JPS6119351A - Article forming abrasive surface and manufacture thereof - 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 TECHNICAL FIELD This invention relates to abrasives, particularly thin layer abrasives deposited on superalloys used at elevated temperatures.

BACKGROUND OF THE INVENTION Gas turbine engines and other axial flow turbomachines have rows of rotating blades contained within a generally cylindrical case. It is highly desirable to minimize leakage of gas or other working fluid around the blade tips close to the case.

It is known that this leakage is minimized by blade and sealing systems in which the blade tips rub against seals mounted on the interior surface of the engine case. in general,
The blade tips are made harder (and more aggressive) than the seals, so the blade tips cut into the seals when these parts of the engine come into contact with each other during operation.

In previous systems of the type described above, the blade tip was often a superalloy material with a hard surface and the seal was a metal with a moderate wear tendency.

For example, porous powdered metals were used. Now, however, U.S. Pat.
It has been found that seals comprising ceramics are desirable, as shown in U.S. Pat. No. 903 and U.S. Pat. Ceramic coated seals are significantly harder than conventional metal seals, and as a result, conventional blade tips lack the ability to abrade the seals.

Accordingly, an improved blade tip is disclosed, most particularly in U.S. Pat. A blade tip of the type described has been developed in which silicon carbide particles with an average standard diameter of 0.20 to 0.76n are coated with a metal oxide such as alumina and powdered metal still remains. are incorporated into nickel- or cobalt-based alloys by casting techniques. Particles with a volume percentage of 30-45% containing powdered metal compactly are produced and placed at the tip of the blade by diffusion pumping, liquid phase pumping or filtering. Bonded by attaching.

However, abrasives produced by the above method have some inherent properties. In particular, metal parts can only be manufactured to extremely minimal thicknesses, typically 1-2 days thick. Typically, abrasive tips are manufactured to the cross-sectional shape of the tip of a turbine blade body and machined into a flat surface after compaction or casting. Similarly, the blade tip is machined into a flat surface to receive the abrasive. Such flat machining is a necessary practical limitation in order to obtain a good close fit and minimum weld thickness on the order of 0.05 m. If this is not done, adequate bond strength at operating temperatures of 1100°C will not be achieved. After pounding the abrasive onto the blade tip, the plurality of blades are assembled into a fixture configured to rotate with the engine disk. They are then ground to a cylindrical or conical surface that matches the inner surface of the engine case seal. As a result of this process, the abrasive initially has a substantial thickness that must be ground to a substantial degree. Particles are often expensive and therefore the method is also expensive. Second, since the joint surface is flat and the final finished shape of the abrasive tipped blade is cylindrical or conical,
As shown in FIG. 9, there is a variation in abrasive thickness across the blade tip. While known blades are useful, it is more desirable that the abrasive portion of the tip have a uniform thickness across the curve. It is also highly desirable to minimize the amount of grid that must be used during the manufacturing process. This is because the grids must be of high quality and their manufacture, including the oxide coating process, is expensive.

It is an object of the present invention to form a thin, uniform layer of abrasive on the tip of the blade that is suitable for use at temperatures near and above 1100°C. Abrasive thin layers carrying particles are known, although they are not suitable for use at such high temperatures. For example, coated abrasives made from alumina, silica, and silicon carbide are common products, as are metal-plated diamond and cubic nitride-boron grinding wheels. Sprayed fused or unfused layers of metal are well known in the metallization art. For example, US Patent No. 3+
248+ 189 and 4,386', 112. However, both metal spraying grids and base metal processes are inherently inadequate in that only a portion of the sprayed material actually hits and adheres to the surface; these are particularly , making the abrasive formation of typical turbine blade tips of a size of approximately 6/50 mm difficult, for example.

The prior art particularly relevant to the present invention is as follows.

Silicon carbide particles are described in U.S. Patent No. 3,508,8
No. 90 and No. 3,377.624, parts are bonded using an organic adhesive and then surface coated with aluminum or other metal. U.S. Patent No. 3.779
．． No. 726 describes a method of manufacturing metal-abrasive tools containing silicon carbide and other grids by encapsulating the grid within a porous metal coating and then using an encapsulation layer with another metal to integrate the particles. A method of impregnation is described. US Pat. No. 4,029,852 describes a method for producing non-skinned surfaces by placing a grid on the surface and spraying molten metal droplets onto it. This U.S. Patent No. 4,0291
The '852 invention is directed to relatively large products, such as stair treads, as opposed to metal bonded abrasives and the fine products that characterize the present invention. U.S. Pat. No. 3,871,840 describes how the properties of metal-bonded abrasives made in various ways are improved by encapsulating a grid within a pure metal envelope. ing.

