JP7298403B2 - Plasma spray equipment - Google Patents

Description

The present invention relates to a plasma spraying apparatus for forming coatings on ceramic substrates.

Conventionally, a plasma spraying apparatus has been widely used for coating a ceramic substrate. By increasing the power supplied to the thermal spraying nozzle, the plasma thermal spraying apparatus can increase the amount of heat generated by the plasma and shorten the coating processing time. However, when processing a film on a rotating ceramic substrate, the area heated by the plasma jet changes as the substrate rotates, so there is a problem that the substrate tends to crack due to the difference in thermal expansion.

As a heat countermeasure, Patent Literature 1 proposes a technique of reducing the temperature in the thermal spray booth by discharging gas containing thermal spray material in the thermal spray booth to the outside. Further, Patent Document 2 discloses a technique in which a cooling nozzle is arranged around the plasma jet, and a cooling gas is sprayed from the cooling nozzle toward the substrate outside the processing area to protect the plate-shaped substrate from high temperatures. ing.

JP 2017-75353 A JP-A-6-122956

However, according to the heat countermeasure of Patent Document 1, since the gas containing the thermal spraying material is discharged outside the thermal spraying booth, the thickness of the coating is reduced, and it takes a long processing time to obtain the required thickness. In addition, according to the heat countermeasure of Patent Document 2, since the cooling gas is blown toward the outside of the coating processing area, part of the thermal spray material is induced by the cooling gas jet flow to flow outside the processing area, and the coating There was a problem that the thickness became insufficient and it was not suitable for high-speed processing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to provide a plasma spraying apparatus capable of suppressing cracking of the ceramic base material and forming a coating having a sufficient thickness in a short time. .

In order to solve the above problems, the plasma spraying apparatus (10) of the present invention comprises a jig (22) that rotatably holds a ceramic substrate (21), and a thermal spray material (19) that rotates while the substrate is rotating. ) toward the substrate to form a coating (23) on the outer surface of the substrate ; A plurality of cooling nozzles (24) which have slit-shaped gas outlets (241) extending in the rotation axis direction of the material and inject cooling gas (26) from the periphery of the plasma jet toward the substrate while the substrate is rotating. ) and Further, the axes (242) of the plurality of cooling nozzles intersect with each other, and the distance from the position where the axes of the plurality of cooling nozzles intersect to the substrate and the distance from the position where the axes of the plurality of cooling nozzles intersect to the thermal spray nozzle , the distance from the position where the axes of the cooling nozzles intersect to the substrate is smaller, and the position where the axes of the cooling nozzles intersect in the axial projection of the substrate is , within the outer diameter of the fixture.

According to the above configuration, the coating is formed by the thermal spray material while the base material is rotating, and at the same time, the coating is cooled by the cooling gas. Therefore, each part of the ceramic substrate can be heated at a uniform temperature, and cracking of the substrate can be suppressed. In addition, since the cooling gas is sprayed from the periphery of the plasma jet toward the substrate, the thermal spray material is gathered on the outer surface of the substrate on the cooling gas jet, and the coating is processed in a short time with a sufficient thickness. is also possible.

In a preferred embodiment of the invention, the cooling nozzles are arranged symmetrically with respect to the thermal spray nozzle axis (141). Axes (242) of the plurality of cooling nozzles intersect each other obliquely at a location closer to the spray nozzle than the substrate. The substrate has an outer surface that includes a cylindrical or conical surface. The thermal spray nozzle is provided so that the relative position with respect to the base material is variable. The cooling nozzle has a slit-shaped gas outlet (241) extending in the rotation axis direction of the substrate.

1 is an elevational view of a plasma spray apparatus showing an embodiment of the present invention; FIG. 2 is a plan view of the plasma spraying apparatus of FIG. 1; FIG. It is (a) a front view, (b) a cross-sectional view which shows an example of a base material. It is (a) a nozzle layout diagram and (b) a dimension table showing test conditions for evaluating cracks in a base material and film thickness. (a) Table showing evaluation results of cracks, (b) Table showing evaluation results of film thickness. It is supplementary explanatory drawing of an evaluation result.

(one embodiment)
An embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, in the plasma spraying apparatus 10 of this embodiment, a frame 12 is installed inside a thermal spraying booth 11, and a thermal spraying nozzle 14 is vertically movable via a bracket 13 on the frame 12. installed. The thermal spray nozzle 14 has a body 142 and a nozzle head 143. The body 142 is provided with a gas inlet 16 for introducing a plasma working gas 15 made of an inert gas such as argon or nitrogen, and a powder thermal spray material 19 such as metal or ceramic. A material inlet 17 is provided for introduction.

The nozzle head 143 internally generates plasma by arc discharge, melts the powder thermal spray material 19 with the heat of the plasma, and injects the plasma jet 20 containing the thermal spray material 19 toward the ceramic substrate 21 . The substrate 21 is, for example, an O ₂ sensor that measures the amount of oxygen in the exhaust gas, and is rotatably held around a vertical axis 213 by a jig 22 . As shown in FIG. 3A, the base 211 of the substrate 21 is held by the jig 22, and the outer surface of the main body 212 becomes a gently conical or cylindrical surface extending along the rotation axis 213 of the substrate 21. As shown in FIG. ing. Then, as shown in FIG. 3B, while the substrate 21 is rotating, the thermal spraying nozzle 14 vertically changes its position with respect to the substrate 21 so that the thermal spray material 19 in the plasma jet 20 is applied to the outer surface of the main body 212 . to form the film 23 in a layered manner.

