Laser cladding of tubes

Abstract

The present invention relates to an apparatus for laser cladding of a curved surface comprising: (a) an elongated arm having first and second ends and defining a chamber through the arm from the first end to the second end; (b) a laser delivery source connected to a focusing lens mounted in a housing within an opening on the first end of the arm for delivering a laser beam through the chamber; (c) a delivery head mounted on the second end of the arm comprised of (i) an enclosure having an inlet for receiving the laser and an outlet for delivering the laser to the curved surface, (ii) a powder nozzle for delivering a cladding powder to an inner surface of the curved surface, and (iii) a reflective surface for reflecting the laser to exit through the outlet; (d) mounting means for rotating the curved surface for the cladding of the curved surface; and (e) indexing means for moving the arm substantially parallel to a longitudinal axis of the curved surface so as to clad the curved surface during the rotation of the curved surface. Typically, the curved surface is part of the inner surface of a tube used in industrial applications.

1 . An apparatus for laser cladding of a curved surface comprising:
 (a) an elongated arm having first and second ends and defining a chamber through the arm from the first end to the second end;   (b) a laser delivery source connected to a focusing lens mounted in a housing within an opening on the first end of the arm for delivering a laser beam through the chamber;   (c) a delivery head mounted on the second end of the arm comprised of (i) an enclosure having an inlet for receiving the laser and an outlet as a laser nozzle for delivering the laser to the curved surface, (ii) a diffuser nozzle for delivering a cladding powder to an inner surface of the curved surface, and (iii) a reflective surface for reflecting the laser to exit through the outlet;   (d) mounting means for rotating the curved surface for the cladding of the curved surface;   (e) indexing means for moving the arm substantially parallel to a longitudinal axis of the curved surface so as to clad the curved surface during the rotation of the curved surface.   
   
   
       2 . The apparatus of  claim 1  wherein, the curved surface is at least a portion of an inner surface of a tube. 
   
   
       3 . The apparatus of  claim 1 , wherein the reflective surface is selected from group consisting of a mirror, copper, and fused silica coated with anti-reflective coating. 
   
   
       4 . The apparatus of  claim 1 , wherein the diffuser is operable to deliver the cladding powder and a carrier gas to the curved surface, and wherein the powder and carrier gas are each fed from an external powder source and a carrier gas source respectively through and along a powder/gas pathway defined in the elongated arm and exit through the diffuser nozzle. 
   
   
       5 . The apparatus of  claim 4 , wherein the diffuser is adapted to allow for the carrier gas to be delivered in excess to reduce powder velocity. 
   
   
       6 . The apparatus of  claim 1 , wherein the elongated arm further defines water channels in the chamber operable to allow for water cooling of the focusing lens and maintaining the operating temperature of the cladding head between 25 and 50° C. 
   
   
       7 . The apparatus of  claim 1 , further comprising a cover glass adjacent the laser nozzle in the housing adapted to reduce dust and back-spatter resulting from the cladding. 
   
   
       8 . The apparatus of  claim 7 , wherein the reflective surface and the cover glass are each removably mounted within the housing. 
   
   
       9 . The apparatus of  claim 7 , wherein: (i) the elongated arm further defines a shield gas pathway running parallel to a longitudinal axis of the elongated arm sized for allowing shield gas to be delivered to the laser nozzle; (ii) the laser nozzle defines a small slit sized to increase shield gas velocity; and (iii) the shield gas is operable to reduce back-spatter velocity entering the laser nozzle. 
   
   
       10 . The apparatus of  claims 1 , further comprising a temperature sensor in the head for temperature monitoring of the laser cladding. 
   
   
       11 . The apparatus of  claim 1 , further comprising a thermal switch adapted to turn off the laser when the temperature in the housing rises above a set point. 
   
   
       12 . The apparatus of  claim 1 , wherein the curved surface is adapted to be rotated and the apparatus is adapted to be indexed parallel to a longitudinal axis of the curved surface and movement of each of the curved surface and the apparatus with respect to each other is preset to achieve a predetermined cladding thickness. 
   
   
       13 . The apparatus of  claim 12 , wherein the preset movement of each of the curved surface and the elongated arm is controlled by a programmable robotic source. 
   
   
       14 . The apparatus of  claim 1 , wherein the apparatus is operable for cladding overlapping from 40 to 50% of a previous cladding and deposits a thickness from 0.15 mm to 3 mm onto the inner surface of the tube. 
   
   
       15 . The apparatus of  claim 1 , wherein the cladding powder is 60-40 Tungsten carbide and Nickel based powder. 
   
   
       16 . The apparatus of  claims 1 , wherein the delivery head is constructed from a member selected from the group consisting of copper, copper-beryllium alloy and combinations thereof. 
   