The previously described abrasives, which are comprised of particles and metal structures and are attached to turbine blade tips by a welding process, have exhibited useful abrasive properties. However, although it is desirable to reduce the abrasive thickness to the minimum thickness required for a robust tip, such minimum thickness may not be achievable depending on the pounded abrasive tip due to the manufacturing practical issues discussed above. It cannot be done. At the same time, past experience has shown that materials commonly available for other applications, including those described in the aforementioned U.S. patents, are insufficiently robust, even though they may provide the desired minimum thickness. Therefore,
Research and development needed to be done to produce superalloy turbine blades with the desired abrasive tips.

DISCLOSURE OF THE INVENTION An object of the present invention is to form a thin abrasive layer on the surface of a metal object. In particular, it is an object of the present invention to form a very lightweight yet robust abrasive material on airfoil for turbomachinery. That is,
It is desirable to produce ceramic particles and metal abrasives using as few particles as possible. For high temperature applications, abrasives must be made of oxidation-resistant materials, especially superalloy base metals, and the abrasive must be well bonded to a superalloy "substrate" to withstand thermal and mechanical stresses. No.

According to the invention, the article has a single layer of ceramic particles on its surface. The particles are in contact with the surface of the substrate;
It also extends predominantly through the surrounding base metal to the free machined surface. Also, when the machined surface is parallel to the surface on which the abrasive is placed, the particles have equal lengths and are placed on the surface in the most effective manner. To obtain optimal performance from the abrasive, the particles are closely but evenly spaced. but,
The particles are carefully sized and arranged such that at least 80% of the particles do not touch each other.

Thus, the presence of the surrounding matrix means that the particles are better implanted into the abrasive and that the abrasive is better bonded to the substrate.

In accordance with the present invention, abrasives are made from ceramics having a particle aspect ratio of 1.9:1 or less, preferably around 1.5:1. This means that the particle has 1CI112 on the particle surface.
approximately evenly spaced at a density of 33 to 62, preferably 42 to 53, and also 10 to 20 (volume percentage).

In a preferred embodiment of the invention, abrasive materials are applied to the tips of superalloy turbine blades using sintering, plasma arc spraying, and machining. Ceramic particles are those that do not interact with the matrix material at elevated temperatures. For example, alumina-coated silicon carbide particles have been used. The particles were further clad with a sinterable material, such as nickel. The particles are placed on the surface and heated to a sintering temperature, thereby alloyingly adhering the nickel layer to the substrate. A superalloy matrix is then deposited over the particles, usually by a "line-of-sight" process (in which the deposited material moves linearly toward the surface).

Cavities are created near the irregularly shaped particles on the surface, and then a process such as true static pressing is used to densify the matrix around the particles. The result is a dense superalloy matrix containing ceramic particles with regions of interdiffused metal at the periphery (relatively deficient in the composition of the matrix material and regions relatively enriched in the composition of the cladding material). A metallurgical structure is obtained which can be attached.

When the abrasive is placed on the tip of the blade that interacts with the ceramic seal, the matrix material is exposed to the free machined surface of the abrasive such that 10-50% of the particle length, measured from the substrate, is exposed. partially removed from This improves the abrasive's ability to cut ceramic seals.

The present invention has a relatively small airflow oil tip.
.

Above the cambered surface, the blade tip is cut into a ceramic anti-friction seal that protects it from wear.
It is useful for depositing abrasive materials that achieve one objective of the present invention, such as withstanding high temperatures and thermal stresses.

The above and other objects, features and advantages of the present invention will become more apparent as preferred embodiments thereof are described in detail below with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a typical advanced gas turbine engine turbine blade tip constructed from a single crystal nickel alloy as described in U.S. Pat. No. 4,209,348. In this case, it is simply called “abrasive”.
alumina-coated silicon carbide particles of the type disclosed in U.S. Pat. No. 4,249,913 are disclosed in the present invention. No. 4,249,913, the disclosures of which are incorporated herein by reference. The invention is equally applicable to other materials. As indicated in the specification, alumina coatings on silicon carbide particles are particularly useful because they prevent interactions between the silicon carbide and the surrounding base metal. This can occur during medium and high temperature use and can reduce the ability of the silicon carbide particles to perform abrasive functions. Preferably, the alumina coating is between 0.010 and 0.020 mm thick. , also deposited by a commercial chemical vapor deposition process.

