JPH06104887B2 - Ceramic spraying material and spraying method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic spray material used for ceramic spraying using a plasma gun and a method for spraying using the ceramic spray material.

(Prior art and its problems) Ceramic coating by thermal spraying on metal materials is an effective method for improving the heat resistance, heat insulation and corrosion resistance at high temperatures, and in recent years, it has been related to effective use of energy. It is applied to various device members described above. However, as the application is expanded, the operating conditions become severer, and therefore it is necessary to further improve the denseness and bondability of the coating. In particular, it is necessary to enhance the adhesion of the ceramic coating itself in terms of simultaneously satisfying the denseness and the bondability and connecting the coating effect.

Therefore, conventionally, regarding the molten state of the sprayed material particles and the flight state as droplets, it has been possible to improve the equipment and method of forming conditions (for example, heat quantity and momentum) of spraying flame and construction conditions (for example, spraying distance). It has been advanced.

Further, the droplets flying during thermal spraying form a film by laminating on the base material (metal material), but each droplet is a kind of interlocking state and the base material or laminated film (from one droplet It is said that the interlock state is improved, and it is important to improve this interlocking state. That is, the interlocked state in thermal spraying is not merely the background of the adhesion force which is an evaluation guideline, but the morphology of the structure that forms the basis of the denseness and bondability of the laminated film formed by individual droplets.

In order to enhance the interlock effect, the following methods have been conventionally used for ceramic spraying.

(Conventional Example 1) Roughening of the substrate surface by shot blasting and / or cleaning with an organic solvent (Fig. 2).

However, in such a method, it is easy to peel due to the thermophysical property value (generation of thermal strain) between the ceramic layer 1 and the base material 2.

(Conventional Example 2) A method of pre-spraying (undercoating) a Ni-based or Co-based alloy in advance for the purpose of relaxing the thermal strain of the above-mentioned Conventional Example 1 (third embodiment)
Figure).

However, in this method, the ceramic layer 1 is easily peeled off when a heat cycle is applied. In the figure, 3 is an undercoat layer.

(Conventional Example 3) A method of interposing a cermet layer 4 in which the alloy and the ceramic are mixed in order to reduce the difference in thermal expansion in the coating in the above-mentioned Conventional Example 2, or a metal / ceramic ratio in the laminating step in the cermet layer 4. A method of subdividing and stacking (FIG. 4).

However, this film only obtains a good adhesion with the base material 2 in the laminated area in which the metal is interposed, and the peeling proceeds in the ceramic layer 1.

(Conventional Example 4) A method of densifying a ceramic surface by laser irradiation after forming a ceramic layer by thermal spraying (JP-A-59-96273, No. 5)
Figure).

However, in this method, since a laser irradiation machine is installed and secondary processing is performed, the versatility is limited in terms of the shape of a substrate that can be processed and economical efficiency. In particular, since the ceramic layer 1 forms two layers, the dense layer 5 and the untreated layer 6, the ceramic layer 1
It is not possible to improve the adhesion of itself.

(Prior art example 5) A method of obtaining, for example, ZrO ₂ —NiO—Ni-based composite base particles by nickel-plating the surface of a thermal spray material (powder particles) and thermal spraying the same (The 33rd Academic Lecture of the Japan Thermal Spray Society) Tournament summary, Figure 6).

However, this method does not produce intermediate products (eg MgNi
O ₂ ) is secondarily formed, and the secondary product strengthens the coating as a binding layer, but it is inferior in terms of heat resistance which is the original characteristic of the ceramic coating.

As described above, in the conventional method, a certain improvement effect is recognized and each method is used individually, but it does not necessarily meet the severe operating conditions.

Therefore, the present inventors have studied in detail the structure morphology of various ceramic sprayed coatings, and as a result, have found that the desired object can be achieved by spraying a mixture of metal powder and ceramic powder ( (Fig. 1).

Note that what is called a conventional cermet thermal spraying material is, for example, a ni-based, Co-based alloy powder and TiN, a mixed powder of carbonitride-based ceramic powder such as WC, and an oxide-based ceramic for the purpose of the present invention. Is different.

