Method of manufacturing laminate and laminate

A method of manufacturing a laminate in which a spray coating film made of a material different from a base material is laminated on the base material includes: a base material heating step of heating the base material; an intermediate layer forming step of forming, on a surface of the heated base material, an intermediate layer made of a material different from the base material and the spray coating film; and a spray coating film forming step of forming the spray coating film on a surface of the intermediate layer.

FIELD

The present invention relates to a method of manufacturing a laminate in which a spray coating film is laminated on a base material, and a laminate.

BACKGROUND

A laminate obtained by laminating a material different from the base material on the base material is used for various applications depending on the combination of materials. For example, the laminate obtained by laminating ceramic or cermet on an aluminum base material by thermal spraying is used for a substrate supporting device or a stage heater which adjusts the temperature of the semiconductor substrate in a semiconductor manufacturing process.

Meanwhile, when a thermal expansion coefficient of the base material is different from a thermal expansion coefficient of the spray coating film formed on the base material, if the base material is heated during use of the laminate, crack may occur in the spray coating film due to stress. In order to suppress an occurrence of such a crack or increase the temperature at which the crack begins to occur, a technique of alleviating the stress by providing a material having a thermal expansion coefficient between the base material and the spray coating film or a porous material having low rigidity as an intermediate layer has been known. Further, Patent Literature 1 discloses a technique of suppressing an occurrence of tensile stress in the spray coating film when heating the base material, by performing the thermal spraying on a plate portion serving as the base material at a work temperature which generates the residual stress at which the crack does not occur in actual use temperature of the substrate supporting device.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

According to the technique disclosed in Patent Literature 1, it is possible to obtain an effect of suppressing the crack of the spray coating film to a certain degree of temperature. However, depending on the applications of the laminate, the base material may be heated to higher temperatures. Therefore, a technique capable of further increasing the temperature at which the crack begins to occur on the spray coating film when heating the base material is desired.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing a laminate in which a spray coating film made of a material different from a base material is formed on the base material, and a laminate in which a temperature at which the crack starts to occur on the spray coating film when heating the base material is increased to be higher than before.

Solution to Problem

To solve the above-described problem and achieve the object, a method of manufacturing a laminate according to the present invention, in which a spray coating film made of a material different from a base material is laminated on the base material, includes: a base material heating step of heating the base material; an intermediate layer forming step of forming, on a surface of the heated base material, an intermediate layer made of a material different from the base material and the spray coating film; and a spray coating film forming step of forming the spray coating film on a surface of the intermediate layer.

The above-described method of manufacturing a laminate is characterized in that compressive stress is accumulated in the intermediate layer at the time of start of the spray coating film forming step.

The above-described method of manufacturing a laminate is characterized by further including a base material lowering step of lowering a temperature of the base material until stress in the intermediate layer becomes compressive stress, after the intermediate layer forming step.

The above-described method of manufacturing a laminate is characterized in that, in the base material heating step, the base material is heated in a range from ⅕ or higher of a melting point of the base material to the melting point or lower of the base material.

The above-described method of manufacturing a laminate is characterized in that, in the intermediate layer forming step, the intermediate layer is formed so that porosity of the intermediate layer is 3% or more.

The above-described method of manufacturing a laminate is characterized in that, in the intermediate layer forming step, the intermediate layer is formed so that a thickness of the intermediate layer is in a range from 100 μm or more to 800 μm or less.

The above-described method of manufacturing a laminate is characterized in that, in the intermediate layer forming step, powders of material of the intermediate layer and a gas are accelerated toward the surface of the heated base material, and the powders are sprayed and deposited on the surface of the base material, while being kept in a solid phase state.

The above-described method of manufacturing a laminate is characterized in that, in the intermediate layer forming step, the material of the intermediate layer is thermally sprayed onto the surface of the heated base material.

A laminate according to the present invention includes: a base material; an intermediate layer made of a material different from the base material; and a spray coating film which is made of a material different from the base material and the intermediate layer, and is formed on a surface of the intermediate layer, wherein compressive stress is accumulated in the intermediate layer at room temperature.