The matrix is a metal that can be bonded to the particles and the substrate. The base material, in the best embodiment of the invention, is a heat resistant alloy, i.e. commercial alloys Inconel 600, Inconel 625.
, Hastelloy
R-M2O3 and Inconel 718 are alloys based on Ni, Co or Fe that are strengthened by gamma prime precipitation. Both types of alloys are available in a number of compositions with varying properties, namely Ni, Co, Fe, Cr and F.
The latter two elements particularly characterize them, resulting in oxidation resistance.

Preferably, the superalloy matrix has a weight percentage of 21 to 25 C
r, 4.5~? Al, 4~l OW, 2.5
~7Ta, 0.02~0.15Y, 0.1~0.3
C, has a standard composition of residual Ni. Other useful materials are 18-30Cr, 10-3ONi+Fe by weight percentage.

5-15 W+Mo, 1-5Ta+'Cb, 0.
05~0.6C13,5・~80A1.0.5~20H
f and 0°02~0. It is a cobalt-based alloy with a standard composition of IY and residual Co.

A typical turbine blade configuration is shown in FIG. The blade 20 consists of a root section 22 and an airfoil section 24. An abrasive layer 26 is applied to the blade tip 28 by the method of the present invention. The surface 30 of the abrasive tip is finished as a rotating cylindrical surface with a standard radius R and circumference. Radius R is the radius of the bladed turbine wheel and is also the inner radius of the engine case that typically contains the bladed turbine wheel. The blade axis that coincides with the radial direction is defined as its z-axis. The tip of the blade has an average camber line C, which is the standard centerline of the Aerofoil tip cross section.

9 and 10 show side views of the blade tip as it appears when looking along line C toward line C when line C is spread out into two planes. FIG. 10 shows the appearance of the sill 26 of FIG. 8 having a constant thickness. Blade base 2
8 and the abrasive surface 30 are both curved. These curved surfaces are complex due to the surface defined by the interaction of the cambered and cylindrical surfaces when stretched. A similar view of a known blade tip constructed in the manner described in the background section is shown in FIG. The outermost surface 30a of the abrasive is identical to the curved surface 30 shown in FIG. 10, and the surface 32a of the blade base 28a is flat. Therefore, the radial or biaxial abrasive thickness varies across the airfoil camber length C. There is also a clear tendency for metal deficient grids to exist at the leading and trailing edges. Also, in accordance with the present invention, in FIG. 10, the abrasive consists of a single layer of particles, whereas the known layer requires a large number of glycides near the central portion 35a of the camber line length. Also, known abrasives typically have adhesive seams 31.

The process steps for forming a thin abrasive tip are partially outlined in FIGS. 1-7 and described further below. 1-4 show the profile of the tip of a gas turbine blade, and FIGS. 5-7 show a portion of the tip in more detail, both viewed along the line. There is.

The abrasive tip of the present invention is intended to interact with ceramic abradable seals, as disclosed in a few of the US patents mentioned in the Background section. There are several unique aspects of the abrasive that have been discovered to be necessary for good performance and that differ from known advanced abrasives. These aspects include the composition of the particles and the matrix, the dimensions of the particles, the density placed at the tip of the blade (both with respect to spacing and volume percentage within the matrix), the total thickness of the abrasive layer, and the degree to which the particles are actually encased by and placed within the matrix. The parametric limitations advocated herein are particularly relevant in U.S. Pat.
This is the result of experience with an abrasive comprising a superalloy matrix and alumina-coated silicon carbide particles as disclosed in the US patent application. However, many of the aspects are also suitable for other particles, especially those relating to mechanical aspects.

Abrasive thickness must be limited and must comply with particle sizing. First, abrasives include a single layer of particles as shown in FIG. A single layer of abrasive particles is important to keep the mass of abrasive material at the tip to a minimum. Empirical tests and calculations have shown that for an abrasive tip to be effective when interacting with a ceramic seal, the particles must exert appropriate force, 7)
It has been found that approximately 10-50% of the base material must be removed to ensure that it is not easily removed from the blade tip. If more is removed, the remaining matrix will be insufficient to hold the particles under the loads during use.