Further, JP-A-56-59679 previously disclosed by the present inventors,
Regarding the material, it is a repair material of the same system as that of a kiln, and unlike the present invention, the present invention is a thermal spray material intended for surface coating with a film thickness of about 1 mm.

Further, in order to improve the denseness of the initial coating before use, heat treatment of the substrate containing the coating is effective. The heat treatment method of the thermal spray coating is generally called fusing, and is a method mainly applied to the thermal spray coating of the self-fluxing alloy. This conventional method is a method of melting the coating surface again with a gas burner after spraying to promote sealing of pores and diffusion of alloy components to the base material, and usually heats and cools at 800 to 900 ° C. However, it is impossible to apply such a method to the ceramic coating according to the present invention for the following reason.

Since the once cooled film is rapidly heated and cooled, the ceramic layer is peeled off.

The residual metal phase in the coating causes rapid oxidation and destroys the coating structure.

Therefore, in the investigation of the method of the present invention, it was found that it is effective to use the above-mentioned materials and simultaneously heat the base material and the coating in a series of thermal spraying steps including pretreatment.

(Means for Solving Problems) The first aspect of the present invention is to use Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ , TiO ₂ or NiO-based oxide alone in a ceramic powder as a cation in the oxide. The same metal element powder as the above, the ceramic powder 100vol%
The ceramic sprayed material is characterized in that 1 to 10 vol% is added thereto.

That is, the thermal spray material of the present invention is formed by adding and mixing powders (hereinafter referred to as “M”) of the same metal element as the cations in the oxide to these ceramics and individual powders (hereinafter referred to as “MO _x ”). Is done. The reason why the metal powder of the same element is mixed with these ceramic powders is as follows.

The partial oxidative combustion of the metal powder promotes melting of the ceramic particles.

Minute ceramic droplets of the same composition are layered from the metal that has been oxidized and burned to densify the ceramic film,
Increases connectivity.

In some cases, the unoxidized or incompletely oxidized metal particles and the ceramic particles easily wet each other in the form of liquid droplets, and form mutually favorable interlocking layers.

The metal phase remaining in the ceramic coating is relatively plastic, and in the solidification process of thermal spray lamination, residual pressure is applied to the adjacent ceramic phase to enhance the bonding strength.

During the use process or heat treatment, the melting and oxidation of the residual metal phase in the film progresses, the porosity of the film decreases and the bond strength increases, and the expansion of microcracks in the ceramic in the film is prevented and the bond strength is maintained.

The droplets of unoxidized or incompletely oxidized metal particles easily wet the base material or the undercoat surface, which is a metal material, and promote the adhesion of the ceramic layer. Particularly, by strictly adjusting the blending amount of the thermal spray powder as follows, a good bonding state of these coatings can be obtained, and the improvement of the adhesiveness can be more effectively achieved.

The amount of M added is 1 to 10 vol%. This is the external coating ratio to MO _x 100 vol%, and the value obtained by converting the bulk specific gravity of MO _x powder (approximately 1.0) into the bulk specific gravity of each M powder is applied. This is because most of the composition of less than 1 vol% burns out, and a film containing the required metal phase cannot be obtained. Also 10vo
This is because the heat resistance of the entire coating is remarkably reduced when the content is 1% or more. Since the main condition of the thermal spray flame is the thermal spraying of ceramics, an excessive amount of heat causes the M powder to be in an overheated state, causing a large amount of bubbles.

On the other hand, the compositional purity of each of the M and MO _x powders to be subjected to thermal spraying must be at least the above in principle.

In the case of M powder, the impure components are C, Fe, Si, Mn, S, etc.,
Most of them are mixed during the manufacturing process, and it is easy to form an oxide phase after the thermal spraying separately from the required ceramic layer. Further, even if these are solid solution components, some of them cause an endothermic reaction or a gasification reaction in the oxidation process during thermal spraying, which causes defects in the coating film.