The above-described laminate is characterized in that porosity of the intermediate layer is 3% or more.

The above-described laminate is characterized in that a thickness of the intermediate layer is in a range from 100 μm or more to 800 μm or less.

The above-described laminate is characterized in that the base material is made of a metal or an alloy, and the spray coating film is made of ceramic or cermet.

The above-described laminate is characterized in that the intermediate layer is formed by accelerating powders of the material different from the base material and a gas toward a surface of the base material, and by spraying and depositing the powders onto the surface of the base material, while being kept in a solid phase state.

The above-described laminate is characterized in that the intermediate layer is formed by thermally spraying a material different from the base material onto the surface of the base material.

Advantageous Effects of Invention

According to the present invention, since an intermediate layer is formed on the base material while heating the base material and a spray coating film is formed on the surface of the intermediate layer, it is possible to increase a temperature at which the crack starts to occur on the spray coating film when heating the base material to be higher than before.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited by the following embodiments. Also, each drawing referred to in the following description merely schematically illustrates the shape, the size and the positional relationship to the extent capable of understanding the contents of the present invention. That is, the present invention is not limited only to the shape, the size, and the positional relationship exemplified in each drawing.

Embodiment

FIG. 1is a flowchart illustrating a method of manufacturing a laminate according to an embodiment of the present invention.FIG. 2is a schematic diagram illustrating the method of manufacturing the laminate according to the present embodiment and the stress state in the laminate.

First, in step S1, a base material10of a laminate is provided and heated. The material of the base material10is not particularly limited as long as the material is a metal or an alloy. For example, depending on the use of the laminate, it is possible to use copper, copper alloys, zinc, zinc alloys, aluminum, aluminum alloys, magnesium, magnesium alloys, nickel, nickel alloys, iron, iron alloys, iron-nickel alloys, stainless steel, titanium, titanium alloys, chromium, chromium alloys, niobium, niobium alloys, molybdenum, molybdenum alloys, silver, silver alloys, tin, tin alloys, tantalum, tantalum alloys or the like.

A heating method of the base material10is not particularly limited, and the base material10may be simply placed on a hot plate that is set to a predetermined temperature. Further, the temperature (set temperature) for heating the base material10is preferably set in a range from ⅕ or higher of the melting point of the base material10to the melting point or lower, and the base material10is preferably heated to a temperature that is assumed when using the completed laminate. The temperature T of the base material10at this time is set as T=T0.

In a subsequent step S2, as illustrated inFIG. 2(a), while heating the base material10, an intermediate layer11is formed on the surface of the base material10. In this embodiment, the intermediate layer11is formed by a cold spraying method.

As the material of the intermediate layer11, a metal or an alloy having a thermal expansion coefficient between the base material10and a spray coating film formed in a subsequent step S4is used. For example, the material of the intermediate layer11may be suitably selected according to the combinations of the materials of the base material10and the spray coating film, from copper, copper alloys, zinc, zinc alloys, aluminum, aluminum alloys, magnesium, magnesium alloys, nickel, nickel alloys, nickel-aluminum alloys, iron, iron alloys, iron-nickel alloys, stainless steel, titanium, titanium alloys, chromium, chromium alloys, niobium, niobium alloys, molybdenum, molybdenum alloys, silver, silver alloys, tin, tin alloys, tantalum, tantalum alloys or the like.

The cold spraying method is a film forming method of injecting powders of metal or alloy in a state of a melting point or a softening point or lower, and an inert gas from a nozzle, and causing the powders and the inert gas to collide with the base material in a solid phase state, thereby forming a film on the surface of the base material. In the cold spraying method, as compared to the thermal spraying method of spraying the powders of the material to the base material by melting the powders, the film formation is performed at low temperatures. Therefore, according to the cold spraying method, it is possible to alleviate the effects of thermal stress, and it is possible to obtain a metal film in which oxidation is also suppressed without any phase transformation.