As shown in FIG. 1 , the jig 22 is driven by a motor 222 and the motor 222 is installed on the bottom wall 111 of the thermal spray booth 11 . Similarly, on the bottom wall 111 , two cooling nozzles 24 are supported on the left and right by support members 25 . As shown in FIG. 2 , the two cooling nozzles 24 are arranged symmetrically with respect to the axis 141 of the thermal spray nozzle 14 near the nozzle head 143 . At the tip of the cooling nozzle 24, a gas outlet 241 is formed in the shape of a slit extending in the rotation axis direction of the substrate 21 (see FIG. 1). It is jetted toward the ceramic substrate 21 from the periphery of 20 .

Also, the cooling nozzle 24 gathers the thermal spray material 19 in the plasma jet 20 onto the substrate 21 on the jet of air 26 . In this embodiment, as shown in FIG. 4( a ), the axes 242 of the two cooling nozzles 24 cross each other obliquely at a position (intersection point P) closer to the thermal spray nozzle 14 than the base material 21 . The angle θ between the axis 141 of the thermal spray nozzle 14 and the axis 242 of the cooling nozzle 24 is preferably 35° to 60°. If the angle θ is less than 35°, the air 26 disturbs the flow of the plasma jet 20 and causes the film thickness to decrease. Moreover, if the angle θ exceeds 60°, the amount of air reaching the substrate 21 decreases, the cooling effect decreases, and cracks occur.

FIG. 4B shows test conditions for evaluating the relationship between the arrangement of the cooling nozzles 24 and the cracks in the substrate 21 and the film thickness of the coating 23 . In this test, the distance A from the center of the base material 21 to the intersection point P, the distance B from the intersection point P to the gas outlet 241 of the cooling nozzle 24, and the angle θ were changed, and four conditions "i" to "ni" were applied. set. Then, as shown in FIGS. 5(a) and 5(b), cracking of the substrate 21 and film thickness of the film 23 were evaluated by changing the amount of air under each condition. As a result, when the amount of air was 20 L/min or more, cracks did not occur in the substrate 21 under all conditions. Condition "I" can be said to be suitable for high-speed processing of the film 23 because no cracks occur at an air flow rate of 25 L/min and the film thickness is sufficient. In the condition "lo", the distance B is shorter than in the condition "i", so as shown in FIG. do.

As described in detail above, according to the plasma spraying apparatus 10 of this embodiment, as shown in FIG. The coating 23 is cooled by air 26 . Therefore, the base material 21 can be made to generate heat at a uniform temperature in each part, the difference in thermal expansion can be reduced, and cracking of the ceramic base material 21 can be suppressed. In addition, since the air 26 is jetted obliquely from both sides of the plasma jet 20 toward the base material 21, the thermal spray material 19 is collected on the base material 21 side on the jet stream of the air 26, and the film 23 is formed to a sufficient thickness. can be processed in a short time. Gases including the plasma working gas 15 and the cooling air 26 are recovered in the thermal spraying booth 11 and then discharged to the outside through an exhaust duct 27 (see FIG. 2).

(Other embodiments)
The present invention is not limited to the above-described embodiments, and as exemplified below, the shape and configuration of each part can be changed as appropriate without departing from the scope of the invention.
(1) Using various parts, products or articles other than sensor parts as the ceramic base material 21 .
(2) Forming the film 23 on the outer surface of a hexagonal prism, an octagonal prism, or more polygonal prisms.

(3) In the above embodiment, the thermal spray nozzle 14 sprays the plasma jet 20 laterally toward the substrate 21 held vertically. may inject the plasma jet 20 from above or below.
(4) The number of cooling nozzles 24 is not limited to two, and three, four or more may be arranged around the thermal spray nozzle 14 .

(5) The plurality of cooling nozzles 24 should be vertically symmetrically arranged with respect to the axis 141 of the thermal spray nozzle 14 .
(6) A single wide cooling nozzle having a symmetrical shape with respect to the axis 141 of the thermal spray nozzle 14 is used, and a relatively large amount of air is injected from both ends in the width direction, and a relatively small amount of air is injected from the central portion in the width direction. Spraying onto the substrate 21 .

10... Plasma spraying device, 14... Thermal spraying nozzle, 19... Thermal spraying material,
20... plasma jet, 21... base material, 22... jig, 23... film,
24... cooling nozzle, 26... air.

Claims (3)

a jig (22) for rotatably holding a ceramic substrate (21);
a thermal spray nozzle (14) that directs a plasma jet (20) containing a thermal spray material (19) toward the substrate while the substrate is rotating to form a coating (23) on the outer surface of the substrate;
It has slit-shaped gas outlets (241) that are arranged symmetrically with respect to the axis (141) of the thermal spray nozzle and extend in the direction of the rotation axis of the base material, so that cooling gas (26) is supplied during rotation of the base material. a plurality of cooling nozzles (24) that inject from the periphery of the plasma jet toward the substrate;
with
axes (242) of the plurality of cooling nozzles intersect each other;
When comparing the distance from the position where the axes of the plurality of cooling nozzles intersect to the substrate and the distance from the position where the axes of the plurality of cooling nozzles intersect to the thermal spray nozzle, the distance between the plurality of cooling nozzles The distance from the position where the axes intersect to the substrate is smaller, and in the projected view of the substrate in the axial direction, the position where the axes of the plurality of cooling nozzles intersect is the outer diameter of the jig. A plasma spray device (10) within range. 2. The plasma spray apparatus of claim 1, wherein the substrate has an outer surface comprising a cylindrical surface or a conical surface. 3. The plasma spraying apparatus according to claim 1, wherein the thermal spraying nozzle is provided with a variable position relative to the substrate.

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