RHODIUM ALLOYS

Abstract

Disclosed is an electrode including a rhodium alloy, wherein the rhodium alloy includes rhodium and nickel. The alloy includes a greater quantity of rhodium as compared to any other individual element of the alloy.

Claims

1-18. (canceled)

19. An electrode comprising a rhodium alloy, wherein the rhodium alloy comprises: i) rhodium; and ii) 5 to 45 wt % of nickel; wherein the alloy comprises a greater quantity of rhodium as compared to any other individual element of the alloy.

20. An electrode according to claim 19, wherein the rhodium alloy further comprises: iii) one or more elements selected from the group consisting of yttrium, zirconium and samarium.

21. An electrode according to claim 19, wherein the rhodium alloy comprises: a) about 50 wt % or more of rhodium; b) up to about 49.99 wt % each of any one or more elements selected from the group consisting of iridium, platinum and palladium; c) up to about 35 wt % of ruthenium; d) about 0.01 to about 49.99 wt % of nickel; e) up to about 5 wt % each of any one of more elements selected from the group consisting of niobium, tantalum, titanium, chromium, molybdenum, cobalt, rhenium, vanadium, aluminium, hafnium and tungsten; and wherein the total wt % of the rhodium alloy adds up to 100 wt %.

22. An electrode according to claim 19, wherein the rhodium alloy comprises: a) about 75 wt % or more of rhodium; b) 0 wt % each of any one or more elements selected from the group consisting of iridium, platinum and palladium; c) 0 wt % of ruthenium; d) about 0.01 to about 25 wt % of nickel; e) up to about 5 wt % each of any one of more elements selected from the group consisting of niobium, tantalum, titanium, chromium, molybdenum, cobalt, rhenium, vanadium, aluminium, hafnium and tungsten; and wherein the total wt % of the rhodium alloy adds up to 100 wt %.

23. An electrode according to claim 19, wherein the rhodium alloy comprises: a) about 50 to about 95 wt % or more of rhodium; b) up to about 25 wt % each of any one or more elements selected from the group consisting of iridium, platinum and palladium; c) up to about 35 wt % of ruthenium; d) about 0.01 to about 49.99 wt % of nickel; e) up to about 5 wt % each of any one of more elements selected from the group consisting of niobium, tantalum, titanium, chromium, molybdenum, cobalt, rhenium, vanadium, aluminium, hafnium and tungsten; and wherein the rhodium alloy comprises at least one of iridium, platinum, palladium or ruthenium; and wherein the total wt % of the rhodium alloy adds up to 100 wt %.

24. An electrode according to claim 19, wherein the rhodium alloy is selected from the group consisting of: TABLE-US-00004 Rh Ir Ru Ni Mo Cr Ti Al W Zr Y Alloy (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) A 80 0 0 19.86 0 0 0 0 0.1 0.04 0 B 55 2.86 0 42 0 0 0 0 0.1 0.04 0 C 74 0.86 0 25 0 0 0 0 0.1 0.04 0 D 75 1.86 7.5 15.5 0 0 0 0 0.1 0.04 0 E 65 9.86 0 25 0 0 0 0 0.1 0.04 0 F 50 0 19.86 30 0 0 0 0 0.1 0.04 0 G 60 0 29.86 10 0 0 0 0 0.1 0.04 0 H 72.4 0 0 20 2.5 5 0 0 0 0 0.1 I 75 20 0 5 0 0 0 0 0 0 0 J 50 5 0 45 0 0 0 0 0 0 0 K 57.5 12.5 0 30 0 0 0 0 0 0 0 L 54.5 3 0 41.5 0 0 1 0 0 0 0 M 55 3 0 42 0 0 0 0 0 0 0 N 63.1 0 0 30.5 0 3.4 0 3 0 0 0

25. A spark plug comprising an electrode according to claim 19.

26. A rhodium alloy comprising: i) rhodium; ii) nickel; and iii) one or more elements selected from the group consisting of yttrium, zirconium and samarium; wherein the alloy comprises a greater quantity of rhodium as compared to any other individual element of the alloy.