FIG. 3is a schematic diagram illustrating a configuration example of a film forming device according to the cold spraying method, a so-called cold spraying device. A cold spraying device100illustrated inFIG. 3includes a gas heater101that heats the compressed gas, a powder feeder102that houses the powders of the material of the film and supplies the powders to a spray gun103, a gas nozzle104that injects the powders of the material supplied to the spray gun103and the heated compressed gas toward the base material10, and valves105and106that regulate an amount of supply of compressed gas to the gas heater101and the powder feeder102.

As the compressed gas, an inert gas such as helium, nitrogen and air is used. The compressed gas supplied to the gas heater101is supplied to the spray gun103, after being heated to a temperature of a range that is lower than the melting point of the powders of the material. The heating temperature of the compressed gas is preferably in a range from 300 to 900° C.

Meanwhile, the compressed gas supplied to the powder feeder102supplies the powders of material of the powder feeder102to the spray gun103to a predetermined discharge rate.

The heated compressed gas is injected at an approximately supersonic flow of 340 m/s or more by passing through the gas nozzle104having a divergent shape. The gas pressure of the compressed gas at this time is preferably in a range approximately from 1 to 5 MPa. The reason is that it is possible to improve the adhesion strength of the film, that is, the intermediate layer11to the base material10, by adjusting the pressure of the compressed gas to such an extent. More preferably, the compressed gas may be treated with a pressure in a range approximately from 2 to 4 MPa.

In such a cold spraying device100, the base material10is disposed on a downstream side in an injection direction of the spray gun103, the powders of the material of the intermediate layer11are charged to the powder feeder102, and the supply of the compressed gas to the gas heater101and the powder feeder102is started. Thus, the powders supplied to the spray gun103are charged into the supersonic flow of the compressed gas to be accelerated, and are injected from the spray gun103. The powders collide with the base material10at high speed while being kept in the solid phase state and are deposited to form the intermediate layer11.

In such a cold spraying method, when the powders of material collide with an under layer, that is, the base material10and the film formed earlier, a plastic deformation occurs to obtain an anchor effect. At the same time, each oxide film is destroyed and the metallic bond caused by newly formed surfaces occurs. Accordingly, it is possible to form the intermediate layer11having high adhesion strength with the base material10. Therefore, it is possible to determine whether the intermediate layer11is formed by the cold spraying method, by observing the presence or absence of the anchor layer at the interface between the base material10and the intermediate layer11, a laminated state of the powders and the like.

Here, while forming the intermediate layer11, in some cases, the temperature of the base material10may change from the set temperature in the step S1, but it does not cause a problem. In short, heating may be continued at the set temperature, and there is no need to strictly maintain the base material10itself at a constant temperature.

It is preferable that the thickness of the intermediate layer11be approximately in a range from 100 μm or more to 800 μm or less. More preferably, the thickness may be approximately in a range from 200 μm or more to 500 μm or less. Further, the density among the film qualities of the intermediate layer11may be preferably relatively coarse, and specifically, the porosity may be preferably 3% or more, and more preferably may be 5% or more. The film thickness and the porosity of the intermediate layer11can be controlled, by appropriately adjusting the film formation conditions such as the relative scanning speed between the spray gun103and the base material10, the pressure of the compressed gas, and the flow rate of the powders of material.

Further, as long as it is possible to form a film by causing the powders of material to collide with the base material10, while being kept in the solid phase state, the cold spraying device is not limited to the configuration illustrated inFIG. 3. Further, in the step S2, as long as it is possible to form a film of metal or alloy which has the film thickness and the porosity of the aforementioned ranges and has high adhesion strength to the base material10, the intermediate layer11may be formed by a method other than the cold spraying method. Hereinafter, the film of metal or alloy will be collectively referred to as a metal film. Specifically, a metal film formed by the thermal spraying method may also be used the intermediate layer11.

In a subsequent step S3, as illustrated inFIG. 2(b), the base material10and the intermediate layer11are cooled to a temperature T1(T1<T0, for example, a room temperature) that is lower than the temperature at the time of formation of the intermediate layer11. Further, the room temperature is in the vicinity of 25° C. At this time, cooling may be positively performed, for example, by blowing the air toward the base material10formed with the intermediate layer11, and the base material10may be only left in the room temperature. When cooling the base material10and the intermediate layer11, the compressive stress, that is, a negative stress remains on the intermediate layer11.

