Turbine Element Repair

Abstract

Ion-enhanced physical vapor deposition is utilized to deposit repair material on Ti alloy turbine parts. Pulse modulation may be used to control a bias voltage and an ionization.

1 . An apparatus for depositing material on a workpiece comprising:
 a deposition chamber;   a deposition material source;   means for forming a plasma from said deposition material source;   means for applying a modulated bias electric potential to the workpiece to draw ions from the plasma to the workpiece;   means for monitoring a density of the plasma and an ion current to the workpiece; and   a control system coupled to the means for forming, means for applying, and means for monitoring and programmed so as to provide feedback loop control of deposition of the material.   
   
   
       2 . The apparatus of  claim 1  further comprising:
 means for heating the workpiece.   
   
   
       3 . The apparatus of  claim 2  wherein:
 the means for heating the workpiece comprises an electron beam source positioned to direct a second electron beam to the workpiece.   
   
   
       4 . The apparatus of  claim 2  wherein:
 the control system is programmed to control the means for heating the workpiece so as to provide a modulated heating.   
   
   
       5 . The apparatus of  claim 1  wherein:
 the control system is programmed to control the means for applying a modulated bias electric potential so as to prevent arcing from the workpiece.   
   
   
       6 . The apparatus of  claim 1  wherein:
 the control system is programmed to control the means for applying a modulated bias electric potential so as to:
 maintain a principally negative potential; and 
 apply positive pulses of relatively short duration. 
   
   
   
       7 . An apparatus for depositing material on a workpiece comprising:
 a deposition chamber;   deposition material at least partially within the deposition chamber;   a first electron beam source, positioned to direct a first electron beam to vaporize a portion of the deposition material;   an ionizing electrode and an electromagnetic coil surrounding a flowpath from the deposition material;   a bias voltage source connected to apply an electric potential to the workpiece; and   a control apparatus coupled to the bias voltage source and configured to apply said electric potential as a principally negative potential interspersed with positive pulses.   
   
   
       8 . The apparatus of  claim 7  wherein:
 the control apparatus is coupled to the ionizing electrode for pulse modulation of ionization.   
   
   
       9 . The apparatus of  claim 7  wherein:
 the control apparatus is programmed to control the bias voltage source so as to prevent arcing from the workpiece.   
   
   
       10 . The apparatus of  claim 7  wherein:
 the bias voltage source comprises an electronic tube acting to limit current to the workpiece.   
   
   
       11 . The apparatus of  claim 7  further comprising:
 a second electron beam source positioned to direct a second electron beam to the workpiece.   
   
   
       12 . The apparatus of  claim 7  wherein:
 the deposition material comprises Ti, Al, and V.   
   
   
       13 . The apparatus of  claim 7  wherein:
 the control apparatus is programmed to control the bias voltage source so as to apply the first potential with:
 a nominal voltage of 50V-10 kV; 
   a pulse repetition frequency of 0.05-150 kHz;   a pulse width of at least 5 μs; and   a duty cycle of 0.1-0.99   
   
   
       14 . The apparatus of  claim 13  wherein:
 the nominal voltage is 1-3 kV; and   the pulse repetition frequency is 0.5-5 kHz; and   
   
   
       15 . The apparatus of  claim 7  wherein:
 the control apparatus is programmed to provide an ion current density of 1-50 mA/cm 2  at a deposition rate of 10-50 μm/minute.   the ion current density is 2-10 mA/cm 2  at a deposition rate of 15-20 μm/minute.   
   
   
       16 . The method of  claim 7  wherein:
 the ionizing is pulse modulated with a pulse repetition frequency of 100-1000 Hz and a duty cycle of 0.5-0.9.   
   
   
       17 . A repaired metallic part comprising:
 a substrate; and   a repair material having a first interface with the substrate, a bond strength between the repair material and the substrate being in excess of 50 ksi.   
   
   
       18 . The part of  claim 17  wherein the repair material is a first repair material and wherein the part further comprises:
 a second repair material having a second interface with the substrate and a third interface with the first repair material, second and third bond strengths between the second repair material and the substrate and first repair material, respectively, being in excess of 50 ksi.   
   
   
       19 . The part of  claim 17  wherein:
 the substrate and the repair material comprise Ti alloys or nickel- or cobalt-based superalloys of like nominal composition;   the bond strength is between 100 ksi and 200 ksi;   the repair material has a depth of at least 2.0 mm;   the substrate has a thickness in excess of the depth of the repair material; and   the substrate comprises original unrepaired material.