The AZ-axis thickness of the preferred tip abrasive according to the present invention is about 0.38±0.03n, and for such thickness the particle size is US Sieve Series No.

consistent with a sieve between 35 and 40 (typically 0.42±0.50). Of course, even a common sieve will result in a distribution of particle sizes, especially since typical ceramic particles are irregular. Some of the particles are No. 40
smaller than the sieve size. However, the typical minimum particle size is 0.420, which means that the majority of the ceramics (0% or more) are abrasive as shown in Figures 3, 4, and 9. This reflects the fact that the free surface 44.30 necessarily extends through the matrix, in contrast to the prior art shown in FIG. 9 and the previously referenced patent. When an abrasive layer is desired, a US sieve series No. 20 (typically 0
．． It has been found effective to use larger particles up to 83 fi).

Typically, the matrix is deposited to a sufficient thickness to surround the particles, and the matrix and particle composite is then machined to finished dimensions. Thus, the majority of the particles have a machined length and are of equal length when the free surface is generally parallel to the desired substrate surface.

In the best embodiment of the invention, the particles are evenly and relatively closely spaced. The density is in the range of 33-62 particles per l cm2. Still 15-2
More than 0% of the particles are not agglomerated, ie they do not touch each other. Spacing between the particles is required for them to be properly surrounded by the matrix and properly adhered within the abrasive. In the present invention,
The majority of the particles are oriented parallel to the surface (i.e. 2
completely surrounded by the base metal (transversely to the axis). This means that at least 80%, and typically 90%, of the particles are surrounded by the matrix, apart from the coarse particles exposed by the finish on the side edges of the tip.

In order to obtain the above-mentioned composite with higher density and complete encapsulation, the present inventors also use true pressed silicon carbide particles of less than 1.9:1, preferably about 1.4-1.
We have discovered that it must have an aspect ratio of 5:1. Aspect ratio is the standard ratio of a particle's longest axis to its standard cross-sectional dimension. The inventor of the present application is the Quantay Mesotho Surface Analyzer (Cambridge Instruments Co., Ltd.)
Cambridge Instrument Ltd)
, Cambridge, UK) was used to measure the aspect ratio. This aspect ratio is in contrast to the typical particles used in known powder metal abrasive tips, which have an aspect ratio of 1.9 to 2.1 to 1. With such particles, when the particles are placed on a surface using the method of manufacture shown in Figure 1, their longer lengths are naturally placed approximately parallel to the surface, so that excessive agglomeration may occur. A lump formed. Such high aspect ratio particles tend to be less likely to adhere to a desired height than more equiaxed particles and also prevent high densities from being achieved.

As mentioned above, the particles are enclosed within the metal matrix. When the abrasive is machined into a flat surface as shown in Figure 3 prior to removal of a portion of the matrix, the particles typically account for about 10-20% of the total abrasive, preferably 15%. (volume percentage). This is a lower concentration than that disclosed in US Pat. No. 4,249,913. It has been found that concentrations above about 20% tend to cause abrasive material fatigue due to cracking. Concentrations below 10% tend to result in inadequate abrasive properties.

The critical dimensions, aspect ratios and densities mentioned above must be achieved to obtain the desired cutting action. Because the typical tip of a turbine blade is narrow, very few particles are present within this region. The purpose of the present invention is to
The goal is to form a full line of particles across the width of the blade when viewed closely along the line in FIG.

With the abrasive feature according to the invention, this is achieved in 90% of the blades. The remainder may have a small number of open spaces due to particle loss between the time of depositing the particles on the part and the time the part is finally ready for use.

FIG. 1 shows how the particles are initially placed on the surface 32 of the substrate 28 to which they are subsequently to be permanently adhered. Prior to placing the silicon carbide particles on the surface, the particles were coated on the outside of them with U.S. Pat. No. 4,249
, 913, and a cladding of a chemically applied metal such as nickel to a thickness of O,OO5 to O,'050 i++a. Methods for applying nickel coatings to ceramic particles are commercially available and described in U.S. Pat.
No. 20,410, No. 4゜291.089 and No. 4,
No. 374,173. If the ceramic particles are inherently resistant to reaction with the matrix, a narumina coating is not necessary.

Immediately before the particles are placed on the surface of the blade tip, a coating of polymer adhesive is applied to the surface, which can be subsequently evaporated at a temperature below 540° C., to hold the particles after attachment.

The inventors selected 1-20% (volume percentage) polystyrene in toluene. Particles are placed on a surface by first drawing the particles into a perforated plate that is provided with a vacuum, then placing a ramp on top of the surface and momentarily releasing the vacuum. It will be clear that other methods and adhesives can be used to place the particles.

