US3472704A - Wear resistant member - Google Patents

Description

Oc 14,1969 R. D. WATSON ET AL 3,472,704

WEAR RESISTANT MEMBER Filed Sept. 21, 1966 gw Q Maw United States Patent U.S. Cl. 1483 11 Claims ABSTRACT OF THE DISCLOSURE The invention relates to the production of a material suitable for use as a bearing member which is wear resistant while operating in water at temperatures" up to about 600 F. The material comprises an alloy of zirconium and 0.05 to wt. percent titanium having an oxide coating thereon of a thickness of 1.4 10" inch to 5.5 10-' inch.

This invention relates to a method of producing a material having an improved wear-resistant surface.

Most materials now in use for bearings and rubbing surfaces operating in water at temperatures up .to 600 F. have inadequate wear and galling resistance.

In the past, numerous attempts have been made to improve the wearability of bearings and sliding surfaces by preoxidizing the specimens in air before using them. This has been attempted with various grades of stainless steel, Waukesha 88 alloy, pure zirconium, and tin plated stainless steel. Whenever an oxide layer was produced on the specimen its wear resistance improved considerably. Most of the oxide layers were difiicult to reproduce consistently, probably because the' oxidation characteristics were dependent on low level impurities in the material and these varied from batch to batch. Reactor grade zirconium and Waukesha 88 were two exceptions. Both these materials could be oxidized to produce consistently good oxide layers. They had, however, a decided dis----- advantage in that the oxide layer producible thereon was too thin to afford adequate wear protection for any length of time under hard rubbing contact.

It is an object of this invention to improve the wear and galling resistance of rubbing surfaces exposed to temperatures up to 600 F. and to provide more adequate erosion resistance in such surfaces when exposed to high velocity water.

The invention resides broadly in a method of producing a material having an improved wear-resistant surface which comprises forming an alloy consisting essentially of zirconium and 0.05 to 10 weight percent titanium, and heating said alloy in air at a temperature of 350 C. to 800 C. to form thereon an oxide coating of a thickness of 1.4x 10- inch to 5.5)(10 inch.

The invention also resides in a bearing member consisting essentially of a binary alloy of zirconium and 0.05 to 10 weight percent titanium, said alloy having an oxide coating thereon of a thickness of 1.4x 10 inch to 5.5 10 inch.

In the ensuing description, reference will be made to the accompanying drawings in which the single figure is an end elevation of a specimen wear testing device.

It has been found that the additions of relatively small amounts of titanium to zirconium to form a binary alloy is effective in producing an article on which an oxide layer can be produced, and that such an oxide coated ice article is satisfactory in achieving the objects of the invention.

In accordance with the invention, a binary alloy of zirconium with additions of from 0.05 to 10 weight percent titanium is employed as the body of the article on which the wear and corrosion resistant rubbing surface is to be provided.

The' article is heated in air to produce an oxide coating thereon having a thickness of about l.4 10- inch to 5.5 10- inch. An oxide layer of 1.4 10- inch is advisable for adequate effectiveness. Layers in excess of about 5 .5 X 10- inch have a tendency to spall.

An oxide layer of effective quality can be produced on the alloys mentioned at both high and comparatively low temperatures. Oxides produced at high temperatures are black in color while those produced at lower temperatures were off-white in color, the actual color varying with the titanium content. The temperature range for effective treatment is 350 C. to 800 C. However, close temperature control is necessary for production of uniformly satisfactory coatings.

For instance, an alloy of Zr 0.5 wt. percent Ti to Zr 10 wt. percent Ti may be oxidized at 375 C. to 400 C. until a weight gain of 0.5 g./dm. to 2.0 g./dm. has occurred, such weight gain corresponding to an oxide thickness of 1.4 10' inch to 5.5 10- inch. This treatment will produce a white oxide coating. The duration of this heat treatment will usually be about 12 to hours, preferably about 65 hours.

As another example of treatment, an alloy of Zr 0.05 wt. percent Ti to Zr 1 wt. percent Ti may be oxidized at 750 C. to 800 C. until a weight gain of 0.36 g./dm.? to 0.6 g./dm. (equal to an oxide thickness of 1X10 to 1.7 10- inch), or an alloy of Zr 5 wt. percent Ti to Zr 2 wt. percent Ti may be oxidized at 700 C. to produce this same range of weight gain. This will result in a black oxide' coating. In this example, the maximum coating thickness is desirably 2 10- inch. The duration of this treatment will usually be about 0.25 to 7 hours.