In the subsequent step S4, as illustrated inFIG. 2(c), a spray coating film12is formed on the surface of the intermediate layer11. As the material of the spray coating film12, a ceramic-based material, and a mixed material of metal and ceramics are used.

As the ceramic material, for example, it is possible to use oxide ceramics such as alumina, magnesia, zirconia, yttria, yttria-stabilized zirconia, steatite, forsterite, mullite, titania, silica and sialon, non-oxide ceramics such as aluminum nitride, silicon nitride, silicon carbide, titanium nitride, titanium carbide, titanium carbonitride, titanium aluminum nitride, titanium chromium nitride, chromium nitride, zirconium nitride, chromium carbide and tungsten carbide, or a BCN-based super hard material such as boron carbide and boron nitride.

As the mixed material of metal and ceramics, it is possible to use ceramics such as oxides, nitrides, carbides and borides, specifically, mixed materials which contain the aforementioned ceramic material as the main component, and contain a metal or an alloy as a binder phase or tie, a so-called cermet. For example, a mixed material in which the metal powders such as cobalt or nickel are dispersed in the powders of tungsten carbide as the tie may be used. Alternatively, materials such as mixed composition of yttria stabilized zirconia (YSZ) and nickel (Ni)-chromium (Cr) alloy may be used.

While the spray coating film12is formed, since the material melted by the spray coating flame is sprayed into the intermediate layer11, the base material10and the intermediate layer11enter a heated state, for example, approximately in a range from 70 to 80° C. Therefore, compressive stress remaining on the intermediate layer11becomes slightly smaller than the state illustrated inFIG. 2(b). The temperature T of the base material10at this time is set as T=T2(T1≤T2<T0).

The surface of the intermediate layer11formed by the cold spraying method forms a complex convex shape toward the outside. Therefore, the material of the melted spray coating film12enters a narrow recessed portion between the protrusions of the surface of the intermediate layer11to improve the anchor effect of the spray coating film12. Thus, the intermediate layer11and the spray coating film12are firmly bonded to each other to obtain a high adhesion strength. Therefore, even by observing the interface between the intermediate layer11and the spray coating film12, it is possible to determine whether the intermediate layer11is formed by the cold spraying method.

Thus, a laminate13illustrated inFIG. 2(c)is completed. Here, after the formation of the spray coating film12, when the temperature of the laminate13is lowered, the compressive stress is generated in the intermediate layer11. However, as described above, since the intermediate layer11and the spray coating film12are firmly bonded to each other, the high adhesion strength is maintained.

Next, the stress state in the laminate13illustrated inFIG. 2will be described by comparison withFIGS. 4 to 6.FIGS. 4 to 6are schematic diagrams illustrating a stress state in the laminate manufactured by a conventional method. The arrows illustrated in each drawing illustrate the internal stresses in the layer on which the arrows are indicated. Specifically, the outward arrows indicate the tensile stress, and the inward arrows indicate the compressive stress.

As illustrated inFIG. 4(a), the case of manufacturing a laminate22by directly forming a spray coating film21on a base material20at room temperature condition will be described. When forming the spray coating film21, by spraying the molten material onto the base material20, the base material20is slightly heated. The temperature T of the base material20at this time is set as T=T2.

When heating the base material20side of the laminate22, as illustrated inFIG. 4(b), due to the influence of thermal expansion of the base material20, a tensile stress is generated on the spray coating film21. When the temperature T of the base material20is higher than the temperature T2at the time of formation of the spray coating film21, the crack occurs in the spray coating film21.

The case of manufacturing a laminate33by forming an intermediate layer31on a base material30of the room temperature condition as illustrated inFIG. 5(a)and by forming a spray coating film32on the intermediate layer31as illustrated inFIG. 5(b)will be considered. The intermediate layer31may be formed by the cold spraying method as in the above embodiment, and may be formed by the thermal spraying method.

