JPH01281A - overlay coating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the provision of overlay coatings that bond thermal barriers onto substrates. Although the above-mentioned overlay coatings are particularly used on components exposed to high temperature environments where corrosion and erosion are likely to occur, the primary, but not necessarily the only, application of the above-mentioned coatings is on components of gas turbine engines, especially gas Turbine combustion tube products,
This applies to stationary blades, rotor blades, and guide vanes.

Conventional Techniques Using a plasma deposition process on a suitably prepared support surface, MCrAj! first spray coating a protective layer consisting of Y (where M is nickel or cobalt, or a suitable metal such as nickel and cobalt);
A bonded layer of metal is then spray coated by a flame deposition process which produces significantly coarser particles in the deposit than those in the protective barrier, and then a thermal barrier of refractory is coated by a plasma deposition process. It has been proposed to produce overlay coatings by spray coating.

PROBLEM SOLVED BY THE INVENTION Although this procedure is generally satisfactory, it has some non-ideal aspects. For example, flame spraying complex internal surfaces can be difficult and expensive.

Means for Solving the Problems According to the invention, a metal matrix M containing particles of CrA1M2 (where Ml is Ni or Co or both, M2 is y, si, T; Hf, Ta or a rare earth element) forming a protective layer by electrolytic or electroless deposition of a composite of one or more of The overlay coating on the support is then obtained by spray coating a thermal barrier of refractory material by a plasma deposition process.

The present invention thus differs from those previously proposed in that both the protective layer and the bonding coating are plated rather than flame sprayed.

The production of M CrAIM2 layers by plating has already been proposed in GB-2,167,446-A, which aims to produce coatings that are subsequently modified by heat treatment, the specification of which It emphasizes that strict control must be exercised, and the generally proposed particle size requirements are such that at least 99% (by weight) of the particles in the deposited coating are less than 25 μm or at least 9
It is said that 5% is between 3.0 and 13.6 μm. The specification states that electrodeposition produces coatings with highly desirable surface finishes. Plating is well known for producing coatings with smooth, even glossy surfaces, and the bonding of particles of this size to the deposited matrix further provides a relatively smooth surface. Sprayed MCr/M! Since the Y coating has an undesirably rough surface, a thermal barrier with sufficient adhesion can be achieved by spray-coated MCr.
It cannot be applied directly to the AjY coating. A bonded coating was needed that was spray coated with coarse particles. Therefore, it is thought that composite plating would be completely unnecessary when preparing the substrate for the thermal barrier. Most surprisingly, however, a plated M CrAIM2 coating followed by a plated adherent coating containing larger particles yielded an ib satisfactory substrate, and on top of that there was quite sufficient adhesion between the layers. It has now been discovered that the thermal barrier can be applied by spray coating while maintaining the thermal barrier properties. Thus, a plated anchoring layer is used to create a rough anchoring surface, which
This is something quite contrary to the commonly accepted property of plated coatings, which is one of smoothness.

Preferred components of the adhesive coating are the same as or similar to those of the protective layer, which, in addition to providing an adhesive function, is suitable for operating conditions similar to those for which the retention layer of the undergarment is provided. This is because the coating is exposed.

Suitable components and methods for applying the protective layer are those described in GB-2,167,446-A, supra; further details of the apparatus and methods that may be used can be found in GB-2 See 014.189-A and US-4,305,792. The apparatus and method described above can be used to apply bond coatings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND OPERATION Although the present invention may be implemented in a variety of ways, one particular overlay arrangement on a gas turbine will now be described for purposes of illustration.

The wing is first subjected to a suitable preparation process for plating; in one example, it is soaked in a cyanide cleaner for two minutes, followed by a water rinse, and then soaked in a ferric chloride etch solution. Etched by immersion in water for 30 seconds, followed by rinsing with water for 3 minutes at a current density of 3.5 A per dm2.
A nickel strike is applied by placing it in a nickel bath.

