laser cladding
DESCRIPTION
laserTRANSCRIPT
ILT
Laser cladding
Process
Laser cladding is a deposition weldingprocess in which a layer of powder isdeposited on the substrate material,and the two materials are fused by me-tallurgical bonding through the actionof a laser beam. The characteristic features of this process are:• highly precise, automated deposition
of a layer of material with a thicknessvarying between 0.1 millimeters and several centimeters
• metallurgical bonding of the claddingmaterial with the base material
• absence of undercutting• low heat input into the substrate• a wide selection of homologous and
non-homologous powder materials• the ability to process virtually any
type of metal alloy
By varying the process parameters andselecting different powder materials, a component’s surface can be either alloyed or cladded with a carbide or similar coating. Typical deposition rateslie in the region of several cm2 per minute for layers with a thickness of around 1 mm.
Applications
The main fields of application are to be found in machine-tool and plant en-gineering, and engine manufacturingfor the aircraft and automotive industries.
Laser cladding can be used for a widevariety of purposes, including the ap-plication of wear-resistant or anticorrosion coatings, the repair of worn orpoorly machined workpieces, depositionwelding of shaped parts, and the com-plete manufacture of 3-D components.
Laser systems
Laser cladding systems employ CO2,Nd:YAG or diode lasers with an outputof between 100 watts and several kilowatts, operating in pulsed or conti-nuous mode. Cartesian systems with3-5 axes and robotic manipulators areemployed as handling systems.
NC programs are produced in severalways, either by• direct input of the CAD data for the
component, or by• mapping the geometry of the
components in an automated digital process, or by
• teaching of the NC paths.
In a downstream step, CAM softwarespecifically designed to accommodatethe specific built-up strategies requiredfor laser cladding generates the NCprograms and post-processes the datafor use in different manufacturing set-ups.
Different powder feeding systems areused, depending on the complexityand the accessibility of the parts to beprocessed.
Above: Laser-clad mold insert.Middle: Laser-welded rough-processed substrate for brake-disk prototypes.Below: Repair of a separator drum.
Process and applications
Laser-clad high-pressure turbineblade (TIP repair).
In laser cladding by powder deposition,the way in which the powder is intro-duced into the melt pool is of greatimportance. This factor significantly affects the consumption of powdermaterial, the extent to which oxidationoccurs through reaction with the sur-rounding atmosphere, and the rough-ness of the cladded layer. Researchersat the Fraunhofer ILT and the Chair forLaser Technology LLT at RWTH AachenUniversity have developed a number of concepts for powder nozzles andimplemented them in industrial-scaleproducts. The nozzles are based on a modular structure that allows indivi-dual components to be replaced simplyand quickly. The integrated water-cooling system allows the nozzles toremain in continuous service for severalhours.
Off-axis powder nozzle
In the off-axis powder nozzle, the powder is introduced laterally into thepath of the laser beam. The nozzle’smain features are:• Impingement angle variable between
50° and 80°• Excellent accessibility to the compo-
nent by small design of the nozzle (width 3 mm)
• Choice of modular nozzles with circular and rectangular injection openings
Discrete coaxial nozzle
In the discrete coaxial nozzle, a com-posite beam consisting of at least threeside beams running coaxially to the laser beam is used to create a powderfocus. Its most important features are:• capacity for 3-D processing, in which
the nozzle is slanted by up to 180°• especially suited to the cladding
of broad tracks (2 - 7 mm)• integrated shielding gas control
Continuous-feed coaxial nozzle
In continuous-feed powder injection,the powder is applied through a coni-cal ring-shaped cavity that narrows as it approaches the tip of the nozzle.As a result, the powder is deposited ina donut-shaped cone around the laserbeam. The continuous-feed nozzle en-ables the powder focus to be reducedto approx. 1 mm. Its most importantfeatures are:• 3-D machining possible, with the
nozzle slanted by up to 20°.• particularly well suited to the
cladding of narrow tracks (< 1 mm).• integrated shielding gas control.
Special optics for processinginternal contours
A special optical system with its ownpowder feed unit has been developedfor hardening and cladding applica-tions. It is designed for use with a fiber-coupled laser with an output of up to3 kW. It is capable of processing com-ponents with an internal diameter of50 mm or greater.
Powder feed nozzles
Optical system for processing internal contours.
5 cm
Above: Off-axis powder nozzle with positioning unit.Middle: Discrete coaxial nozzle(»three-way nozzle«) with HighYAGoptics for fiber-coupled diode laser.Below: Continuous-feed coaxialnozzle.
5 cm
5 cm
5 cm
DQS certified by DIN EN ISO 9001Reg.-No.: DE-69572-01
Fraunhofer-Institut für Lasertechnik ILT
DirectorProf. Dr. rer. nat. Reinhart Poprawe M.A.
Steinbachstraße 1552074 AachenPhone: +49 (0)241/8906-0Fax: +49 (0)241/8906-121
Subject to alterations in specifications and other technical information.06/2007.
With 58 research institutes, 12.700employees and over 1 billion euros research budget, the Fraunhofer-Gesellschaft belongs to one of the leading organizations in Europe forcontract research. Fraunhofer’s expertsdevelop technical and organizationalsolutions to the problems set by indus-trial contractors up to the installationof complete systems.
The Fraunhofer-Institut für LasertechnikILT (Fraunhofer Institute for Laser Tech-nology) develops methods and systemsfor laser material processing and lasermeasuring technology within the frame-work of R&D contracts. The know-howof 250 employees as well as state-of-the-art technology are made availableto the contractor.
Our services
Use the know-how of our experts. We offer you solutions which are tailor-made for your applications:
• independent advice• feasibility and economic viability
studies• support of patent research and
applications• small-lot production• individual prototype construction• development and construction of
special machines and plants• installation and testing of pilot
plants• training of service personnel• information seminars for executives
Contact
Dr. Konrad WissenbachPhone: +49 (0)241/[email protected]
Dipl.-Ing. Gerhard BackesPhone: +49 (0)241/[email protected]
Dr. Andres GasserPhone: +49 (0)241/[email protected]
Akad. Rat z. A. Dr. Ingomar KelbassaPhone: +49 (0)241/[email protected]
Dr. Andreas WeisheitPhone: +49 (0)241/[email protected]
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