US3370006A

US3370006A - Bearings

Info

Publication number: US3370006A
Application number: US408366A
Authority: US
Inventors: Campbell Charles
Original assignee: Morganite Research and Development Ltd
Current assignee: Morganite Research and Development Ltd
Priority date: 1963-11-06
Filing date: 1964-11-02
Publication date: 1968-02-20
Anticipated expiration: 1985-02-20
Also published as: SE306901B; DE1300460B; GB1108354A

Description

United States Patent 3,370,006 BEARINGS Charles Campbell, Thames Ditton, England, assignor to Morganite Research and Development Limited, London, England, a corporation of England No Drawing. Filed Nov. 2, 1964, Ser. No. 408,366 Claims priority, application Great Britain, Nov. 6, 1963, 43,832/ 63 6 Claims. (Cl. 25212) This invention relates to an anti-friction composition, anti-friction elements made therefrom, and to bearings and bearing assemblies including such elements.

Applicants have developed the use of nickel oxide and/ or cobalt oxide in bearing surfaces in order to obtain excellent lubrication and wear resistance at high temperatures. It is found that these oxides form a patina on the bearing surface and it is believed that this patina provides the anti-friction properties.

It has 110W been found however that, for some reason which is not clear, the nickel or cobalt oxide are prone to an undue amount of wear below about600? C. vThis is a substantial disadvantage since, although the nickel or cobalt oxides are designed for use with high temperature engines and the like, such engines must pass through the lower temperature ranges during starting up; it is then that the nickel oxide or cobalt oxide, and hence the bearing, is liable to be subjected to excessive wear.

According to the present invention there is provided an anti-friction composition containing nickel oxide and/ or cobalt oxide together with a less wear-resistant, high melting (i.e. above 700 C.) solid lubricant which is nonreducing at high temperatures. The requirement that the solid lubricant must be non-reducing at high temperatures is set by the need to ensure that there is no extensive reduction of the nickel oxide or cobalt oxide during use.

The melting point of the solid lubricant must be above 700 C. and may have to be higher depending on'the use to which the anti-frictioncomposition is put. It will be clear that the melting point must always be higher than any temperature that the composition may reach during use.

Examples of solid lubricants that have been found effective include Group IIa fluorides, phosphates and borates, 6.g., Mg P O MgF Ca P O CaB40'1 and BaFz. Also found to be effective is lead monoxide. A particularly preferred solid lubricant is calcium fluoride which is found to operate as a lubricant at temperatures up to 900 C., and it is particularly efficient over the range 200-600 C. The solid lubricant is preferably used in amounts of at least 5% by weight of the anti-friction composition preferably 8-15% by weight of the composition. Suitably up to 25% by weight of the composition is present.

As stated above, the prime advantage of these solid lubricant additives lies in the provision of wear-resistant properties at temperatures below 600 C. They neverthe-v less also help in providing lubricating properties at higher temperatures.

Provided the anti-frictionelement is to be used in an oxidizing atmosphere, part of the cobalt or nickel oxides may be replaced by cobalt or nickel metal, which metal is then gradually oxidized in situ. There must, however, be sufiicient of these oxides present initially at the hearing surface to ensure that the element provides lubrication immediately on attaining the high temperatures, e.g.,

at least 30% of the bearing surface being the oxide. The oxidation in situ of the metal must be sufiicient to replace continuously the oxide patina as it is worn away.

It has'been'found desirable for some purposes to include in the antifriction composition oxides which form eutectic. mixtures with nickel and/or cobalt oxide. Examples of these are aluminium, magnesium, zinc and stannic oxides and titanium dioxide, and mixtures of these. The prime advantage in including these oxides is that they form a eutectic with all on some of the nickel oxide and/ or cobalt oxide, depending on the quantity added, and thus reduce the temperatures required for sintering or other coating processes.