The following Table I sets forth, by way of example, particular oxidation conditions for specific alloys.

TABLE I Oxidation Conditions Oxidation Conditions for White Oxide for Black Oxide Tim Temp, Time, Temp hrs. C. hrs. C.

Zr 10 wt., percent Ti.-. 24 to 65 375 to 400 Zr 5 wt., percent Ti 2 to 65 375 to 400 O. 25 700 65 350 2 Zr 1 .24 to 48 375 to 400 0. 25 to 0. 50 800 24 to 65 400 1 to 2 800 Zr 0.5 wt., percent TL. 48 to 65 375 3 to 4 700 to 750 65 350 Zr 0.25 wt., percent Ti 3 to 5 800 Zr 0.10 Wt;., percent Ti 4 to 6 800 Zr 0.05 wt., percent Ti I 5 to 7 800 A number of specimens prepared in accordance with the invention were wear tested in comparison with a standard specimen. Zirconium oxidized at 800 C. for 2 hours in air was used as a standard since it was considered to be one of the best wear resistant materials available.

Two standard size specimens, indicated at 10 and 11- The specimens were rated according to the following formula:

Ratin Calculat-ed Oxide Thickness X g Depth of Wear Scar Test Duration (mins) This rating number is indicative of how long a specimen would run under the test conditions before the oxide layer was penetrated. A sample having a rating of on a 2 hour test would be expected to last hours.

The results of the wear tests with the 304 stainless steel journals are given in Table II.

TABLE II Weight Equivalent Length Maximum Gain of Oxide of Test, Depth of Rating Specimen, Thickness, min. Wear Scar, Number mgjdm. inJEiO; (0) 111x6 0;

inch square by 0.105 inch Oxidizing Conditions 400 White 400 do.. 375 ..do..

in the drawing, about 0.625

thick were oxidized under the same conditions and mounted in a specimen holder 12. The specimens were held firmly in place by clamping screws 13. A 304 stainless steel journal 14 0.750 inch diameter by 1 inch long was rotated in contact with the specimens at a speed of 77 rev./min. under a load of lbs. in demineralized pH 7 water at room temperature, conductivity about 2.0 mho. The Hertz stress at the beginning of the test was approximately 18,000 lb. f./in. and this decreased 10 as wear progressed. The condition of the oxidized specimens was checked at 10 minute intervals. The test was terminated after 2 hours running time or as soon as the 5 06350580835 25 4 38234526942M47 O00 flw0 0 0 O 0 0 LO 0 0 0 0 wmm wwwwmmwwwwmm 111%111111111111 02430811935458.0215 GVmQoamLZZZLZiLQLLZO ZLLLQQQLQQLQQQQQO 0 Emm tsnnnnem 0012110 01 A second series of tests were conducted using Waukesha 88 for the journals instead of 304 stainless steel, and under a load of 200 lbs. at a speed of 225 rev./min. The rest of the conditions were the same. The Hertz stress at the beginning of the tests was approximately 60,000 lb. f./in. The results of these tests are given in Table III.

TABLE 111' Oxidizing Equivalent Conditions Weight Oxide Length Depth of Gain of Thickness, of Test, Wear Scar,

' in.X10 min. in.X10 (Rating (A) (C) (B) Number 1 Pure Zr.

journal wore through the oxide layer. The test was repeated using specimens oxidized at different temperatures for different lengths of time.

When the specimens were mounted with the journal stopped, the load applied to each specimen was the same. When the journal was rotated the load on the right hand specimen was greater than the load on the left hand spec- 5286315748871 m7 6 6 fiw3 ZL1 0 0 0 0 0275568129885 G mLQmZLLZZZLQQ m m m tnttta O1020/\ A number of specimens prepared in accordance with the invention were also corrosion tested in water at 75 C. and 177 C. The water used was deionized steam con- 70 densate. The pH was adjusted by adding LiOH to the water and the tests at C. conducted at pH 7 and pH 10. The tests at 177 C. were made in a static autoclave at pH 10 only. The oxygen content of the water was kept below 0.1 p.p.m. After the tests the specimens were 75 reweighed to determine their weight loss or gain. The

l Pure Zr.

imen because the friction force tended to add to the load on the right hand side while subtracting from the load on the opposite side. Because of this increase in load, the wear scar on the right hand specimen during the test is larger than the scar formed on the opposing specimen.

Therefore, the results of all wear tests carried out were based on the right hand specimen because it had the greater wear and because the actual normal load applied to the specimen was not so dependent on the coefiicient of friction.

results are given in Table IV, which also includes corresponding wear ratings.

