WO2010110873A1

WO2010110873A1 - Chrome-free coating for substrate

Info

Publication number: WO2010110873A1
Application number: PCT/US2010/000858
Authority: WO
Inventors: Michael W. Seitz
Original assignee: Seitz Michael W
Priority date: 2009-03-24
Filing date: 2010-03-24
Publication date: 2010-09-30
Also published as: AU2010229319A1; AU2010229319B2; KR101548553B1; CN102387870A; EP2414106A1; PL2414106T3; MX2011009089A; CA2756033A1; JP2012521496A; CN102387870B; CA2756033C; EP2414106B1; KR20120009422A; JP5275509B2; EP2414106A4

Abstract

A chrome-free mixture or alloy, preferably a composite wire is disclosed for producing a wear resistant and corrosion resistant coating on a substrate, for example by thermal spraying techniques. The physical properties of the coating are particularly suited for high-temperature erosion-corrosion environments. The resultant coating exhibits good hardness, toughness, and bonding characteristics. The composite wire comprises a metallic outer sheath and an inner core and produces a chrome-free coating comprising, in bulk on a weight basis, 60 to 90% of a base metal including at least 2% aluminum and/or silicon, 2 to 10% titanium, 2 to 10% silicon, and 2 to 10% boron.

Description

DESCRIPTION CHROME-FREE COATING FOR SUBSTRATE Technical Field

This invention relates to chrome-free metal coating compositions and thermal spray wires for producing same.

Background Art It was known prior to the invention that it is difficult to avoid chrome in a metal coating that offers high temperature corrosion resistance. Chrome is undesirable during the coating process because it poses human and environmental hazards.

Disclosure of Invention

In one embodiment of the invention, there is provided a composite of precursor materials for forming a chromium-free metallic coating. In another embodiment of the invention, the precursor materials are provided in the form of a composite wire. In a further embodiment of the invention, there is provided a chromium-free metallic coating as can be made from the wire.

Generally speaking, the chromium-free metallic coating precursor comprises a base metal constituent, a silicon constituent, a titanium constituent, and a boron constituent. The base metal constituent is present in amount of at least about 54% by weight. The base metal constituent comprises at least one base metal selected the group consisting of iron, nickel, cobalt, lead, zinc, copper, tin, and aluminum and always comprises at least about 1% by weight of alloyed aluminum and/or silicon, based on mass of the coating precursor. The silicon, titanium and boron constituents are each present in amount between about 1% and about 15% by weight.

The above constituents can be provided in a composite wire in accordance with another embodiment of the invention. The composite wire usually comprises a metallic outer sheath in the range of 70 to 95% by weight and an inner core in the range of about 5 to about 30% by weight. The metallic outer sheath preferably comprises at least about 70 weight percent of a base metal readily capable of being rolled and drawn into the sheath and at least about 2 weight percent alloyed aluminum and/or silicon. The inner core in one embodiment of the invention comprises in the range of about 15% to about 30% titanium, in the range of about 15% to about 35% silicon, in the range of about 20% to about 50% boron, and in the range of 0% to 15% carbon, all preferably in particle form.

The composite wire can be applied by thermal spray technique to produce the metallic chrome-free coating of the invention on a substrate. The chrome-free coating composition usually comprises, in bulk on a weight basis, about 60 to about 90% of base metal, at least about 2% aluminum, about 2 to about 10% titanium, about 2 to about 10% silicon, and about 2 to about 10% boron. The coating is high temperature wear and corrosion resistant.

Brief Description of Drawings

The drawing illustrates pictorially a composite wire in accordance with an embodiment of the invention.

Best Mode for Carrying out the Invention In the following description, all percentages given are weight percent, unless otherwise noted. The invention is described in terms of the precursor materials for forming the chrome-free coating, the precursor materials in the form of a composite wire, which is the preferred form of employing the precursor materials, and a coating as made by the wire.

Generally speaking, the chromium-free metallic coating precursor comprises a base metal constituent, a silicon constituent, a titanium constituent, and a boron constituent, in alloy, mixture or composite form. The base metal constituent is present in amount of at least about 54% by weight. The base metal constituent usually comprises at least one base metal selected the group consisting of iron, nickel, cobalt, lead, zinc, copper, tin, and aluminum and always comprises at least about 1% by weight of alloyed aluminum and/or silicon, based on mass of the coating precursor. The silicon, titanium and boron constituents are each present in amount between about 1% and about 15% by weight.