The same applies to the case of MO _x powder, but there is no problem as long as it forms a single mineralogy phase (mineral phase) as a solid solution. For example, the Y ₂ O ₃ component and CaO component in the ZrO ₂ powder, or the TiO ₂ component in the Al ₂ O ₃ powder do not form separate oxide phases, but a positive component in each main component phase within a certain composition range. Since it forms a solid solution as an ion, it enhances the mineral phase stability. Of course, even if Zr or Al is added in the ceramic phase after thermal spraying and the solid solubility decreases, it has little effect on various physical properties,
Rather, as a film, the effect of interlocking the metal phase and the ceramic phase in the film largely appears.

The particle size of the thermal spray powder is preferably within the following range.

Usually, the particle size of the oxide ceramic powder is in the range of 15 to 100 μm, while the particle size of the metal powder is 5 to 50 μm.

This is because if it is less than 5 μm, it is easy to burn and scatter during thermal spraying, and a phase required for film formation is not formed. Further, when it is 50 μm or more, it is easy to form a coarse independent metal phase to form point defects,
This is because low melting deterioration is caused. Particularly, in order to evenly oxidize the metal phase and disperse the unoxidized phase, it is desirable that the MO _x powder and the M powder are in the ranges of 40 to 80 μm and 10 to 20 μm, respectively.

As described above, in the present invention, by forming the pseudo-cermet coating, so to speak, it is possible to achieve thermal spraying with high adhesion while maintaining heat resistance as a ceramic coating. In addition, 10 in FIG. 1 shows a pseudo cermet layer.

Next, the second aspect of the present invention is to perform Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ , TiO ₂ or N in a series of ceramic spraying processes including pretreatment.
To the ceramic powder of the iO-based oxide alone, the same metal element powder as the cations in the oxide was added to the ceramic powder 100v.
550 to 200 of base material during or immediately after thermal spraying of ceramic thermal spray material composed by adding 1 to 10 vol% to ol%
The ceramic spraying method is characterized in that the coating surface is once heat-treated at a temperature of less than 1300 ° C while maintaining the temperature at ℃.

In the thermal spraying method of the present invention, the base material and the coating are simultaneously heated in a series of thermal spraying steps. 550 ℃ to 2 for the base material
In the range of 00 ℃, it is kept in a heated state before the thermal spraying. Then, after forming the film in this state, the temperature of the outermost surface of the film is further raised in the range of less than 1300 ° C. to be cooled, and after the material temperature has dropped to 200 ° C., the whole is allowed to cool.

The preheating temperature of the base material means the average temperature of each part, but 550
If it exceeds ℃, thermal deterioration may be accelerated. Also, 20
If it is less than 0 ° C, peeling easily occurs between the substrate and the film.

The temperature of the surface of the film is below the melting point of M powder and is in the softening region, which suppresses rapid oxidation of the metal phase and at the same time suppresses the temperature difference between the base material and the film surface to less than 1300 ° C. effective. Considering the oxidation reaction of M powder, many
A processing temperature of 700-1000 ° C is sufficient for the purpose.

It is desirable to adjust the temperature rising / falling rate during heat treatment to 1 to 5 ° C / min. This is because if it is less than 1 ° C / min, the work efficiency is hindered. In particular, it is necessary to set the rate to 5 ° C./min or less in order to reduce the oxidation rate at the time of temperature rise or the thermal strain at the time of temperature decrease. Of course, no adjustment is necessary in the preheating stage of the base material and the stage of cooling to 200 ° C. or lower where it is not necessary to pay attention to the above points.
Further, as the heat treatment of the coating, it is a matter of course to start the treatment immediately after thermal spraying in the sense of not giving unnecessary thermal shock.

As a heat source for such heat treatment, an atmosphere in an electric furnace, an infrared heater, a thermal spray frame, or resistance heating of a substrate (Japanese Patent Laid-Open No. 216756/58) is effective.

These heat sources are used separately for heating the substrate and heating the coating surface. In order to secure the work efficiency of heat treatment, it can be said that it is most advantageous to preheat the substrate in the electric furnace, perform the thermal spraying process, and heat the coating surface with the thermal spray gun frame. In the present invention, since the metal powder M is 10 vol% or less, there is no problem such as explosion due to the material which is not melted and scattered.

