GB2109417A

GB2109417A - Flame-spraying material

Info

Publication number: GB2109417A
Application number: GB08232442A
Authority: GB
Inventors: Wolfgang Simm; Hans-Theo Steine
Original assignee: Castolin SA
Current assignee: ECG Immobilier SA
Priority date: 1981-11-16
Filing date: 1982-11-12
Publication date: 1983-06-02
Also published as: DE3241377A1; DE3241377C2; FR2516550B1; CH648357A5; FR2516550A1; GB2109417B

Abstract

A boron-containing matrix alloy is mixed with an additive material of higher melting point, such as molybdenum, the particles of the additive material being spherical, in the grain size range from 20-150 mu m and constituting 30-80 percent by weight of the mixture. A protective layer or coating produced therefrom by flame-spraying, with simultaneous fusion, provides very good anti-friction properties with simultaneously a very high resistance to wear.

Description

SPECIFICATION Flame-spraying material The present invention relates to a flamespraying material which is in the form of a mixture of a pulverous boron-containing matrix alloy with a melting point below 1 0000C with particles of a metallic additive material having a melting point above 1 500 C.

Flame-spraying materials are already known, which are intended more especially for producing wear-resistant protective coatings on metallic substrates and which consist of a mixture of a boron-containing matrix alloy with additive materials, such as molybdenum, tungsten, tungsten carbide, etc.

Usually, the particles of the additive material are present in any arbitrary granule form, which may be irregular and more especially angular to flake-like and the grain size varies in the range below 20 ym.

The coatings are usually applied by plasma spraying or flame-spraying, with or without subsequent fusion.

However, it has been found that the wear resistance and the anti-friction properties of the usual coatings are not satisfactory and sometimes even the corresponding machine parts may be destroyed.

The present invention seeks to provide a flamespraying material of the type initially referred to, which permits the production of protective coatings with substantially improved properties as regards wear due to friction and sliding movements with metal-metal contact and consequently results in a longer life of the coated parts.

According to the invention, we provide flamespraying material in the form of a mixture of pulverous, boron-containing matrix alloy with a melting point lower than 1 0000C with particles of a metallic additive material with a melting point higher than 1 500 C, wherein the particles of the additive material are spherical, are in the grain size range from 20 to 1 50 ,um and the proportion of the additive material amounts to 30 to 80 percent by weight of the mixture. Preferably the proportion of the additive material amounts to 40 to 60 percent by weight of the mixture. A preferred additive material is molybdenum. Further preferred additive materials are tungsten, tungsten carbide or a mixture of molybdenum and/or tungsten and/or tungsten carbide.The invention also includes the use of a flame-spraying material as defined above for the production on a metallic substrate of a protective coating or layer which is resistant to metal-metal sliding friction stress, wherein the protective coating is applied by flamespraying of the material with simultaneous fusion on to the substrate. The invention also includes metallic parts or components which are coated in accordance with this process.

When a protective coating of the type as initially referred to is applied or melted on the surface of the particles of additive material, that is to say, at the boundary layer with respect to the matrix alloy, hard boride phases are formed, which lead to a strong embrittlement and, in operation, can even cause these particles to break away from the coating. This is more especially the case when the particles have sharp edges or are even of flake-like form, or the grain size of the particles is so small that, with the thermal coating process which is chosen, the hard boride phases completeiy permeate the incorporated particle or the edge portions thereof.

It has now been found that, by the use of spherical particles of relatively large diameter, i.e.

of 20-1 50 Mm, advantageously of 35-1 50 ,um, the formation of boride can be restricted to a thin surface layer of the particles and takes place very uniformly thereon, and that, in addition, by having a proportion of 30 to 80 and advantageously of 40 to 60 percent by weight of the additive material in the mixture, extremely good properties as regards wear and sliding properties can be produced.

The accompanying Figure shows the photomicrngraphic of the ground surface of a protective coating according to the invention, which consists of spheroidal molybdenum particles 1 with a grain size of 45-88 ym in a matrix alloy 2 of, in percent by weight, 1 SB, 2.4Si, 2Fe, 12Cr, the remainder Ni. A thin molybdenum boride layer 3 is to be seen on the pheriphery of the molybdenum particles.