To prepare a mix of the various components of the anti-friction composition, both ball milling and dry blending have been found suitable. The anti-friction composition may be formed into antifriction elements providing bearing surfaces. Thus the composition may be used to provide the bearing surfaces in a bearing assembly incorporating a plurality of elements bearing against one another.

Preparation of the anti-friction elements may be by any suitable method, the most preferred being by sintering or flame-spraying the aforesaid composition on to a suitable substrate. Other methods available include bonding of the composition on to the substrate in an enamel, as disclosed in our pending British patent application No. 9,745/63. The bearing surfaces may be applied directly'to the substrates, or an intermediate undercoat may be used as desired. 7

The substrates used for the bearings may be chosen to provide the optimum mechanical and other properties. 'So far as possible it should be arranged that the coefiicient of expansion of the substrate and that of the bearin surface are substantially the same. It has been found-that bearings using the anti-friction composition of the present invention work almost equally effectively over the entire temperature range 20 1000 C.

It is foreseen that bearing surfaces prepared from the anti-friction composition of the present invention will have many applications, among which may be mentioned the Cercor (honeycomb ceramic) heat exchanger (Cercor is a trademark) and rotary piston internal combustion engines of the Wankel type.

The invention illustrated in the following examples.

Example 1 A mix was prepared containing:

Green nickel oxide 900 Calcium fluoride The above quantities were weighed out and milled dry for 6 hours in a 10" diameter rubber lined ball mill at 60 rpm. with 1 kg. of l alumina cretoids.

The milled material was passed through a 100 mesh B.S. sieve and transferred to a Z bladed mixer. About 200 gm. ofan extrusion binder was then mixed in to produce an extrudable composition. The extrusion binder used-was that sold underthe trademark Cellofas. This, binds the particulate material together during shaping and handling, but decomposes during firing so that only the original components remain. I

Rods were extruded from the composition prepared as above, and sintered by firing to 1440 C. in an air atmosphere.

Coatings of the material were then applied to a stainless steel substrate with an undercoat of a nickel-chromium alloy by flame-spraying by the Rokide (trademark) process.

Bearings obtained by this method were used in a Cercor heat exchanger. At 600 C., 100 ft./min., lbs. load, wear rates of 0.00003 per hour were recorded.

Example 2 A mix was prepared containing:

. Gms. Green nickel oxide (200 RS. mesh) 750 Calcium fiouride (300 RS. mesh) 250 The powders were intimately mixed by dry blending, and then flame-sprayed on to a substrate prepared in the normal manner.

Instead of flamespraying the powders directly after mixing, they may be pressed into blocks and sintered at 1250 C. Following the sintering they are then crushed and sieved through 200 B5. mesh on to 300 B5. mesh, and subsequently frame-syrayed as above.

Examp'le3 A further mix was prepared containing:

. Gms. Green nickel oxide (200 RS. mesh) 950 Lead oxide (PbO) (300 ES. mesh) 50 The powders were mixed by dry blending and flamesprayed on to a substrate as in Example 2. In this case sintering was carried out at 1500 C.

Bearing surfaces prepared from this mix had good running properties over a wide range of temperatures. They were also found to have a smaller coeflicient of expansion than the mix of Example 2.

Example 4 The wear rate of bearings made according to this invention was measured by forming a /8" diameter pad of bearing material, and holding it in sliding contact with the underneath stellite-coated surface of a counterface rotating about a vertical axis. The wearrate was determined by observing the weight loss per hour of the bearing material, and converting this figure into the mean thickness of the material having the same weight as that lost. The tests were carried out with a predetermined pressure between the pad of bearing material and the counterface, i.e., a predetermined bearing load, and the apparatus was contained in a heated chamber. The re- 4 Examp'le6 Percent NiO 90 Mg P O Example 7 Percent CoO 85 PhD 15 Example8 Percent NiO 90 (2313 07 Example9 Percent C00 85 CaF What is claimed is:

1. A wear-resistant element comprising a composition flame-sprayed onto a substrate, said composition consisting essentially of at least one oxide selected from the group consisting of nickel oxide and cobalt oxide, together with a material selected from the group consisting of lead monoxide, and fluorides, phosphates and borates of Group Ila metals in an amount of from 5 to 25% by weight of the composition.

