Wear piece element and method of construction
View Patent ↗A method of construction of a tungsten carbide/TSP insert for hard facing a wear surface comprises the steps of forming a tungsten carbide body ( 12 ) in a mold. After the molding step, a channel section slot ( 24 ) or pocket ( 24 ′) is created in the body before it has hardened substantially. The body is then heat-treated to harden it. A TSP body ( 32 ) is fitted in the slot/pocket ( 24/24 ′) so that it is a close sliding fit between the sides ( 18 ) of the slot, and is of the same depth as the slot. The TSP is (preferably) brazed into the slot. The insert has pips ( 30 ) on its edges ( 18 ) to facilitate welding to a substrate prior to a final brazing step.
1. A method of hard-facing a substrate comprising:
constructing a tungsten carbide/ultra-hard insert by:
forming a tungsten carbide body with a slot or forming a tungsten carbide body with a pocket having a shape of an aperture;
fitting an ultra-hard body in said slot or pocket;
fixing the ultra-hard body therein by brazing said ultra-hard body in the slot or pocket of the tungsten carbide body using a first braze material; and
hard-facing said substrate with the insert by brazing said insert to the substrate, wherein the step of brazing said ultra-hard body in said slot or pocket is a separate and preceding step to a step of brazing said insert to the substrate.
2. A method as claimed in claim 1 , wherein said tungsten carbide is pressed into a solid body, said tungsten carbide is presintered, said slot is then cut in the body, and said body is then sintered.
3. A method as claimed in claim 2 , wherein said cut is made with a diamond grinding wheel to form the slot.
4. A method as claimed in claim 1 , wherein said ultra-hard body is TSP.
5. A method as claimed in claim 1 , wherein the slot or pocket is in a bottom face of the insert adapted to seat on a substrate and wherein edges of the slot or pocket on said bottom face are welded to the substrate for intermediate fixing of said insert between said brazing steps.
6. A method as claimed in claim 1 , wherein the step of brazing said ultra-hard body in said slot or pocket is performed in a furnace.
7. A method as claimed in claim 4 , wherein the TSP body is coated with a material that facilitates adhesion of a braze material.
8. A method as claimed in claim 7 , wherein the coating is selected from the group comprising titanium, tungsten, nickel and copper.
9. A method as claimed in claim 3 , wherein edges of the slot or pocket on said bottom face are adapted to be welded to the substrate for intermediate fixing of said insert and wherein two ridges are formed across the tungsten carbide body such that said slot cuts the ridges and leaves four pips, two on each edge of the slot, whereby said welding step is facilitated by concentrating electric discharge through said pips comprising the primary contact with the substrate.
10. A method as claimed in claim 1 , wherein the ultra-hard body is shielded by the tungsten carbide body from direct washing with flame in a flame-spray brazing step employed to braze the inserts to the substrate.
11. A method as claimed in claim 10 , in which the dimensions of the substrate are corrected after brazing of the inserts to the face of the substrate, said adjustment being effected by grinding the braze lying on the exposed faces of the insert and said exposed face, but without grinding the ultra-hard body.