Apparatus and method for cooling a hard metal applied to the surface of a metal alloy substrate

1. An apparatus for cooling a hard metal applied in a molten or semi-molten state to the surface of a workpiece, the apparatus comprising:

a chill block formed of a heat-conducting material,

a contact surface provided on the chill block for contacting the hard metal applied on the surface of the workpiece for cooling the hard metal,

a coolant passage in the chill block for conducting a cryogenic coolant through the chill block to cool the chill block, and

at least one ejector port in the chill block in communication with the coolant passage for ejecting cryogenic coolant from the chill block onto the hard metal for further cooling the hard metal,

wherein the chill block includes a protrusion on which the contact surface is formed, the protrusion extending below the coolant passage and the contact surface being positioned below the at least one ejector port.

2. The apparatus according to claim 1 , wherein the heat conducting material of the chill block comprises copper.

3. The apparatus according to claim 1 , wherein at least the contact surface has a width equal to or greater than a width of the hard metal to be cooled that is applied on the surface of the workpiece.

4. The apparatus according to claim 1 , wherein the at least one ejector port is located on one side of the protrusion and wherein an application of hard metal on the metal substrate is configured to take place on an opposite side of the protrusion such that the hard metal is shielded from cryogenic coolant ejected from the at least one ejector port during hard metal cooling.

5. The apparatus according to claim 1 , wherein the contact surface is rounded or chamfered at least in part in a direction permitting relative movement of the contact surface and the surface of the hard metal being cooled.

6. The apparatus according to claim 1 , wherein a plurality of ejector ports are provided for ejecting cryogenic coolant from the chill block onto the hard metal.

7. The apparatus according to claim 1 , wherein a plurality of ejectors ports are spaced from one another in a lateral direction across a width of the chill block and the hard metal being cooled.

8. The apparatus according to claim 1 , wherein a plurality of ejector ports are spaced from one another in a longitudinal direction along a depth or length of the chill block and the hard metal being cooled.

9. A method for cooling a hard metal applied on a surface of a workpiece comprising:

applying a molten or semi-molten hard metal on a surface of a workpiece,

rapidly cooling the hard metal applied on the workpiece utilizing the apparatus of claim 1 ,

wherein a cryogenic coolant is conducted through the coolant passage in the chill block while the contact surface of the chill block is in contact with the hard metal and cryogenic coolant is ejected from the at least one ejector port in the chill block onto the hard metal,

wherein the molten or semi-molten hard metal is applied under protection of a shielding gas, and wherein the cryogenic coolant is ejected from the at least one ejector port of the chill block on a side of the contact surface opposite a side of the contact surface adjacent the gas-shielded application of the hard metal, the protrusion of the chill block serving as a shield to prevent the cryogenic coolant from mixing with the shielding gas.

10. The method according to claim 9 , wherein the hard metal is applied to the surface of the workpiece by an arc welding process.

11. The method according to claim 9 , wherein the contact surface of the chill block is contacted with the hard metal immediately after the hard metal is applied while the hard metal is still at least partially molten or semi-molten.

12. The method according to claim 9 , wherein the surface of the workpiece to which the hard metal is to be applied is formed on an alloy steel.

13. The method according to claim 12 , wherein the hard metal applied comprises an amorphous metal alloy.

14. The method according to claim 9 , wherein the hard metal is progressively applied on the surface of the workpiece and the hard metal applied rapidly cooled by relatively moving the chill block and the workpiece with the contact surface of the chill block in contact with the hard metal as it is applied.

15. The method according to claim 9 , wherein the cryogenic coolant is liquid nitrogen.

16. The method according to claim 9 , including applying the contact surface on the hard metal while the hard metal is still at least partially molten or semi-molten to smooth and rapidly cool the hard metal.

17. A method of improving the application of hard metal to the surface of an alloy steel substrate comprising:

preheating the alloy steel substrate to a temperature within the range of 300 to 600 degrees Fahrenheit,

applying the hard metal to the surface of the preheated alloy steel substrate as a weld bead applied by an arc welding process,

rapidly cooling the weld bead utilizing a chill block in contact with the weld bead, wherein the utilizing the chill block comprises conducting a cryogenic coolant through a coolant passage in the chill block and ejecting the cryogenic coolant from an ejector port in the chill block across the width of the weld bead.

18. The method according to claim 17 , wherein the steps of applying the hard metal and rapidly cooling the weld bead are performed progressively along the surface of the alloy steel substrate with relative movement of the chill block along the weld bead as the weld bead is applied by the arc welding process.

19. The method according to claim 17 , wherein the weld bead is a wide weaved bead.

20. The method according to claim 17 , wherein the weld bead is a stringer bead.