Hard-faced surface and a wear piece element
A hard faced surface comprises a metal substrate. Inserts are attached to the substrate as a covering layer on the substrate. Each insert comprises a thermally stable polycrystalline diamond (TSP) body (or polycrystalline diamond or cubic boron nitride) having a plan section, a contact surface and a flat top surface. A boundary coating on the ultra-hard body renders the body wettable by first braze material. A tungsten carbide cap is brazed with said first braze material to at least the top surface of the TSP block. The inserts are brazed to the substrate in a closely packed side-by-side formation with a second braze material that penetrates the gaps between the inserts and between the contact surface of the bodies and the metal substrate. The tungsten carbide caps of the inserts provide a gauge for the hard faced surface, which caps are ground in a finishing step exposing the caps and providing the hard faced surface with a desired dimension including an amount of the thickness of the caps.
1. A hard faced surface comprising:
a) a metal substrate,
b) inserts comprising:
i) an ultra-hard body in a geometric shape having a plan section enabling a plurality of the bodies to be tiled over a surface without substantial gaps between them, a contact surface and a flat top surface;
ii) a boundary coating of tungsten on the ultra-hard body to render the body wettable by braze material, wherein the tungsten reacts with carbon or nitrogen across the surface boundary of the body to form a tungsten carbide or tungsten nitride interface between the boundary coating and the body; and
iii) a tungsten carbide cap brazed to at least the top surface of the ultra-hard body with a first braze material;
c) the inserts are attached at the contact surface to the substrate as a covering layer on the substrate, wherein
d) the inserts are brazed to the substrate in a side by side formation with a second braze material that penetrates the gaps between the inserts and between the contact surface of the bodies and the metal substrate, the tungsten carbide caps of the inserts providing a gauge for the hard faced surface that is ground in a finishing step, which finishing step serving to expose the caps and to remove at least a portion of the depth of the caps.
2. The hard faced surface of claim 1 , in which pips are disposed on the contact surface of the bodies to facilitate tack-welding of the inserts to the substrate.
3. The hard faced surface of claim 1 , in which said plan section is rectangular and said side by side formation is a closely packed tile formation, whereby the ultra-hard body is shielded from direct washing with flame in a flame-spray brazing step employed to braze the inserts to the substrate.
4. The hard faced surface of claim 3 , in which side walls of the ultra-hard bodies are separated from each other in said formation only by said second braze material.
5. The hard faced surface of claim 3 , wherein the inserts are arranged in a plurality of rows, each row comprising a plurality of inserts disposed in an end-to-end arrangement.
6. The hard faced surface of claim 5 , wherein the inserts in adjacent rows are offset by a distance approximately equal to half the length of the inserts.
7. The hard faced surface of claim 3 , wherein the inserts are tiled on the substrate in a chevron or herring-bone pattern of overlapping inserts.
8. The hard-faced surface of claim 3 , wherein at least 50% of the surface area of said metal substrate is covered by said inserts, the remaining area comprising space between the inserts filled with the second braze.
9. The hard-faced surface of claim 3 , wherein at least 60% of the surface area of said metal substrate is covered by said inserts, the remaining area comprising space between the inserts filled with the second braze.
10. The hard-faced surface of claim 1 , wherein the second braze material is different from the first braze material.
11. The hard-faced surface of claim 1 , wherein the metal substrate is the outer surface of a drill string stabiliser.
12. The hard faced surface of claim 1 , wherein said ultra-hard body is thermally stable polycrystalline diamond.
13. The hard faced surface of claim 1 , wherein the boundary coating comprises tungsten alloyed with fluorine.
14. The hard faced surface of claim 1 , wherein the boundary coating comprises a first coating that is between 0.1 and 25 microns thick.
15. The hard faced surface of claim 14 , wherein the boundary coating further comprising a second coating applied to the ultra-hard body, wherein the second coating comprise tungsten between 5 and 30 microns thick, and wherein the first coating is less than 5 microns thick.
16. The hard faced surface of claim 1 , wherein the tungsten carbide cap is between 0.2 and 1 mm thick.
17. The hard faced surface of claim 1 , wherein said first braze material is a copper-based braze material.
18. The hard faced surface of claim 1 , wherein the ultra-hard body is substantially cuboidal in shape, whereby the plan section of ultra-hard body is substantially rectangular.
19. The hard faced surface of claim 18 , wherein the plan section of the tungsten carbide cap is substantially the same as the plan section of the ultra-hard body.
20. The hard faced surface of claim 19 , wherein the plan section of the tungsten carbide cap has at least one rounded corner.
21. The hard faced surface of claim 1 , further comprising at least one pip on a bottom surface of the ultra-hard body, which pip facilitates tack-welding of the insert onto the substrate.
22. The hard faced surface of claim 21 , wherein the pip comprises a separate element brazed onto the contact surface.
23. The hard faced surface of claim 22 , wherein the ultra-hard body is formed with a groove in which to receive said element.