Usually, in the chromium-free coating precursor, the base metal is present in an amount of at least about 68% by weight and contains an aluminum and/or silicon component alloyed therein in an amount of at least about 2% by weight, based on mass of coating precursor. The silicon, titanium and boron are each present in amount between about 2% and 10 percent by weight.

Preferably, in the chromium-free coating precursor, the base metal constituent is present in an amount of at least about 76% by weight and is selected from at least one of iron, nickel, cobalt, and aluminum. The base metal constituent is a mixture or an alloy, preferably an alloy, and always comprises at least about 3% by weight of aluminum, based on mass of coating precursor. The silicon, titanium and boron are present, preferably as a mass in particle form, in amount between about 4% and about 7%, preferably as the inside of a composite wire formed from the base metal constituent.

The coatings of the present invention can be formed from composite wires as described herein by feeding the wires through a conventional arc spraying apparatus. Usually, the composite wire 10 comprises a metallic outer sheath 20 in the range of 70 to 95% by weight and an inner core 30 in the range of about 5 to about 30% by weight. In a preferred embodiment, the composite wire comprises a metallic outer sheath in the range of about 75 to about 85% by weight and an inner core in the range of about 15 to about 25% by weight. The metallic outer sheath preferably comprises at least about 70 weight percent of a base metal readily capable of being rolled and drawn into the sheath and at least about 2 weight percent alloyed aluminum and/or silicon. Aluminum can also be employed exclusively as the base metal. The inner core in one embodiment of the invention comprises in the range of about 15% to about 30% titanium, in the range of about 15% to about 35% silicon, in the range of about 20% to about 50% boron, and in the range of 0% to 15% carbon, all preferably in particle, preferably powdered, mixture form. The titanium, silicon and boron may be present as a mixture of compounds containing additional elements.

The base metal is preferably a relatively soft elemental metal or alloy, for example, at least one of nickel, iron, or cobalt. Nickel is preferred, and the outer sheath most preferably comprises an alloy of nickel and aluminum. Exemplary materials comprise in the range of about 70 to about 98 percent by weight of nickel and in the range of about 2 to about 30 percent by weight of alloyed aluminum and/or silicon, preferably in the range of about 85 to about 98 percent by weight of nickel and in the range of about 2 to about 15 percent by weight alloyed aluminum and/or silicon, and most preferably about 90 to about 97 percent by weight of nickel and in the range of about 3 to about 10 percent by weight of alloyed aluminum.

The inner core preferably comprises in the range of about 20% to about 30% titanium, in the range of about 20% to about 30% silicon, in the range of about 30% to about 40% boron, and in the range of 0% to about 15% carbon. Carbon, generally in the form of carbides, can be present if desired in the inner core, but since it is probably not present in the coating composition, at least in amounts which contribute properties, it is not considered material to the coating invention. The titanium and silicon can be provided by a suitable amount of a TiSi source, for example, in the range of about 50 to about 60% of a TiSi source such as TiSiFe in admixture with a source of boron and optional carbon, for example, B₄C in an amount of about 40 to about 50%.

The inner core may also contain additional materials. The additional materials may include: carbides, such as tungsten carbide, titanium carbide, vanadium carbide, and the like; oxides, such as aluminum oxide, zirconium oxide, and the like; and borides, such as nickel boride, iron boride, and the like. The inner core may also include additional metal powders, such as aluminum, nickel, or alloy powder, or composite powders, such as tungsten carbide nickel. As an example, the inner core can include in the range of about 0. 1 to about 10% molybdenum, about 0. 1 to about 10% tungsten, about 0.1 to about 10% neodymium, and about 0. 1 to about 10% carbon. Further, metal or metal alloy powders comprising magnesium, phosphorus, vanadium, manganese, iron, cobalt, nickel, copper, zirconium, niobium, molybdenum, tantalum and/or tungsten may be present in the inner core, for example, in the range of about 0. 1 to about 10%.

