High power fiber laser effusion hole drilling apparatus and method of using same

Abstract

A fiber laser-treated workpiece is configured with a body having a discontinuous surface which defines a plurality of spaced through-going passages so that each passage is delimited by a peripheral layer having a surface characteristic which includes a recast layer or one or more microcracks or a combination thereof. The passages are provided by a high power Yb fiber laser operating in a pulsed regime and configured to output either a single pulse per an entire passage or a train of pulses per the passage. The Yb fiber laser is so configured that, if formed, the recast layer and micro-crack each are smaller than respective standards in an airspace industry.

1 . A fiber laser-treated workpiece comprising a discontinued body defining a plurality of spaced through-going passages, each passage being delimited by a peripheral layer having a surface characteristic which includes a recast layer and one or more micro cracks, wherein, if formed, the recast layer depth and micro crack width each are smaller than respective standards in an airspace industry. 
     
     
         2 . The fiber laser-treated workpiece of  claim 1 , wherein the industry standards for a recast layer thickness and a micro-crack width are respectively 0.005″ and 0.0015″. 
     
     
         3 . The fiber laser-treated workpiece of  claim 1 , wherein the thickness of the recast layer varies between about 0.0015″ and about 0.0025″ and a micro-crack width varies between about 0.0002″ and about 0.001″. 
     
     
         4 . The fiber laser-treated workpiece of  claim 1 , wherein the body made from material selected from the group consisting of aluminum, ceramics, metallo-ceramics, nickel alloys, stainless steels, titanium and a combination thereof. 
     
     
         5 . The fiber laser-treated workpiece of  claim 1 , wherein the body has a configuration selected from the group consisting of turbine blades, nozzle, guide vanes, combustion chambers and afterburner. 
     
     
         6 . The fiber laser-treated workpiece of  claim 1 , wherein the spaced passages have respective substantially uniform diameters and tapers, the peripheral layers each being free from splatter and having clean and substantially uniform exit and an entrance free from irregularities. 
     
     
         7 . The fiber laser-treated workpiece of  claim 6 , the spaced passages having substantially uniform openings having a standard deviation less than x. 
     
     
         8 . A method of drilling a workpiece, comprising:
 controllably displacing the workpiece and single mode high power fiber laser relative to one another among a plurality of predetermined locations along a path; and   periodically firing the fiber laser at each of the locations, thereby outputting at least one pulse incident on the location so as to drill a plurality of through-going spaced passages in the workpiece, the at least one pulse having optical characteristics selected so that a recast layer, if formed on a periphery defining a passage, and one or more micro cracks, if formed in the recast layer, have a thickness and a width, respectively, smaller than respective standards for an aerospace industry.   
     
     
         9 . The method of  claim 8 , wherein the periodic :firing of the fiber laser includes outputting single one pulse per each location, the one pulse being shaped and configured to drill an entire passage. 
     
     
         10 . The method of  claim 9 , wherein one pulse at each location has a pulse width of about 10 milliseconds, a square shape, a peak power varying between 6 kW and about 20 kW. 
     
     
         11 . The method of  claim 8 , wherein the periodic firing of the fiber laser includes outputting a plurality of pulses per each location at a repetition rate varying between about 25 Hz and about 50 Hz. 
     
     
         12 . The method of  claim 11 , wherein the outputting of the pulses includes configuring uniform square pulses each having a pulse width between 0.5 to about 3 milliseconds. 
     
     
         13 . The method of  claim 12 , wherein the outputting of the uniform pulses occurs in substantially a fundamental mode having substantially uniform parameters which include an M2 value, focal point, spot size, and peak power ranging between about 6 kW and about 20 kW. 
     
     
         14 . The method of  claim 8 , wherein the standards for the thickness and width are about 0.0015″ and about 0.0005″, respectively. 
     
     
         15 . A laser system for drilling a body of a workpiece, the laser system comprising a high power Yb fiber laser operative to emit a plurality of discreet pulses incident on selected locations on the body and configured to provide a plurality of through-going and substantially uniform spaced passages at respective locations, the passage each being defined by a periphery, the pulses each having parameters selected so that a recast layer, if formed on the periphery, and one or more microcracks, if formed in the recast layer, have a thickness and a width, respectively, smaller than respective standards for an aerospace industry. 
     
     
         16 . The laser system of  claim 15 , wherein the standards for a recast layer thickness and a micro-crack width are respectively 0.005″ and 0.0015″. 
     
     
         17 . The laser system of  claim 15 , wherein the fiber laser is so configured that a single discreet pulse has parameters sufficient to drill an entire passage. 
     
     
         18 . The laser system of  claim 17 , wherein the single discreet pulse has the parameters including a square shape, pulse width of at least 10 milliseconds, and a peak power of at least . . . , the parameters are so selected that the peripheries of the respective passages are tapered at a substantially uniform angle, have a substantially uniform diameter, free form splatter and have a clean and substantially uniform exit and an entrance free from irregularities. 
     
     
         19 . The laser system of  claim 15 , wherein the fiber laser is configured to emit a train of the discreet pulses for a single passage, the pulses each having substantially uniform parameters including a square shape and a pulse width varying between about 0.5 to about 3 milliseconds, the parameters being so selected that the peripheries of the respective passages are tapered at a substantially uniform angle, have a substantially uniform diameter, free from splatter and have a clean and substantially uniform exit and an entrance free from irregularities. 
     
     
         20 . The laser system of  claim 15 , wherein the fiber laser is operative to output the discreet pulses at a repetition rate between about 25 and about 50 Hz and a peak power varying between about 6 kW and 20 kW. 
     
     
         21 . The laser system of  claim 15 , wherein the high power single mode Yb fiber laser is configured with a plurality of modules optically coupled to one another and each having an Yb doped oscillator output radiation with a substantially uniform M 2  value, substantially uniform focal point and spot size, and substantially uniform peak power ranging between about 6 kW and about 20 kW.