When the pseudo cermet film as described above is heat-treated, the residual metal powder M in the film is gradually oxidized during the temperature rising / falling process of the heat treatment, and minute MO _x phases are crystallized, so that the pores in the film are reduced.
A densified ceramic film can be formed and adhesion does not decrease.

Of course, even in the case of a film that is not subjected to such a series of heat treatments, the same change occurs at the surface portion depending on the operating temperature, so there is no problem in terms of heat resistance as a ceramic film and strength retention due to densification. .

(Operation) In the present invention, Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ , TiO ₂ or NiO-based oxide alone is added to a ceramic powder, and the same metal element powder as the cation in the oxide is added to the ceramic powder. In a series of ceramic spraying processes including a ceramic spraying material containing 1 to 10 vol% of powder to 100 vol% of powder and pretreatment, Al ₂ O
_3, the oxide single ceramic powder _{ZrO 2, Cr 2 O 3,} TiO 2 or NiO system, the same metallic element powder and a cation in the oxide, 1～10Vol% with respect to the ceramic powder 100 vol%
A good bonding state of the coating because the coating surface is once heat-treated at less than 1300 ° C while holding the base material at 550 to 200 ° C during and / or immediately after the thermal spraying of the ceramic sprayed material added. Is obtained and the adhesion becomes good.

(Examples) Examples of ceramic sprayed coatings according to the present invention will be shown below.

The spraying machine used was a plasma jet gun with a powder external feeding function, and a combination of Ar, N ₂ and H ₂ gases was used as the working gas. The plasma was operated with an output current of 600 A to 900 A and an output of 40 to 50 kw. However, the individual conditions were all constant within the ceramic material system.

In addition to the operating conditions, the powder (spray material) feed rate, the spray gun scanning speed, and the spray distance were also constant within the same material.
The base material is SS-41 or SUS-304, and the shape is 50 x 150 x 3.2.
(Mm) constant shape. As a pretreatment of the base material, it was blasted with alumina grit and washed with an acetone solution. Further, NiCrAlY alloy powder was sprayed under the space between the ceramic layers (top coat) coating, and the material of the method of the present invention and the conventional material were sprayed on the undercoat of 100 to 150 μm.

As a heat treatment method, the base material is heated by an electric furnace or a resistance heating method for the base material, and in order to maintain the temperature of the opposite surface of the base material during thermal spraying or heating of the coating surface, 40 to 60 l / min Ar gas is used. Gas cooled. An infrared heater was used to heat the coating surface. To adjust the temperature rise and fall, the heater output was adjusted by measurement in a non-contact type temperature system.

In addition, the adhesion of the obtained film is quantified by the torque when the bolt (SS-41) with a cross-sectional area of 2 cm ² is fixed with epoxy resin and the torsional strength is measured with a torque wrench, and the film is obtained by the conventional method. Adhesion index of 100 was set as 100 and shown as a ratio.

Incidentally, the coating by the conventional method was peeled off in the ceramic coating by 90% or more during the measurement, and by the coating by the method of the present invention, 85% or more was peeled off at the interface between the ceramic layer and the undercoat during the measurement.

The porosity was shown by the cumulative porosity obtained by a mercury porosimeter using a release film obtained by the above measurement by incinerating the resin at 300 ° C. The porosity of the coating by the conventional method is set to 100 and shown as a ratio to this. However, as is clear from the sample collection method, the actual porosity of the conventional method can be said to be more uniformly porous than the values obtained by the porosimeter.

The coating properties according to the present invention are shown in Tables 1 to 3 in comparison with the conventional example.
Shown in the table. As a result, it can be easily inferred that the improvement effect is remarkable in terms of adhesion and denseness, and that the bond strength in the film is also improved.

[Part 1 (Table 1)] ZrO ₂ powder (purity: 99%) prepared by adjusting metal Zr powder (purity: 98%) to a particle size of 5 to 40 μm at a blending ratio of _{2 to} 10 vol%.
Is mixed uniformly into a thermal spray material, and SUS-304 is formed by Ar-H ₂ plasma.
The base material (after the surface treatment) was sprayed and coated with a thickness of 500 μm. As a result, as shown in Table 1 below, about 20% of the pores were reduced, and the adhesion was improved about twice.