As illustrated inFIG. 5(c), when heating the base material30side of the laminate33, due to the influence of thermal expansion of the base material30, a tensile stress is generated on the intermediate layer31and the spray coating film32. Of these, the tensile stress generated in the spray coating film32is alleviated by the intermediate layer31interposed between the spray coating film32and the base material30. Therefore, even when the temperature T of the base material30is made higher than the temperature (T=T2) at the time of formation of the spray coating film32(T>T2), the crack of the spray coating film32can be prevented to some extent. However, as illustrated inFIG. 5(d), when the temperature T of the base material30is further increased (T>T3>T2), the effect of alleviating the tensile stress caused by the intermediate layer31reaches limit, and the crack occurs in the spray coating film32.

As illustrated inFIG. 6(a), the case of forming a spray coating film41while heating a base material40to a temperature T4at the time of use of a laminate42will be considered. In this case, as illustrated inFIG. 6(b), when cooling the laminate42, for example, to the vicinity of the room temperature after the formation of the spray coating film41, a state in which compressive stress remains on the spray coating film41occurs.

As illustrated inFIG. 6(c), when heating the base material40side of the laminate42, due to the influence of thermal expansion of the base material40, the compressive stress remaining on the spray coating film41is gradually reduced. This effect continues until the temperature T of the base material40reaches a temperature T4at the time of formation of the spray coating film41. Therefore, until the temperature T of the base material40reaches the temperature T4at the time of formation of the spray coating film41, it is possible to heat the base material40, without causing the crack on the spray coating film41.

However, as illustrated inFIG. 6(d), when the temperature T of the base material40exceeds the temperature T4, the stress of the spray coating film41changes to the tensile stress from the compressive stress. Therefore, when the base material40is continuously heated, the crack occurs on the spray coating film41.

Further, as illustrated inFIG. 6(c), when the laminate42is used at the temperature T4or lower, there is no problem even when the spray coating film41is directly formed on the base material40, without providing the intermediate layer. Therefore, in order to enhance the heat resistance of the spray coating film41at the time of the use of the laminate42, it is conceivable to raise the base material temperature T4at the time of formation of the spray coating film41. However, when the spray coating film41is formed of ceramics, if the base material temperature T4increases, at the time of returning the temperature of the laminate42to the approximately room temperature after the formation of the spray coating film41(seeFIG. 6(b)), there is concern that the spray coating film41peels off from the base material40due to the influence of heat contraction of the base material40. Although the base material temperature T4at which peeling occurs when returning to the room temperature depends on the combinations of the material of the base material40and the material of the spray coating film41, for example, when forming an alumina spray coating film on an aluminum base material, if the base material temperature T4is set to approximately 200° C., peeling occurs. Therefore, in this case, it is not possible to greatly increase the base material temperature T4.

In contrast with the laminates22,33and42manufactured by the conventional methods, in the laminate13according to this embodiment, it is possible to heat the base material10to a higher temperature, without causing crack in the spray coating film12. That is, as described above, in the vicinity of the room temperature, compressive stress remains in the intermediate layer11(seeFIG. 2(c)). Therefore, as illustrated in2(d), when heating the base material10side of the laminate13, the intermediate layer11also gradually expands due to the influence of thermal expansion of the base material10, and the compressive stress remaining in the intermediate layer11is gradually reduced. As illustrated inFIG. 2(e), this effect continues until the temperature of the base material10reaches the base material temperature T0at the time of formation of the intermediate layer11. At this time, although the tensile stress begins to occur in the spray coating film12due to the influences of the thermal expansion and the rigidity of the intermediate layer11, an increase in the tensile stress is very gentle as compared to the spray coating films21,32and41illustrated inFIGS. 4 to 6.

Thus, in the laminate13according to the present embodiment, it is possible to heat the base material10to the base material temperature T0at the time of formation of the intermediate layer11or a temperature exceeding that temperature, without causing crack on the spray coating film12.