The matrix alloy powder had a grain size in the range of 20-125 Mm and the proportion of the molybdenum particles amounted to 30 percent by weight of the mixture.

The coating was applied in a layer with a thickness of 3 mm and with simultaneous fusion to a base member consisting of steel of the type CrMo4, using the flame-spraying process known under the Trade Name "EUTALLOY process" of CASTOLIN S.A. It was shown that the coating is capable of being used, as regards sliding friction, up to a pressure of 5 kg/mm2, whereas a breaking away of the molybdenum particles already occurs with a frictional pressure of 1 kg/mm2 when using conventional protective coatings of similar types.

It was found that particularly good results are obtained when flame-spraying with simultaneous fusion, since the time of contact of the particles of added material in the molten matrix alloy is in this case comparatively short, as a consequence of which there is established a very weak and uniform diffusion of the boron on the surface of the particles, with formation of boride phases.

With a subsequent fusion procedure, this contact time is substantially longer, whereas with a layer or coating produced by plasma spraying or flame spraying without fusion, there is established a less satisfactory metallic bonding thereof with the base material and also between the matrix alloy and the incorporated particles of the additive material.

Molybdenum is the preferred additive material for most uses, for which good anti-friction properties are required. However, also tungsten, tungsten carbide or mixtures of various additive materials can be used in the flame-spraying materials according to the invention.

Advantageously employed as matrix alloys are alloys having the following compositions, in percentages by weight: (1) 1-4 B 1.5-5 Si 0--10 Fe 0--20 Cr 0--10 W and/or Mo 0--5 Cu remainder Ni (2) 0.5-3.5 B 0.5-4.5 Si 0--5 Fe 5-30 Cr 0--12 W and/or Mo 30-40 Ni remainder Co It is apparent from the foregoing that the invention makes possible the formation on metallic substrates of a layer or coating with very good anti-friction properties and, at the same time, very high resistance to wear, more especially on machine parts which are subjected to severe stressing due to sliding friction in contact with metallic contacting members, as a result of which the effective life of the said parts can be substantially lengthened.

Claims

1. Flame-spraying material in the form of a mixture of a pulverous, boron-containing matrix alloy with a melting point lower than 1 0000C with particles of a metallic additive material with a melting point higher than 1 5000 C, wherein the particles of the additive material are spherical, are in the grain size range from 20 to 1 50 ssm and the proportion of the additive material amounts to 30 to 80 percent by weight of the mixture.

2. Flame-spraying material according to claim 1, wherein the proportion of the additive material amounts to 40 to 60 percent by weight of the mixture.

3. Flame-spraying material according to claim 1 or 2, wherein the matrix alloy has the following composition, in percent by weight: 1-4 B 1.5-5 Si 0--10 Fe 0--20 Cr 0--10 W and/or Mo 0--5 Cu remainder Ni

4. Flame-spraying material according to claim 1 or 2, wherein the matrix alloy has the following composition, in percent by weight: 0.5-3.5 B 0.5-4.5 Si 0--5 Fe 5-30 Cr 0--12 W and/or Mo 30-40 Ni remainder Co

5. Flame-spraying material according to any one of the preceding claims, wherein molybdenum is used as an additive material.

6. Flame-spraying material according to any one of the preceding claims, wherein tungsten, tungsten carbide or a mixture of molybdenum and/or tungsten and/or tungsten carbide are used as additive material.

7. Use of a flame-spraying material according to any one of the preceding claims for the production on a metallic substrate of a protective coating or layer which is resistant to metal-metal sliding friction stress, wherein the protective coating is applied by flame-spraying of the material with simultaneous fusion on to the substrate.

8. Metallic components, which are provided with a protective coating produced in accordance with claim 7.

9. Flame-spraying material according to claim 1, substantially as described herein.

10. Flame-spraying material substantially as described herein with reference to the drawing.

11. A process for applying flame-spraying substantially as described herein.

1 2. Metallic components, provided with a coating derived from the material of any one of claims 1 to 6,9 or 10.