Next, the blade with the organically treated particles is heated. It is heated to at least 1000° C., typically about 1080° C., for 2 hours in a vacuum of about 0.06 Pa using a heating rate of about 500° C. per hour in a vertical position. Other inert atmospheres may also be used. This process first vaporizes the polystyrene adhesive and then causes solid-phase ponding or sintering of the nickel cladding on the surface of the blade. The nature and location of the bond joint 34 is shown in FIG. 5 as it can be observed in metallurgical micrographs after removal from the furnace. Because of the irregular shape of the particles and the thickness of the metal cladding on the particles, the bonds 34 are relatively delicate and are only placed at points where the particles 33 are very close to the surface 32. When the matrix is a superalloy, it is undesirable to have large amounts of bond metal around the particles or bond them to the blade substrate. It is also undesirable to expose the substrate to temperatures above about 1800 DEG C., thus limiting the choice of cladding on the particles to materials that will form bonds under such conditions. Additionally, the cladding material must be compatible with, and tend to interact with, the substrate and the subsequently deposited matrix. These conditions nevertheless allow a variety of materials to be used. Preferably nickel, cobalt or mixtures thereof are used.

Alloy additives known to promote bonding may be included. In general, the metals of the cladding tend to be metals from the transition series of the periodic table when nickel, ferrous base matrix and base alloys are included. Under certain circumstances, a coating may be applied to surface 32 to enhance the desired adhesion.

The particles are then oversprayed with a layer of matrix material deposited by plasma arc spray to a thickness of about 1.1 to 1.3 meters as shown in FIGS. 2 and 6. Nickel-based superalloys as described above, such as 25Cr, 8W, 4Ta: 6Al 1. by weight percentage. O
Hf, 0. IY, 0.23C.

A superalloy with a residual Ni composition is used.

-400 US sieve series mesh powder is deposited by argon-helium plasma arc spray in a low pressure chamber. For example, Electro-Plasma (El
Commercially available equipment can be used, such as a 120 kW low pressure plasma arc spray system from electro-Plasma Inc. (Irping, Calif., USA). See also US Pat. No. 4,236,059. The blade is placed in a spray chamber evacuated to a pressure of 26 kPa or less. The oxygen level in the atmosphere can be reduced to 5'ppm by volume, for example, by contacting the atmosphere in the chamber with a reactive metal.
reduced to the level of The workpiece blade is placed in the plasma arc device such that the tip section is sprayed perpendicular to the axis of movement of the molten particles. The blade is suitably masked around its periphery to prevent stray spray from depositing on the sides of the blade.

Prior to the start of the actual deposition, the workpiece is simultaneously heated to at least 700°C by means of a high-temperature plasma arc gas.
It is typically heated to 850° C. and is simultaneously cathodized with respect to a ground electrode located in the vicinity of the plasma arc device or as an integral part thereof. A current of about 70 A is applied to a typical turbine blade tip for about 2 to 10 minutes to help remove any oxide layer that may have built up on the component. The purpose of the heating process is to increase the receptivity of the part to plasma arc spray, improve bonding, and reduce residual stresses that exist after the workpiece, including base metal and substrate, has cooled to room temperature. be. The abrasive thus has improved resistance to cracking and spalling.

The metal base material is 0.6 to 1.3 Tsuru, as shown.
Preferably, it is deposited to a thickness of 1.1 to 163 mm.

Preferably, the base metal is deposited by a physical process to a thickness and quality such that the layer of metal is impermeable to argon gas at elevated pressures, ie at least 130 MPa. This impermeability can be achieved with sufficient thickness of deposition by the plasma spray process described above.

Although the layer is impermeable, the sixth
It is characterized by some porosity as shown in the figure. In particular, pores 38 are present in the material on the surface of the particles, and voids 40 are present adjacent many of the particles. Cavity 40 is inherent in metal spray processes and is created by any "line-of-sight" deposition process or process in which the deposited material physically moves in a straight line. Other processes that may be used are physical vapor deposition processes.

See U.S. Pat. No. 4,153,005.

The part is then densified, preferably by isostatic pressing. Generally, this involves deforming the abrasive material past its yield or creep threshold at elevated temperatures. Preferably, the part is 1065 to close said holes and voids.
℃ and 138 MPa argon pressure. Other hot pressing processes can be used to solidify the matrix and also achieve densification and bonding purposes. After the base material is solidified, the part is cooled in the furnace and removed.

However, FIG. 7 shows in more detail how abrasive appears within a micrographically aligned sample. The superalloy matrix is dense and completely surrounds the particles. Also surrounding each particle 33 is a region 42 that is low in chromium, aluminum and heavier elements and rich in nickel compared to the composition of the base material. This is of course due to the nickel attached to the particles.
This is a result of the thalassodding layer and is a feature of the present invention.

