room temperature + ΔT) shown in Figure 2 (C), the lengths of materials A and B are a(1+α).
・ΔT, ,), b(1+β・ΔT,).

When these materials A and B are joined, assuming that the lengths of materials A and B are equal at the operating temperature, a(1+α・ΔTr)−b(1
+β・ΔT, ), so the following formula (1) % formula %Here, we will heat only A to make the length of A equal to the length b of B, and if this heating temperature is ΔT, then the following formula ( 2
) holds true.

a(1+α・ΔT)−S formula (+), by eliminating a/b from (2), ΔT is expressed as.

For example, a mixture of zirconia ceramics ZrO□・3YzO3 and stainless steel is mixed so that the weight component ratio of ZrO□・3Y20:l changes from 100% to 0% in 10% increments, and these are joined. temperature 500°
When used in C, the coefficient of linear expansion of ZrO□・3Y203 and stainless steel is 1.3 to IXl0-5, respectively.
Considering that X10-5, the temperature ΔT at which each mixture should be heated when bonding is calculated from 2 (3).
The temperature is about 10°C for both mixture junctions.

Therefore, before joining, the mixture having a higher weight component ratio of stainless steel may be heated to a temperature 10° C. higher than room temperature.

By heating one of the mixtures at a low temperature as described above, it is possible to prevent residual stress from acting at high operating temperatures.

[Numerical Example] A specific example in which a functionally gradient material was manufactured using stainless steel 511S316, zirconia ceramic, and Cuc Zr0z.3Y20:1 will be shown below.

ZrO□・3Y203 powder with an average particle size of 0.18 μm and stainless steel-like powder with an average particle size of 3 μm were mixed into ZrO□・3Y
The weight component ratio of ZO3 was mixed in 10% increments from 100% to 0%, and 100 tons of each mixture was mixed.
After molding with a mold at 1Pa, cold isostatic molding was performed at 200MPa. At this time, ZrO□・3Y
The thickness of the 20:1 pure product and the pure stainless steel product are 2 and 5 strokes, respectively, and the thickness of the intermediate mixture is 1.5 strokes, respectively.

Next, mechanical polishing and electrolytic polishing were performed to flatten the surface of each mixture.

The mixture to be bonded was then held on a mixture holder 1.2 in the vacuum chamber shown in FIG.

At this time, the ZrO□.3Y203 mixtures are held on the mixture holding table 1.2 in order of increasing weight component ratio.

The pressure inside the vacuum chamber was set to 10-'Torr, and the surface of the mixture to be joined was heated with an Ar atomic beam generator 4.
．． Sputtering was performed using 4.

Next, the mixture held on the mixture holding table 2 was irradiated with an infrared laser from the laser heating source 5 and heated to a temperature 20 to 30°C higher than room temperature. At this time, the heating temperature determined by the above calculation was lo'c higher than room temperature, but when actually joining, the length of the mixture that was not heated was slightly longer due to the joining of the previous mixture. Taking this into consideration, we set the temperature to 20 to 30°C higher than room temperature.Then, we bonded immediately after heating, and the bonding temperature was approximately 10 kg f/mm.
The pressure was applied for approximately 5 minutes.

After the joined mixture has sufficiently cooled, the next mixture to be joined is held on the mixture holding table 2, and the above-mentioned operation is repeated.

As a comparative example, bonding was performed without heating by the laser heating source 5 after sputtering.

Furthermore, bonding was also performed using a conventional method. ZrO□・3Y
2(h powder and stainless steel powder, Zr(h ・3Y
The weight component ratio of zOt is mixed in 10% increments from 100% to 0% and laminated sequentially, making the whole 100%
After molding with a mold at MPa, cold isostatic molding was performed at 200 MPa. and I X 10-'T
Sintering was carried out at 1350° C. for 1 hour under a pressure of orr.

A tensile test was conducted to evaluate the tensile (adhesion) strength of the functionally gradient materials produced by the method of the example, the method of the comparative example, and the conventional method. FIG. 3 shows a longitudinal sectional view showing the state in which the tensile test was carried out.

In FIG. 3, reference numeral 21.21 indicates a jig, and the test material 22 is held between the jigs 21, 21 with an adhesive layer 23.23 interposed therebetween. In this test, the test material 22 is pulled vertically using jigs 21, 21, and the pressure at which the test material breaks is determined. The results of this test are shown in FIG.

Figure 4 shows that the functionally graded material manufactured by the method of the example has improved tensile strength compared to the material manufactured by the conventional method, and the material manufactured by the method of the example is different from the material manufactured by the method of the comparative example at room temperature. It can be seen that although the tensile strength is inferior to that of the other materials, it is superior at the operating temperatures of 300°C and 500°C. Therefore, it has been proven that the functionally graded material produced by the method of the present invention prevents the generation of residual stress at the operating temperature and therefore has high interfacial strength.

In the above-mentioned example, the case where a plate-shaped material is manufactured as a functionally graded material is explained, but the present invention is not limited to this in any way, and may be applied to materials of other shapes such as a columnar shape. Needless to say.

[Effects] As described above, the functionally graded material produced by the method of the present invention is sputtered on the surface of the molded mixture at room temperature in a high vacuum, and is heated beforehand before being bonded, so that the interface of the bonded mixture is It has high strength and is not heated to high temperatures, so the properties of each mixture are not impaired. Further, it has excellent effects such as no residual stress acting at the temperature actually used.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing how the method of the present invention is carried out, Fig. 2 is a diagram showing changes in the length of two materials, Fig. 3 is a longitudinal cross-sectional view showing how a tensile test is carried out, and Fig. 4 is a diagram showing the results of a tensile test. 1.2... Material holding stand 3... Rotation introduction terminal 4...
・Atomic beam generator 5-... Laser heating source Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney
Noboru Kono C) Fig. Room temperature operating temperature (room temperature + ΔTr) (A) (B) Fig. Fig. (C) Fig.

Claims (1)

[Claims] 1. In a method for manufacturing a functionally graded material in which a plurality of mixtures of a plurality of substances are laminated in the thickness direction and the mixture ratio thereof changes stepwise, the surface of the molded mixture A method for manufacturing a functionally graded material, which comprises sputtering the following in a high vacuum at room temperature, heating in advance, and sequentially bonding.