Additionally, the core components listed above can be alloyed into the sheath, and where this is done, the constituent need not be present in the inner core, or it can be present in a reduced amount. For example, titanium, silicon and boron can be alloyed in the sheath in the amount of about 2 to about 10% by weight, based on weight of the composite wire. In similar manner, the aluminum component may be present in the inner core, rather than the sheath.

The grain size of the powdered inner core will have an effect on the physical properties of the applied coating. Generally, the finer the grains of the powder, the more homogenous the coating will be and generally the better the wear and corrosion properties. However, acquisition costs and manufacturing constraints will limit the lower end of the grain size range. The cored wires may be formed in a conventional manner by placing the mix for forming the inner core, which need not be an agglomerated mix, onto the strip to be made into the outer metallic sheath. The strip can be drawn continuously through a plurality of wire drawing dies to form an outer wire sheath around an inner core.

The final outer diameter of the cored wire will depend upon the application for which it is used. For most applications, the cored wire final diameter ranges between about 0.8 mm and about 6.4 mm. Conventional cored wire manufacturing techniques are disclosed in U. S. Patent Nos. 6, 156,443 (Dallaire et al.) and 6,513 ,728 (Hughes et al.), both being hereby incorporated by reference.

In addition to the composite wires discussed above, a method of forming a wear resistant and corrosion resistant coating on a substrate is also provided. The method generally includes the steps of providing a composite wire having an outer sheath formed from a metal or alloy, and a powdered inner core, and coating a substrate by employing the composite wire in conjunction with thermal spraying techniques to form a fused metallic coating. The inventive wire is not weldable by commonly available techniques, so non-welding methods must be used to form the fused coating.

The resulting fused metallic chrome-free coating composition usually comprises, in bulk on a weight basis, about 60 to about 90% of base metal, at least about 2% aluminum, about 2 to about 10% titanium, about 2 to about 10% silicon, and about 2 to about 10% boron. The base metal is preferably selected from the group consisting of at least one of nickel, iron and cobalt, most preferably nickel. The coating can contain additional constituents if desired, for example, additional constituents selected from the group consisting of about 0. 1 to about

10% iron, about 0. 1 to about 10% molybdenum, about 0.1 to about 10% tungsten, and 0 to about 10% carbon.

The coatings according to the present invention are specifically designed for articles subjected to wear and/or corrosion. Such articles include, for example, boiler tubes, hydraulic piston rods, pump casings, rollers in the paper and steel industry, wear plates, journals and shafts, and turbine blades and casings.

In one application, the coatings are designed to protect boiler tubes against erosion-corrosion related wastage and are applied to the boiler tubes by means of a conventional arc spraying apparatus. However, it will be appreciated from the description below that the coatings could also be applied to the boiler tubes by other thermal spraying apparatus employing wires as the feed material. Arc spraying methods and apparatus are well documented in the art, see for example, U. S. Pat. Nos. 6, 156,443 (Dallaire, et al.); 5,837,326 (Dallaire, et al.); and European Patent No. EP 0 522 438 (Zurecki et al.) the disclosures of which are incorporated by reference.

EXAMPLE

A composite wire was formed according to the following composition.

16 wt % Core Material:

43 wt% B₄C (79 wt% B, 21 wt% C)

57 wt% TiSiFe (44 wt% Ti, 44 wt% Si, 10 wt% Fe, 2 wt% other)

Core composition (Elemental basis)

34 wt% B

9 wt % C

25 wt % Ti 25 wt% Si

6 wt% Fe

1 wt% other

84 wt% Sheath Material 95 wt% Ni 5 wt% Al

Composite Wire composition (Elemental basis)

79.8 wt% Ni 4. 1 wt% Si

4.1 wt% Al

1.2 wt% Fe 0.7 wt% C 6.1 wt% B 3.8 wt% Ti

Claims

1. A chromium-free metallic coating precursor comprising a composite of

at least about 54% by weight of at least one base metal selected the group consisting of iron, nickel, cobalt, lead, zinc, copper, tin, and aluminum, said coating precursor always comprising at least about 1% by weight of aluminum,

between about 1% and about 15% by weight of silicon, between about 1% and about 15% by weight of titanium, and between about 1% and about 15% by weight of boron.

