Device and method for remelting metallic surfaces

Abstract

A method for remelting metallic surfaces of components using the effect of a stable high pressure plasma jet, includes melting the surface in localized areas, the surface having a structure refinement after solidification. The plasma jet action is generated by the microwave impact on a carrier gas, the pressure of the high pressure plasma jet being above the atmospheric pressure. In addition, a plasma torch for generating a directed high pressure plasma jet includes a gas supply, a device for generating a plasma, and an outlet nozzle for a plasma jet. The device for generating the plasma includes a magnetron and a resonator in which the supplied pressurized carrier gas is transferred into a plasma under the effect of microwaves, causing the plasma to exit through the outlet nozzle at a pressure above 0.1 MPa.

1 . A method for remelting a metallic surface subjected to thermal-mechanical stress during use, the method comprising:
 generating a plasma jet using microwave impact on a carrier gas so as to generate a high pressure plasma jet having a pressure higher than atmospheric pressure;   applying the plasma jet to the metallic surface in a localized area so as to remelt a surface layer; and   allowing the surface layer to solidify, thereby undergoing a structure refinement, the solidified surface layer being structurally refined in comparison with the surface layer before the plasma jet was applied to the metallic surface.   
     
     
         2 . The method as recited in  claim 1 , wherein the pressure of the plasma jet is from 0.1 MPa to 0.8 MPa. 
     
     
         3 . The method as recited in  claim 1 , wherein the carrier gas includes at least one of the gases He, Ar, N 2 , H 2 , O 2 , CO 2 , H 2 O, CH 4  and C 2 H 6 . 
     
     
         4 . The method as recited in  claim 1 , wherein the carrier gas is formed by air. 
     
     
         5 . The method as recited in  claim 1 , wherein the plasma jet has a length greater than 5 cm. 
     
     
         6 . The method as recited in  claim 1 , wherein the plasma jet is expanded in a fan-shaped manner. 
     
     
         7 . The method as recited in  claim 1 , further comprising supplying substances to the plasma jet between a nozzle outlet aperture and the metallic surface. 
     
     
         8 . The method as recited in  claim 7 , wherein the substances are solid substances formed by ceramic powders. 
     
     
         9 . The method as recited in  claim 7 , wherein the substances are liquid substances formed by metal-organic solutions or metal salt solutions. 
     
     
         10 . The method as recited in  claim 7 , wherein the substances include at least one of solid and liquid substances and wherein the substances form solid particles in the remelted surface layer, the particles being consisting essentially of at least one of Al 2 O 3 , AlN, MgO, SiC and Si 3 N 4 . 
     
     
         11 . The method as recited in  claim 1 , wherein the plasma jet has a power density from 6 kW/cm 2  to 20 kW/cm 2  and wherein the applying includes moving the plasma jet over the surface at a speed of from 2 mm/sec to 4 mm/sec. 
     
     
         12 . The method as recited in  claim 1 , wherein the plasma jet has a power density from 20 kW/cm 2  to 60 kW/cm 2  range and wherein the applying includes moving the plasma jet over the surface at a speed of from 3 mm/sec to 10 mm/sec. 
     
     
         13 . The method as recited in  claim 1 , wherein the metallic surface is formed by a light metal alloy. 
     
     
         14 . The method as recited in  claim 1  wherein the surface refinement enhances a surface hardness, a surface strength or a surface ductility of the surface layer in comparison with the surface hardness, the surface strength or the surface ductility of the surface layer before the plasma jet was applied to the metallic surface.