[Part 2 (Table 2)] Metal Al powder (purity: 97%) adjusted to a particle size of 30 to 50 μm was mixed uniformly with Al ₂ O ₃ powder (usually white alumina) by changing the compounding amount. As a thermal spraying material and SS- with N ₂ -H ₂ plasma
41 base material (after the surface treatment) was sprayed and coated with a thickness of 750 μm.

As a result, as shown in Table 2 below, a maximum amount of 25% reduction in pores was recognized, and the adhesion was improved about 2-3 times. Furthermore, as comparative examples, 2.4% TiO ₂ -containing alumina (usually gray alumina) and TiO ₂ content 13% TiO ₂ -Al ₂ O ₃ (alumina titanate)
With respect to the alumina-based powder containing Al, the film formed by adding 5 vol% of Al powder densified when the amount of TiO ₂ was large, but the adhesion was not necessarily improved.

In addition, the adhesion strength of the coated sample partially heat-treated was significantly improved.

[Part 3 (Table 3)] Purity of 91.3% or more of Cr powder, Ti powder, and Ni powder adjusted to 5 to 50 μm is uniform in Cr ₂ O ₃ powder and TiO ₂ powder at a mixing ratio of ₂ vol%. The mixture was mixed to obtain a thermal spray material, which was sprayed onto an SS-41 base material (undercoating) to form a coating having a thickness of 150 to 200 μm.

As a result, as shown in Table 3 below, the porosity was reduced by about 20%, and about twice the improvement in adhesion was confirmed.

Although the present invention has been variously described above with reference to the embodiments, it will be apparent to those skilled in the art that various modifications and improvements can be made within the scope of the present invention.

(Effects of the Invention) As described above, the present invention provides Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ , and TiO _2.
2 or NiO-based oxide alone ceramic powder, the same metal element powder as the cations in the oxide is added to the ceramic powder 100vol% 1-10vol% ceramic spray material and pretreatment in a series of ceramic spray processes including, the _{Al 2 O 3, ZrO 2,} Cr 2 O 3, the ceramic powder of the oxide single TiO ₂ or NiO system, the same metallic element powder and a cation in the oxide, the Ceramic powder 100vol%
1 to 10 vol% of the ceramic sprayed material is applied to the coating surface during or / and immediately after thermal spraying while maintaining the base material at 550 to 200 ° C while the coating surface is once heat-treated below 1300 ° C. , A good bonded state of the film is obtained, and the adhesion is good. Therefore, according to the present invention, heat resistance is not significantly impaired, good adhesion and long-life coating can be achieved, coating and function can be improved by densification and improvement of bonding strength, and further heat treatment makes it more dense. This is a great invention where the ceramic coating having excellent heat resistance can be achieved.

[Brief description of drawings]

FIG. 1 is a stacking form (cross section) of a ceramic sprayed coating according to the present invention, and FIGS. 2 to 6 are stacking forms ((cross section) views of ceramic sprayed coatings according to Conventional Example 1 to Conventional Example 5. Ceramic layer, 2 as substrate, 3 as undercoat layer,
10 is a pseudo cermet layer.

Claims (2)

[Claims] 1. A ceramic powder consisting of Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ , TiO ₂ or NiO oxide alone, and a metal element powder which is the same as the cation in the oxide are mixed with 100 vol of the ceramic powder. % To 1% to 10% by volume of the ceramic sprayed material. 2. In a series of ceramic thermal spraying processes including pretreatment, Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ , TiO ₂ or NiO-based oxide alone is added to a ceramic powder, and cations in the oxide are added to the ceramic powder. The same metal element powder is added to the ceramic powder in an amount of 1 to 10 vol% with respect to 100 vol% of the ceramic powder, and / or immediately after the thermal spraying of the ceramic spray material, while holding the substrate at 550 to 200 ° C. A ceramic thermal spraying method characterized in that heat treatment is performed once at a temperature of less than 1300 ° C.