TABLE IV 6 a temperature of about 375 C. to 400 C. for 24 to 65 hours.

Wear Rating in pH 7 Oxidizing Corrosion Rate, mg./dn. month Water at Room Treatment Temperature Against Percent 75 C. 177 C. i in Time, Temp, Waukesha 304 Alloy hrs. 0. pH 7 pH 10 pH 7 pH 10 88 Stainless 10 65 400 3 4 -39 d -149 13. 5 13. 3 5 65 400 +15 7. 2 10. 6 10 65 375 e 3 6. 6 8. 7 5 24 400 +17 6. 8 2. 2 24 400 -7 6. 3 4. 2 10 24 400 +12 3. 1 3. 0 65 375 +6 2. 5 6. 0 0. 5 G5 375 +1 1. 7 5. 3 2 1.5 700 1 +1 0.8 7.8 0. 5 65 400 13 0.8 5. 3 0. 5 1. 5 800 a -2 0 1 2. 9 1. 0 65 400 +1 3. 7 0. 5 24 400 6 1 0. 1 1. 0 0. 5 800 e 1 0. 1

a Corrosion tested for one month.

b Corrosion tested for two months except where noted.

0 Weight gain=+; weight ss= 9 Most of the weight loss was due to a chip at one corner. Corrosion tested for six months.

It will be observed that the corrosion resistance of the specimens to 75 C. water is exceptionally good, the corrosion rates of most of the oxidized materials being less than 5 mg./dm. /mos.

We claim:

1. A method of improving the wear-resistant surfaces of a zirconium bearing member that operates in water at temperatures up to 600 F. which comprises adding 0.05 to 10 wt. percent titanium to zirconium to form a binary alloy consisting essentially of zirconium and 0.05 to 10 wt. percent titanium, forming said bearing member from said alloy, said member consisting essentially of said alloy, heating said member in air at a substantially constant temperature selected from the range 350 C. to 800 C. for a period 0.25 to 7 hours to produce an oxide coating on said member, and terminating said heating step when said oxide coating has a thickness within the range of 1.4 10 inch to 5.5 X l0 inch whereby the final thickness of said coating is within said range.

2. A method of producing a material having an improved wear-resistant surface as defined in claim 1, wherein said titanium content of said alloy is 0.5 to 10 weight percent.

3. A method of producing a material having an improved wear-resistant surface as defined in claim 1, wherein said titanium content of said alloy is 5 to 10 weight percent.

4. A method of producing a material having an improved wear-resistant surface as defined in claim 1, wherein said heating step is conducted at a temperature of 450 C. to 400 C. for 12 to 65 hours.

5. A method of producing a material having an improved wear-resistant surface as defined in claim 1, wherein said heating step is conducted at a temperature of 700 C. to 800 C. for 0.25 to 7 hours, and said coating has a maximum thickness of 2x10 inch.

6. A method of producing a material having an improved wear-resistant surface as defined in claim 1, wherein said titanium content of said alloy is about 10 weight percent, and wherein said heating step is conducted at 7. A method of producing a material having an improved wear-resistant surface as defined in claim 1, wherein said titanium content of said alloy is about 5 weight percent, and wherein said heating step is conducted at a temperature of about 375 C. to 400 C. for 24 to 65 hours.

8. A bearing member for operation in water at temperatures up to 600 F. consisting essentially of zirconium and 0.05 to 10 wt. percent titanium, said member having on its surfaces an oxide coating of a thickness within the range of 1.4 10 inch to 5.5 10- inch.

9. A bearing member as defined in claim 8, wherein the titanium content of said alloy is about 5 to 10 weight percent.

10. A hearing member as defined in claim 8, wherein the titanium content of said alloy is about 5 weight percent.

11. A hearing member as defined in claim 8, wherein the titanium content of said alloy is about 10 weight percent.

References Cited UNITED STATES PATENTS 2,9T26,981 3/1960 Stout et a1. -177 X 2,987,352 6/1961 Watson 308241 FOREIGN PATENTS 555,952 4/ 1958 Canada.

' OTHER REFERENCES Bureau of Mines, Report 4658, A Preliminary Survey of Zirconium Alloys, Anderson et al., March 1950, pp. 40-42.

ANL-5229, Misch, Argonne Nat. Lab., December 1953, pp. 74 and 75.

CHARLES N. LOVELL, Primary Examiner U.S. Cl. X.R.

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