The abrasive rough surface shown in FIG. 2 is then machined using conventional processes such as grinding to obtain the shape outlined in FIG. free surface 44
yields the two desired length dimensions T' that characterize the finished blade. The blade surface 44 is then contacted with an etchant or other substance that attacks the base material and removes portions thereof. For example, electrochemical machining as described in US Patent Application No. 517,315, dated July 26, 1983, may be used.

As will be appreciated, the present invention includes particles that are aligned along the surface of the article. Such two-dimensional manufacturing methods yield much more uniform and effective abrasions than conventional three-dimensional manufacturing methods that are performed by mixing with metal powder and solidifying. In the present invention, the free machined abrasive surface is characterized by a relatively uniform cross-sectional area of the ceramic (reflecting the largest to smallest size). This is in contrast to the widely varying cross-sectional area reflecting the maximum-to-zero particle size that characterizes known powder metal abrasives. Also, when a portion of the matrix is partially removed, the presence of particulate material at the original free surface of the present invention remains unchanged. However, in the prior art, some of the particles were lost and the amount of free surface ceramics was reduced because portions of the particles were only retained within the abrasive by the matrix from which they were removed.

Although the present invention has been described above with reference to specific preferred embodiments, it is understood that the present invention is not limited to these embodiments, and that various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of the drawing]

Figures 1 to 4 outline the sequential process by which particles are placed on the surface of a substrate, encapsulated within a matrix, machined into a flat surface, and machined into their final form. be. FIG. 5 is a more detailed view of a portion of FIG. 1, showing how the particles appear after being metallically bonded to the surface of the substrate. FIG. 6 is a more detailed view of a portion of FIG. 2, showing how the matrix surrounds the particles and includes pores when a "line-of-sight" deposition process is used. FIG. 7 is a more detailed view of a portion of FIG. 2, showing how the structure of FIG. 6 is transformed after high temperature pressurization to eliminate voids and create interdiffusion. FIG. 8 is a schematic diagram of a typical gas turbine blade having a nubular layer at the tip. FIG. 9 is a side view of a known abrasive blade tip showing changes in thickness and bonding. Figure 10 is a side view of the blade along the lines of Figure 8, showing how the particles are present in a single layer and how they extend slightly above the abrasive matrix material. It shows. 20...Blade, 22...Root part, 24...
Aerof oil part, 26... abrasive layer, 28
...Tip, 30...Abrasive tip surface, 32.
... Outermost surface, 33... Particle, 34... Bond joint, 36... Superalloy base material, 38... Hole, 40...
Vacant space, 44...free surface

Claims (4)

[Claims] (1) In an article consisting of a substrate on which an abrasive material consisting of a metal matrix and ceramic particles is adhered, a majority of the ceramic particles extend from the substrate surface through the matrix to the machined surface of the abrasive material. An article having an abrasive surface. (2) In an article shaped like a turbine engine airfoil with a curved tip surface to which an abrasive material consisting of a metal matrix surrounding ceramic particles is adhered, the majority of the particles are on a single layer. 1. An article having an abrasive surface, the abrasive surface resting on the abrasive surface, in contact with the tip surface, and extending approximately equal length through the matrix to the free surface of the abrasive. (3) In an article shaped like a turbine engine airfoil that is manufactured from a superalloy and has a curved tip surface to which is adhered an abrasive material consisting of a high temperature alloy metal matrix surrounding ceramic particles. The majority of the particles rest on a single layer, are in contact with the tip surface, and extend approximately equal lengths through the matrix to the free surface of the abrasive, with a ratio of 1.9 to 1. An article having an abrasive surface characterized in that it has an aspect ratio of: (4) a method of depositing an abrasive material consisting of particles and a matrix onto the surface of an article, the step of adhering a single layer of spaced ceramic particles having a metal cladding to the surface of the article; The process of adhering a metal cladding to a surface such that particles are adhered to the article and protrude from the surface at intervals, and the process of bonding a metal cladding to a surface such that particles are adhered to the article and protrude from the surface at intervals, and a layer of metal is applied to fill the spaces between the particles by means of a matrix material that inherently has voids. heating the article to an elevated temperature to densify the matrix and alloyingly bond it to the metal clad particles and the substrate; machining a surface on an abrasive material to a finished surface such that the abrasive material has a finished surface.