27. A rhodium alloy according to claim 31, wherein the alloy comprises about 5 to about 45 wt % of nickel.

28. A rhodium alloy according to claim 31, wherein the alloy comprises: a) about 50 wt % or more of rhodium; b) up to about 49.99 wt % each of any one or more elements selected from the group consisting of iridium, platinum and palladium; c) up to about 35 wt % of ruthenium; d) about 0.01 to about 49.99 wt % of nickel; e) up to about 5 wt % each of any one of more elements selected from the group consisting of niobium, tantalum, titanium, chromium, molybdenum, cobalt, rhenium, vanadium, aluminium, hafnium and tungsten; and f) about 0.01 to about 1.00 wt % each of any one or more elements selected from the group consisting of yttrium, zirconium and samarium; and wherein the total wt % of the rhodium alloy adds up to 100 wt %.17. A rhodium alloy according to claim 31 the alloy comprises: a) about 75 wt % or more of rhodium; b) 0 wt % each of any one or more elements selected from the group consisting of iridium, platinum and palladium; c) 0 wt % of ruthenium; d) about 0.01 to about 25 wt % of nickel; e) up to about 5 wt % each of any one of more elements selected from the group consisting of niobium, tantalum, titanium, chromium, molybdenum, cobalt, rhenium, vanadium, aluminium, hafnium and tungsten; and f) about 0.01 to about 1.00 wt % each of any one or more elements selected from the group consisting of yttrium, zirconium and samarium; and wherein the total wt % of the rhodium alloy adds up to 100 wt %.

29. A rhodium alloy according to claim 31, wherein the alloy comprises: a) about 50 to about 95 wt % or more of rhodium; b) up to about 25 wt % each of any one or more elements selected from the group consisting of iridium, platinum and palladium; c) up to about 35 wt % of ruthenium; d) about 0.01 to about 49.99 wt % of nickel; e) up to about 5 wt % each of any one of more elements selected from the group consisting of niobium, tantalum, titanium, chromium, molybdenum, cobalt, rhenium, vanadium, aluminium, hafnium and tungsten; and f) about 0.01 to about 0.50 wt % each of any one or more elements selected from the group consisting of yttrium, zirconium and samarium; wherein the rhodium alloy comprises at least one of iridium, platinum, palladium or ruthenium; and wherein the total wt % of the rhodium alloy adds up to 100 wt %.

30. A rhodium alloy according to claim 31, wherein the alloy is selected from the group consisting of: TABLE-US-00005 Rh Ir Ru Ni Mo Cr Ti Al W Zr Y Alloy (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) A 80 0 0 19.86 0 0 0 0 0.1 0.04 0 B 55 2.86 0 42 0 0 0 0 0.1 0.04 0 C 74 0.86 0 25 0 0 0 0 0.1 0.04 0 D 75 1.86 7.5 15.5 0 0 0 0 0.1 0.04 0 E 65 9.86 0 25 0 0 0 0 0.1 0.04 0 F 50 0 19.86 30 0 0 0 0 0.1 0.04 0 G 60 0 29.86 10 0 0 0 0 0.1 0.04 0 H 72.4 0 0 20 2.5 5 0 0 0 0 0.1 I 75 20 0 5 0 0 0 0 0 0 0 J 50 5 0 45 0 0 0 0 0 0 0 K 57.5 12.5 0 30 0 0 0 0 0 0 0 L 54.5 3 0 41.5 0 0 1 0 0 0 0 M 55 3 0 42 0 0 0 0 0 0 0 N 63.1 0 0 30.5 0 3.4 0 3 0 0 0

31. The electrode of claim 21, wherein the rhodium alloy further comprises about 0.01 to about 1.00 wt % each of any one or more elements selected from the group consisting of yttrium, zirconium and samarium.

32. The electrode of claim 22, wherein the rhodium alloy further comprises about 0.01 to about 1.00 wt % each of any one or more elements selected from the group consisting of yttrium, zirconium and samarium.

33. The electrode of claim 23, wherein the rhodium alloy further comprises about 0.01 to about 0.50 wt % each of any one or more elements selected from the group consisting of yttrium, zirconium and samarium.

34. A spark plug comprising an electrode according to claim 20.

35. A spark plug comprising an electrode according to claim 21.

36. A spark plug comprising an electrode according to claim 22.

37. A spark plug comprising an electrode according to claim 23.

38. A spark plug comprising an electrode according to claim 24.

Description

[0088] The invention will now be described by way of the following non-limiting Examples and with reference to the following figures in which:

[0089] FIG. 1 illustrates a cross-section through a wire of a rhodium ally (Alloy B) as manufactured.

[0090] FIG. 2 illustrates a rhodium alloy (Alloy B) which has been annealed at 1100° C. for 15 minutes and then compressed in a die.

EXAMPLES

Example 1

Alloy Preparation

[0091] The rhodium alloys detailed in Table 1 below are prepared by argon arc melting. All values are given in weight percent (wt %) based on the total weight of the alloy.