2. A wear-resistant element comprising a composition flame sprayed onto a substrate, said composition consisting essentially of at least one oxide selected from the group consisting of nickel oxide and cobalt oxide, together with a material selected from the group consisting of magnesium pyrophosphate, calcium pyrophosphate, calcium pyroborate, magnesium fluoride and barium fluoride in an amount of from 5 to 25% by weight of the composition.

3. A wear-resistant element comprising a composition flame-sprayed onto a substrate, said composition consisting essentially of at least one oxide selected from the group consisting of nickel oxide and cobalt oxide, together with calcium fluoride in an amount of from 5 to 25% by weight of the composition.

4. A wear-resistant element comprising a composition flame-sprayed onto a substrate, said composition consisting essentially of (1) at least one first oxide selected from sults of the experiments are tabulated below: the group consisting of nickel oxide and cobalt oxide,

TABLE 1 Test Temp, Bearing Surface Counter- Wear- Material N 0. C. load, speed, lace rate, 10-

p.s.i. It. p.111. inJhr.

NiO 400 25 A 0.3 Wt. NiO and 1 400 60 25 A 0. 49 35% Wt. CaFg. 2 400 60 25 B O. 45 90% wt. NiO and 1 400 60 25 A 0. 09 10% Wt. CaFz. 2 400 60 25 B 0. 06

Examples 5-9 ExampleS Percent NiO 50 C00 4O CaF 10 (2) a material selected from the group consisting of lead monoxide and fluorides, phosphates and borates of Group Ila metals in an amount of from 5 to 25% by weight of the composition, and (3 at least one second oxide selected from the group consisting of aluminum oxide, magnesium oxide, zinc oxide, stannic oxide and titanium dioxide, the first and second oxides being present in substantially-eutectic proportions.

5. A wear-resistant element comprising a composition flame-sprayed onto a substrate, said composition consisting essentially of (1) at least one oxide selected from the group consisting of nickel oxide and cobalt oxide in an amount of at least 30% by weight of the composition,

(2) at least one metal selected from the group consisting of nickel and cobalt in an amount ranging from a trace up to 65% by weight of the composition, and (3) a material selected from the group consisting of lead monoxide, and fluorides, phosphates and borates of Group IIa metals in an amount of from 5 to 25% by weight of the composition.

6. The wear-resistant element of claim 4 wherein said material is calcium fluoride.

6 References Cited UNITED STATES PATENTS 3,122,505 2/1964 Rulon-Miller et a1. 252-12 3,125,519 3/1964 Graue et a1 252-12 3,297,571 1/1967 Bonis 252-12 DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.

Claims

5. A WEAR-REAISTANT ELEMENT COMPRISING A COMPOSITION FLAME-SPRAYED ONTO A SUBSTRATE, SAID COMPOSITION CONSISTING ESSENTIALY OF (1) AT LEAST ONE OXIDE SELECTED FROM THE GROUP CONSISTING OF NICHEL OXIDE AND COBALT OXIDE IN AN AMOUNT OF AT LEAST 30% BY WEIGHT OF THE COMPOSITION, (2) AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL AND COBALT IN A AMOUNT RANGING FROM A TRACE UP TO 65% BY WEIGHT OF THE COMPOSITION, AND (3) A MATERIAL SELECTED FROM THE GROUP SONSISTING OF LEAD MONOXIDE, AND FLUORIDES, PHOSPHATES AND BORATES OF GROUP IIA METALS IN AN AMOUNT OF FROM 5 TO 25% BY WEGHT OF THE COMPOSITION.