Controlled process for the production of a spray of atomized metal droplets

• US 5,176,874 A
• Filed: 11/05/1991
• Issued: 01/05/1993
• Est. Priority Date: 11/05/1991
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Mourer, David P., Christensen, Roy W.
• Primary Examiner(s): Roy, Upendra
• Application Number:
  US07/788,012
• Time in Patent Office: 427 Days
• Field of Search: 266/80, 266/92, 266/94, 266/202, 75/338, 75/339, 164/155
• US Class Current: 266/80
• CPC Class Codes: B05B 12/12 responsive to conditions of ambient medium or target, e.g. humidity, temperature position or movement of the target relative to the spray apparatus B05B12/082, B05B12/084 take precedence
• CPC Class Codes: B05B 7/1606 the spraying of the material involving the use of an atomising fluid, e.g. air B05B7/168, B05B7/1686, B05B7/20, B05B7/22 take precedence
• CPC Class Codes: C23C 4/123 Spraying molten metal

Abstract

A process and apparatus for producing a spray of atomized metal droplets includes providing an apparatus that forms a spray of molten metal droplets, the apparatus including a metal source and a metal stream atomizer, producing a stream of liquid metal from the metal source, and atomizing the stream of liquid metal with the metal stream atomizer to form the spray of molten metal droplets. A controlled spray of atomized metal droplets is achieved by selectively varying the temperature of the droplets in the spray of molten metal droplets, the step of selectively varying including the step of varying the flow rate of metal produced by the metal source, responsive to a command signal, and sensing the operation of the apparatus and generating the command signal indicative of the operation of the apparatus. The step of atomizing may be accomplished by directing a flow of an atomizing gas at the stream of liquid metal, and then selectively controlling the flow rate of the atomizing gas.

Claims

1. Apparatus for producing an article having a uniform microstructure and a uniform macrostructure by incremental buildup of a metal by deposition of droplets of a metal spray formed from a molten metal stream, onto a substrate, comprising:

(a.) a vessel having water-cooled walls for containing molten metal, the vessel further including a nozzle for discharging a stream of molten metal from the vessel;

(b.) means for forming a metal spray from the stream of molten metal having an inlet for receiving the molten metal stream and an outlet for discharging a metal spray, said means positioned below the nozzle;

(c.) a source sensor positioned above the vessel which detects a temperature of the molten metal in the vessel and transmits a signal indicative of the temperature;

(d.) a source sensor positioned above the vessel which detects a level of the molten metal in the vessel and transmits a signal indicative of the level;

(e.) a stream temperature sensor positioned in proximity to the molten metal stream which detects the temperature of the stream before the stream enters the spray-forming means and transmits a signal indicative of the stream temperature;

(f.) a stream diameter sensor positioned in proximity to the molten metal stream which detects the stream diameter as it exits from the nozzle and transmits a signal indicative of the diameter size;

(g.) a mounting apparatus for positioning the substrate relative to the metal spray;

(h.) at least one mounting apparatus positioning sensor for indicating the position of the substrate within the mounting apparatus and which transmits a signal indicative of the substrate position;

(i.) at least one spray forming means sensor which indicates the position of the spray outlet and transmits a signal indicative of the spray outlet position;

(j.) a controller capable of receiving and transmitting signals, which determines appropriate stream diameter, stream temperature, molten metal level in the vessel, molten metal temperature in the vessel, spray direction and substrate position, and which receives sensor signals and transmits signals in response to the received signals;

(k.) a heat source positioned above the vessel, capable of receiving a signal, for adjusting the molten metal temperature in the vessel in response to the signal transmitted by the controller;

(l.) means for moving the spray forming means, capable of receiving a signal, for changing the direction of the spray in response to the signal transmitted by the controller;

(m.) means for moving the mounting apparatus, capable of receiving a signal, for changing the position of the substrate within the mounting apparatus in response to the signal transmitted by the controller; and

(n.) means for adjusting the diameter of the molten metal stream, capable of receiving a signal, for changing the diameter of the molten metal stream in response to the signal received from the controller.

2. The apparatus of claim 1 further including a melt source which provides molten metal to the molten metal-containing vessel.

3. The apparatus of claim 1 wherein the means for adjusting the molten metal stream diameter is a means for generating an electromagnetic field substantially surrounding the nozzle capable of receiving a signal, the field exerting a force on the molten stream and variable in response to a signal from the controller so that the stream diameter is adjusted to a predetermined diameter.

4. The apparatus of claim 1 wherein the heat source positioned above the vessel is a plasma torch.

5. The apparatus of claim 1 wherein the heat source positioned above the vessel is an electron beam gun.

6. The apparatus of claim 1 wherein the means for forming a metal spray from the stream comprises:

a plenum;

a gas source;

a connection between the source and the plenum to permit gas to flow from the source to the plenum;

a gas regulating means positioned between the source and the plenum capable of receiving a signal from the controller for adjusting the flow of gas into the plenum at a predetermined flow rate in response to the controller signal; and

a sensor which measures the gas flow rate and transmits a signal indicative of the flow rate to the controller.

7. The apparatus of claim 2 wherein the melt source is capable of receiving a signal and provides molten metal to the vessel as required in response to a signal from the controller to maintain the molten metal at a predetermined level within the vessel.

8. The means for generating an electromagnetic field of claim 3 wherein the means is a water-cooled current-carrying buss bar and an RF power supply.

9. The bus bar of claim 8 wherein the bar is copper.

10. The bar of claim 8 wherein the bar has a rectangular cross-section.