The vane is then held in a tampering barrel as described in GB-2,014,189-8 and connected to the cathode contact. CoN1CrA to a thickness of 0.076 to 0.127 mm using the technique described in GB-2,014,189-B.
IY coating is applied to the father-in-law, but the bath is CON
i plating solution, the particles weigh 1rcr60SAi40
．． CrAj! containing a proportion of Y1.7! It is Y. The particle size distribution has a maximum of 5% (by weight) below 5 μm, 10-15% (by weight) below 10 μm, and 35-55% (by weight) below 20 μm. Another particle size distribution is 7.7% (wt) below 5μm, 56% (wt) below 10μm, 20μm
94 (weight)% for less than m, 99 (weight) for less than 30 μm
This is the maximum value of %.

The plate with the protective layer is removed from the apparatus and cleaned, then CrAj! containing the same cobalt plating solution and having the same composition as used for the protective layer but with a different particle size distribution as described below. It is placed in the apparatus described in UK Patent Application No. 2182055, in which Y particles are charged into the apparatus. If there is a delay in moving from the first M, CrAxY coating to the second fixed coating process step, the surface of the component will be immersed in a ferric chloride etch solution and a nickel strike similar to the first pretreatment. It may be reactivated by The particle size distribution is such that for particle sizes above 150 μm it is less than 1% of the powder and for particle sizes less than 38 μm it is less than 15% of the powder. Plating is carried out to produce a bonded coating with a thickness of 0.025-0.15M.

The wings are then removed and cleaned. The coating is then vacuum heat treated to effect adhesion of the surface powder to the remaining deposit. For example, the blade may be treated at 1115°C for 2 hours, or in the range 1050-1100°C for 2 hours, or in the range 900-1200°C, for a maximum of 2 hours at 1200°C or a minimum of 1/4 hour at 900°C. You can also. A thermal barrier is then sprayed onto the bonded coating by a plasma flame deposition process. ``This coating consists essentially of 7-9% Y2O3 by weight, up to 1.
5% Si0. 0.5% CaO10.3% Mob
, 0.4% Fe2O3, 0.2% Al2O3 and 0.2% rho, . . . 8% yttria stabilized zirconia with the balance ZrO2. Particle size distribution is up to 10% for particle sizes greater than 74 μm and 65-10% for particle sizes greater than 44 μm.
0%, and for those less than 44 μm, the maximum is 25%. Instead of performing the vacuum heat treatment after depositing the adhesive coating, it may be performed in the same manner after depositing the thermal barrier.

As an alternative to the method described in GB-2,014,189-8, our UK Patent Application No. 85265
The protective layer and the adhesive coating can also be applied by the apparatus and method described in No. 46 (Publication No. 2182055).

During thermal cycling tests on paddle-shaped specimens coated on one side with the method described above according to the invention and moved in and out of the frame to increase the surface temperature to 1050° C. for 2 minutes and decrease it for 2 minutes, This test piece is
It successfully withstood 1000 thermal cycles, where the typical commercially acceptable level is 500 thermal cycles.

Claims (4)

[Claims] (1) A method of producing an overlay coating on a support, comprising: 1) a metal matrix M_1 containing particles of CrAlM_2, where M_1 is Ni or Co or both; M_2 is Y, Si, Ti, Hf; 2) forming a protective layer by electrolytic or electroless deposition of a composite of one or more of Ta or rare earth elements); 3) forming a bonded coating by electroless deposition; and 3) spray coating a thermal wall of refractory material by a plasma deposition process. (2) In the method according to claim 1, while the adhesive coating has a particle size larger than the particles of the protective layer,
How to make it have the same composition. (3) In the method according to claim 1 or 2, the particle size distribution of the particles of the protective layer is less than 5 μm and 5 (
weight)%, 10 to 15 (weight)% less than 10 μm, 20
A method having a maximum value of 35 to 55% (by weight) below μm. (4) In the method according to claim 3, the particle size distribution of the particles of the adhesive coating is 1 (weight) when it exceeds 150 μm.
% and a maximum value of 15% (by weight) below 38 μm.