TITANIUM DIBORIDE COATED REFRACTORY METAL COMPONENT

Abstract

A component formed of a refractory metal has a surface that is at least partially coated with a layer of titanium diboride. There is also described a method of manufacturing the component and the application of TiB.sub.2 as a release agent in high-temperature applications.

Claims

1-11. (canceled)

12. A component consisting of a refractory metal and having a surface at least partially coated with a layer of titanium diboride.

13. The component according to claim 12, wherein said refractory metal is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, and alloys of said metals.

14. The component according to claim 12, wherein said refractory metal consists of at least 70% by weight of molybdenum.

15. The component according to claim 12, comprising a component body formed as a screw, a nut, a pin, a dowel pin, a washer, a bolt, a sheet, a clamp, a tube, a rod, or a U-shaped rail.

16. The component according to claim 12, being an assembly of welded and/or riveted individual parts.

17. The component according to claim 12, wherein the layer of TiB.sub.2 has a layer thickness in a range from 1 ?m to 5 ?m.

18. The component according to claim 12, wherein the surface of the component is completely coated.

19. The component according to claim 12, wherein the surface of the component is only partially coated.

20. The component according to claim 12, wherein said layer is a TiB.sub.2 layer deposited by chemical vapor deposition.

21. A component for high-temperature application, comprising a layer of titanium diboride forming a separating agent on the component for the high-temperature application.

22. A method of manufacturing a coated component, the method comprising the following steps: providing a component consisting of a refractory metal; and depositing a layer of titanium diboride on at least a portion of a surface of the component by chemical vapor deposition or by physical vapor deposition.

Description

EXAMPLES

[0029] TZM plate (molybdenum with weight fraction of 0.5 Ti and 0.08 Zr and 0.01 to 0.04 C) 140?80?9 mm, 9 mm deep through bore M6 thread milled.

[0030] Molybdenum washer: 18?6, 4?1.5 mm

[0031] Molybdenum screw: M6?12 mm

[0032] Comparison example 1 (C1): Molybdenum screws (rolled) without coating.

[0033] Comparison example 2 (C2): Several molybdenum screws (rolled) with a TiN CVD coating were fabricated using H.sub.2, N.sub.2 and TiCl.sub.4 at a temperature of 850? C. for 7 h. The TiN coatings were deposited on the surface of the screws. The thickness of the TiN coatings was 2.6 ?m to 3.1 ?m.

[0034] Example (E) according to the invention: several molybdenum screws (rolled) with a TiB.sub.2 CVD coating were prepared using H.sub.2, N.sub.2, TiCl.sub.4, and BCl.sub.3 at a temperature of 850? C. for 7 h. The thickness of the TiB.sub.2 coatings ranged from 2.6 ?m to 3.1 ?m.

[0035] As indicated in the table below, several tests were conducted to evaluate the TiB.sub.2 layer compared with the TiN layer and the uncoated component under different conditions. For this purpose, three screws (S1 to S3) with washers were selected in each case and screwed into the plate at a tightening torque of 12 Nm. High temperature treatments were performed at temperatures (T in ? C.) from 400? C. to 1800? C. and different atmospheres (A) (hydrogen (H), vacuum 10.sup.?6 mbar (V)) for different holding times (H). The opening torque (L in Nm) after the high temperature treatment was measured and the threads were visually inspected for seizing (S) and, if applicable, breakage (B) of the screw was detected.

TABLE-US-00001 S1 S2 S3 total Ex. T H A L S B L S B L S B S B E1 400 2 V 5 no no 5 no no 5 no no no no 1000 2 V 5 no no 5 no no 5 no no no no 1400 2 V 5 no no 5 no no 5 no no no no 1400 168 V 10 no no 10 no no 10 no no no no 1800 2 V 15 no no 15 no no 15 no no no no 1400 2 H 5 no no 5 no no 5 no no no no 1800 2 H 15 no no 15 no no 12 no no no no C1 400 2 V 15 no no 20 yes no 15 yes no partly no 1000 2 V 15 yes no 12 yes no 12 yes no yes no 1400 2 V 15 yes no 15 yes ja 15 yes yes yes partly 1400 2 H 12 yes yes 12 yes no 12 yes no yes partly C2 1400 2 V 5 no no 10 yes no 5 yes no partly no 1400 168 V 12 yes no 12 yes no 15 no no partly no 1800 2 V 10 yes no 10 yes no 10 yes no yes no 1400 2 H 10 yes no 5 no no 10 no no partly no 1800 2 H 12 yes no 12 yes no 10 yes no yes no

[0036] As can be seen from the above table, the uncoated components, in this case the plate and screw, show seizing already at low temperatures from 400? C. and are therefore unsuitable for high-temperature applications.

[0037] The TiN-coated screws show partial seizing of the components at 1400? C. in hydrogen atmosphere and in vacuum, also in long-term tests, and seizing of all components at 1800? C. in all atmospheres.

[0038] In contrast, the TiB2 coating according to the invention does not cause any seizing of the screw connection. Consequently, the coating can achieve the detachability of contacting refractory metal components even in long-term high-temperature applications. Cross-contamination between the components was not observed.