TABLE-US-00002 TABLE 1 Rh Ir Ru Ni Mo Cr Ti Al W Zr Y Alloy (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) A 80 0 0 19.86 0 0 0 0 0.1 0.04 0 B 55 2.86 0 42 0 0 0 0 0.1 0.04 0 C 74 0.86 0 25 0 0 0 0 0.1 0.04 0 D 75 1.86 7.5 15.5 0 0 0 0 0.1 0.04 0 E 65 9.86 0 25 0 0 0 0 0.1 0.04 0 F 50 0 19.86 30 0 0 0 0 0.1 0.04 0 G 60 0 29.86 10 0 0 0 0 0.1 0.04 0 H 72.4 0 0 20 2.5 5 0 0 0 0 0.1 I 75 20 0 5 0 0 0 0 0 0 0 J 50 5 0 45 0 0 0 0 0 0 0 K 57.5 12.5 0 30 0 0 0 0 0 0 0 L 54.5 3 0 41.5 0 0 1 0 0 0 0 M 55 3 0 42 0 0 0 0 0 0 0 N 63.1 0 0 30.5 0 3.4 0 3 0 0 0

[0092] Each alloy is subsequently processed to produce wire having a 1 mm or 2 mm diameter.

Example 2

Formability Testing

[0093] 1. Wire at 1-2 mm diameter of Alloy B is cut into 50 mm lengths; actual diameter is noted. FIG. 1 illustrates a cross-section through the wire. [0094] 2. Wire samples are evaluated in the as-drawn and annealed condition to check whether formability is condition dependent. The wire samples are annealed at 1100° C. in air for 15 minutes. [0095] 3. Evaluation uses a bespoke die set encompassing rectangular cavities held in a fly press. [0096] 4. The wire samples are placed in the appropriate cavity and the press closed to force the sample into the cavity. The press is manually operated. [0097] 5. Following pressing the wire samples are examined visually, by microscope and ultimately by cross sectioning and metallographic preparation to allow measurement, determine the degree of deformation and check whether the integrity of the samples are preserved. [0098] 6. Assessment of the alloy's formability is based on the presence of any cracks, the relative size (length/width) of the cracks and the degree of deformation as calculated by the relative thickness of the deformed wire in comparison to the original diameter.

[0099] FIGS. 1 and 2 illustrate that the alloy demonstrates a high degree of deformability and remains substantially crack free.

Example 3

Electrode Studies

[0100] The rhodium alloys of the present invention, an iridium standard and a rhodium standard are cut into electrode wire having 1 mm diameter. The wires are fixed into a four station test cell together with matching 3 mm diameter Ir earth electrodes and the gap between them adjusted and set with a vernier calliper. The test electrodes are set at negative polarity and the earth electrode as positive to concentrate erosion on the appropriate electrodes.

[0101] Testing commences with a 10 kV electric pulse driven by an automotive ignition coil being applied to each pair of electrodes at 200 Hz. This initiates a continuous series of rapid spark discharges between the electrodes as generated in a typical automotive engine. The test cell is visually checked at intervals to confirm functionality and after approximately 250 hr. the discharge is stopped and the electrode gap re-measured. A counter initiated at test commencement is used to measure elapsed time from which the number of spark discharges can be calculated.

[0102] The electrodes are reset in the test cell and discharge re-initiated. After a further approximately 250 hr. (approx. 500 hrs discharge time in total) the test is stopped and the same procedure of gap measurement and electrode inspection completed.

[0103] Test Duration

[0104] The test duration and approximate number of sparks were calculated. Therefore, for a 20 day test: [0105] 20 days×24 hrs/day=480 hrs [0106] 480 hrs×3600 seconds/hr=1,728,000 seconds [0107] 1,728,000 seconds×200 sparks/second=345,600,000 sparks (per test point)

[0108] Measurements of Gaps

TABLE-US-00003 Test gap - Startpoint Midpoint negative Gap Gap Endpoint Gap Gap Growth electrode (mm) (mm) (mm) (mm) 100% Ir 8.2 8.6 8.9 0.7 (comparative) 100% Rh 8.1 8.2 8.4 0.3 (comparative) Alloy A 8.1 8.2 8.3 0.2 Alloy B 8.1 8.1 8.2 0.1 Alloy H 8.1 8.0 8.3 0.2 Alloy I 7.9 7.9 8.0 0.1 Alloy J 8.0 8.1 8.2 0.2 Alloy K 8.0 8.1 8.2 0.2 Alloy L 8.0 8.1 8.2 0.3 Alloy M 7.9 8.1 8.2 0.3

[0109] The 100% Ir electrode exhibits the worst (most) erosion, the gap measurement changing by 0.7 mm+/−0.1 mm over the test duration.

[0110] The 100% Rh, and Alloy A, B and H-M electrodes exhibit less erosion than the 100% Ir electrode. The Alloy L and M electrodes exhibit comparable erosion resistance to the 100% Rh electrode over the test duration. The Alloy A, H, J and K electrodes exhibit better erosion resistance than the 100% Rh electrode as the gap measurements change by 0.2 mm+/−0.1 mm in comparison to 0.3 mm+/−0.1 mm for the 100% rhodium electrode over the test duration. Alloys B and I also exhibit better erosion resistance than the 100% Rh electrode as the gap measurements change by 0.1 mm+/−0.1 mm in comparison to 0.3 mm+/−0.1 mm for the 100% rhodium electrode over the test duration.