As the conditions of the intermediate layer11usable as a substrate of the spray coating film12, there is a condition in which the intermediate layer is not peeled off from the base material when cooling the temperature of the base material to the approximately room temperature after formation of the intermediate layer, even in the case of forming the intermediate layer by heating the base material to the use temperature (seeFIG. 6(d)) at which peeling is caused when directly forming the spray coating film on the base material. As such an intermediate layer, a metal film formed by the cold spraying method or the thermal spraying method described above is suitably used. Among them, the metal film obtained by the thermal spraying method can be used as the intermediate layer, when the adhesion strength of the metal film to the base material is higher than the adhesion strength of the spray coating film of ceramic serving as an upper layer.

Further, the effect of alleviating the tensile stress in the spray coating film12, in other words, the effect of suppressing the crack of the spray coating film12when heating the laminate13becomes larger, as the film quality of the intermediate layer11is coarse, and as the film thickness of the intermediate layer11is thick. However, when the intermediate layer11is too thick, since the thickness of the laminate13itself increases, the film thickness of the intermediate layer11is preferably approximately in a range from 100 μm to 800 μm, and more preferably approximately in a range from 200 μm to 500 μm.

EXAMPLES

Hereinafter, an example according to the present invention will be described with reference toFIG. 7.FIG. 7is a table illustrating the preparation conditions and evaluations of the samples in examples and reference examples according to the present invention.

(1) Preparation of Sample

As examples and reference examples according to the present invention, three kinds of samples illustrated inFIG. 7were prepared. The materials of each layer constituting each sample were as follows.

In the first and second examples and the first reference example, the thickness of the intermediate layer, the heating temperature of the base material at the time of formation of the intermediate layer, and the density among the film qualities of the intermediate layer were changed. Among the film qualities illustrated inFIG. 7, “coarseness” indicates that the porosity of the intermediate layer is 3% or more, and “denseness” indicates that the porosity of the intermediate layer is less than 3%. Further, the spray coating film was subjected to cutting until the thickness becomes 135 μm after the film formation.

(2) Evaluation of Sample

Each sample was placed on a hot plate, and heating was performed from the base material side. After heating the sample to each set temperature (300° C., 350° C., 400° C. and 450° C.), the sample was naturally cooled to the room temperature, and the presence or absence of crack in the spray coating film was checked by the color check. The symbol x in the column of the spray coating heat resistant temperature illustrated inFIG. 7indicates that the crack occurs in the spray coating film at that temperature, and the symbol ◯ indicates that the crack does not occur in the spray coating film at that temperature.

First Example

In the first example, while heating the base material to 400° C., an intermediate layer having a film thickness of approximately 130 μm and a dense film quality was formed. In this case, even if the base material of the laminate was heated to 350° C., the crack did not occur in the spray coating film.

Second Example

In the second example, while heating the base material to 400° C., an intermediate layer having a film thickness of approximately 300 μm and a coarse film quality was formed. In this case, even if the base material of the laminate was heated to 400° C., crack did not occur in the spray coating film.

First Reference Example

In the first reference example, an intermediate layer having a film thickness of approximately 130 μm and a dense film quality was formed, without heating the base material, that is, while being kept at room temperature. In this case, when heating the base material of the laminate to 350° C., crack occurred in the spray coating film.

From these experimental results, it is possible to improve the heat resistance temperature of the spray coating film by forming the intermediate layer, while heating the base material. Specifically, when comparing the first example to the first reference example, it was confirmed that the heat resistance temperature of the spray coating film was improved in the case of increasing the base material temperature at the time of formation of the intermediate layer.

Further, when comparing the first example to the second example, it was possible to improve the heat resistance temperature of the spray coating film when the film thickness of the intermediate layer is increased. This is considered to be due to the fact that, by increasing the thickness of the intermediate layer, the influence of the thermal expansion of the base material on the spray coating film becomes gentler when heating the sample. Furthermore, when the film quality of the intermediate layer made coarse, it was possible to further improve the heat resistance temperature of the spray coating film. This is considered to be due to the fact that, by the coarse intermediate layer, the influence of the thermal expansion of the base material on the spray coating film also becomes gentler.

REFERENCE SIGNS LIST