   
       17 . A process for laser cladding, which comprises:
 (a) providing an apparatus for laser cladding the inner diameter of a curved surface which comprises:
 (1) an elongated arm having first and second ends and defining a chamber through the arm from the first end to the second end; 
 (2) a laser delivery source connected to a focusing lens mounted in a housing within an opening on the first end of the arm for delivering a laser beam through the chamber; 
 (3) a delivery head mounted on the second end of the arm comprised of: (i) an enclosure having an inlet for receiving the laser and an outlet as a laser nozzle for delivering the laser to the curved surface; (ii) a diffuser nozzle for delivering a cladding powder to an inner surface of the curved surface; and (iii) a reflective surface for reflecting the laser to exit through the outlet; 
 (4) mounting means for rotating the curved surface for the cladding of the curved surface; 
 (5) indexing means for moving the arm substantially parallel to a longitudinal axis of the curved surface so as to clad the curved surface during the rotation of the curved surface; and 
   (b) cladding the curved surface by indexing the elongated arm to coat the curved surface with the cladding.   
   
   
       18 . The process of  claim 17 , wherein the curved surface is at least a portion of an inner surface of a tube. 
   
   
       19 . The process of  claim 17 , wherein: (i) the cladding powder and a carrier gas are delivered to the curved surface from the diffuser; (ii) the powder and the carrier gas are each fed from an external powder source and carrier gas source respectively through and along a powder/gas pathway defined in the elongated arm and exit through the diffuser nozzle; and (iii) the carrier gas is delivered in excess operable to reduce powder velocity. 
   
   
       20 . The process of  claim 17 , wherein the apparatus further comprises a cover glass adjacent the laser nozzle in the housing adapted to reduce dust and back-spatter resulting from the cladding. 
   
   
       21 . The process of  claim 20 , wherein the reflective surface and the cover glass are each removably mounted within the housing. 
   
   
       22 . The process of  claim 20 , further comprises a shield gas passing from the first end to the second end of the elongated arm and exiting through a small slit defined in the laser nozzle and adapted to increase gas velocity, wherein the shield gas is operable to reduce back-spatter velocity in the laser nozzle. 
   
   
       23 . The process of  claims 17 , wherein the delivery head further comprises a temperature sensor in the head for temperature monitoring of the laser cladding. 
   
   
       24 . The process of  claims 17 , wherein the delivery head further comprises a thermal switch adapted to turn off the laser when the temperature in the housing rises above a set point. 
   
   
       25 . The process of  claim 17 , further comprising rotating the curved surface and indexing the apparatus parallel with a longitudinal axis of the curved surface, wherein the movement of each of the curved surface and the apparatus with respect to each other is preset to achieve a predetermined cladding thickness. 
   
   
       26 . The process of  claim 25 , wherein the preset movement of each of the curved surface and the elongated arm is controlled by a programmable robotic source. 
   
   
       27 . A cladding head apparatus adapted for laser cladding of a surface comprising:
 (a) an enclosure having an inlet for receiving a laser and an outlet as a laser nozzle for delivering the laser to the surface,   (b) a diffuser mounted adjacent to the enclosure having a diffuser nozzle for delivering a cladding powder to the surface;   (c) a reflective surface for reflecting the laser to exit through the outlet;   (d) a cover glass within the enclosure mounted adjacent to the laser nozzle for reducing dust and back spatter resulting from the cladding of the surface;   wherein the cover glass and the reflective surface are each removably mounted within the enclosure.   
   
   
       28 . The apparatus of  claim 27 , wherein the cladding head is mounted on a second end of an elongated arm defining a chamber and coupled to a laser energy source at an opposite first end, the chamber is constructed to allow for the laser to be transmitted through the elongated arm and into the inlet of the enclosure of the cladding head. 
   
   
       29 . The apparatus of  claim 28 , wherein the reflective surface is adapted to reflect the laser perpendicular to a longitudinal axis defined by the elongated arm. 
   
   
       30 . The apparatus of  claim 27 , wherein each of the cover glass and the reflective surface is mounted on a removable insert member such that each of the cover glass and the reflective surface is replaceable. 
   
   
       31 . The apparatus of  claim 27 , wherein the reflective surface is selected from group consisting of a mirror, copper, and fused silica coated with anti-reflective coating. 
   
   
       32 . The apparatus of  claim 27 , wherein the diffuser is operable to deliver the cladding powder and a carrier gas to the surface, and wherein the powder and carrier gas are each fed from an external powder source and a carrier gas source respectively and exit through the diffuser nozzle. 
   
   
       33 . The apparatus of  claim 27 , further comprising shield gas delivery means for delivering shield gas to the laser nozzle wherein: (i) the laser nozzle defines a small slit sized to increase shield gas velocity; and (ii) the shield gas is operable to reduce back-spatter velocity entering the laser nozzle. 
   
   
       34 . The apparatus of  claims 27 , further comprising a temperature sensor mounted in the enclosure for temperature monitoring of the laser cladding. 
   
   
       35 . The apparatus of  claim 34 , further comprising a thermal switch adapted to turn off the laser when the temperature in the housing rises above a set point.