2. A chromium-free coating precursor as in claim 1 comprising a composite of at least about 68% by weight of at least one base metal selected the group consisting of iron, nickel, cobalt, lead, zinc, copper, tin, and aluminum, said base metal always comprising at least about 2% by weight of alloyed aluminum and/or silicon,

between about 2% and about 10% by weight of silicon, between about 2% and about 10% by weight of titanium, and between about 2% and about 10% by weight of boron.

3. A chromium-free coating precursor as in claim 1 comprising a composite of at least about 76% by weight of at least one base metal selected the group consisting of iron, nickel, cobalt, and aluminum, said base metal always comprising at least about 3% by weight of alloyed aluminum,

between about 3% and about 7% by weight of silicon, between about 3% and about 7% by weight of titanium, and between about 3% and about 7% by weight of boron.

4. A chromium-free coating precursor as in claim 1 comprising a composite of an alloy of nickel, iron and/or cobalt with aluminum and a mass of silicon, titanium and boron-containing particles.

5. A fused chromium-free metallic coating composition comprising, in bulk on a weight basis, about 70% to about 90% by weight of at least one base metal selected the group consisting of iron, nickel, cobalt, lead, zinc, copper, tin, and aluminum, said metallic composition always comprising at least about 2% by weight of aluminum, about 2% to about 10% by weight of titanium, about 2% to about 10% by weight of silicon, and about 2% to about 10% by weight of boron.

6. A fused chromium-free metallic coating composition as in claim 5 comprising in the range of from about 2% to about 10% by weight of aluminum.

7. A fused chromium-free metallic coating composition as in claim 6 wherein the at least one base metal is selected from the group consisting of nickel, iron and cobalt.

8. A fused chromium-free metallic coating composition as in claim 7 wherein the base metal comprises nickel, said composition further comprising, in bulk on a weight basis, at least one additional constituent selected from the group consisting of about 0. 1 % to about 10% by weight of iron, about 0. 1% to about 10% by weight of molybdenum, and about 0. 1% to about 10% by weight of tungsten.

9. A composite wire containing essentially no chromium for producing a wear resistant and corrosion resistant coating on a substrate, said composite wire comprising a metallic outer sheath in the range of about 70 to about 95% by weight and an inner core of particles in the range of about 5 to about 30% by weight, wherein the metallic outer sheath comprises at least about 70 weight percent of a base metal and at least about 2 weight percent of alloyed aluminum and/or silicon, and wherein the inner core or particles comprises in the range of about 15% to about 30% by weight of titanium, in the range of about 15% to about 35% by weight of silicon, in the range of about 20% to about 50% by weight of boron, and in the range of 0% to about 15% by weight of carbon.

10. A composite wire as in claim 9, wherein the base metal comprises at least one of nickel, iron, and cobalt.

1 1. A composite wire as in claim 9 wherein the outer sheath comprises an alloy of nickel and aluminum and/or silicon.

12. A composite wire as in claim 9 wherein the outer sheath comprises in the range of about 85 to about 98 percent by weight of nickel and in the range of about 2 to about 15 percent by weight of alloyed aluminum and/or silicon.

13. A composite wire as in claim 12 wherein the outer sheath comprises in the range of about 90 to about 97 percent by weight of nickel and in the range of about 3 to about 10 percent by weight of alloyed aluminum.

14. A composite wire as in claim 9 wherein the inner core comprises in the range of about 20%- to about 30% by weight of titanium, in the range of about 20% to about 30% by weight of silicon, in the range of about 30% to about 40% by weight of boron, and in the range of 0% to about 15% by weight of carbon.

15. A composite wire as in claim 14 wherein the inner core comprises a mixture of in the range of about 50% to about 60% by weight of a TiSi source and in the range of about 40% to about 50% by weight of B₄C.

16. A composite wire as in claim 9 comprising a metallic outer sheath in the range of about 80 to about 90% by weight and an inner core in the range of about 10 to about 20% by weight.

17. A composite wire as in claim 9 further comprising in the range of about 0. 1% to about 10% by weight of molybdenum, about 0. 1% to about 10% by weight tungsten, and about 0.1% to about 10% by weight of carbon.

18. A method of forming a wear resistant and corrosion resistant coating on a substrate comprising the steps of: providing a composite wire according to claim 9 and employing the wire to form the coating.

19. A method as in claim 18, wherein the step of employing the wire to form the coating comprises thermally spraying the wire onto the substrate.