Processing Materials by High Power Laser M. Roth Empa ... · Materials Science &Technolog y 1 Processing Materials by High Power Laser M. Roth Empa Duebendorf . Lecture «Advanced

Materials Sci ence & Technolog y1

Processing Materials by High Power Laser M. Roth

Empa Duebendorf

Lecture «Advanced Materials and Structures» Institute of Metals Research, Shenyang, October 21-23, 2013


Laser Material Processing

Introduction - application of lasers - principle of laser - laser-processing parameters Surface treatment by laser - martensitic hardening - remelting/alloying/cladding - amorphous metals Laser welding Laser cutting Laser drilling Repair of turbine blades


Laser-principle - active medium - pumping source - resonator

Light beam - equal wave length - coherent - high density of radiation

Laser Principle

mirror partial mirror

active medium

pumping source

Laser light beam

Resonator


Induced emission

Laser Principle

Events in a laser resonator


Laser process: CO2- gas

Laser Principle

Gas-mixture: 5% CO2 15% N2 80% He


CO2- cross flow laser

Laser Principle

Gas-mixture: 5% CO2 15% N2 80% He


Laser beam: Transversale Electromagnetic Mode (TEM)

Laser Principle


CO2-Gaslaser - power: 0.5 – 18 kW - wave-length: 10.6 µm - continuous / pulsed - axial / transverse flow - beam diameter: 15 – 60 mm - TEM – mode: Gauss, multi-mode - focus-diameter: 0.2 – 0.85 mm - power density: 106-108 W/cm2



Laser processing parameters: interaction time and power density


Hardening

Welding

Cutting

Cladding

Glazing

Interaction time

Pow

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Heating up: Martensitic hardening Remelting: Remelt hardening Alloying/Cladding Welding Evaporating: Drilling / Cutting Material removal


Hardening

Welding

Cutting

Cladding

Glazing

Interaction time

Pow

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ensi

ty


Surface martensitic hardening by laser

Goal: high surface hardness against wear and erosion high toughness in the base material Materials: carbon steels, low alloy steels and tool steels, cast iron Process: - heating above austenite forming temperature - „holding-time“ long enough: diffusion of carbon - quenching to form martensite: critical cooling rate Advantage of laser hardening: - control of hardening depth - localized hardening - low distortion - fine grained microstructure, small tempering zone Martensitic hardening: typical laser processing parameters: - power: 0.5 – 3 kW - laser track: 4 – 10 mm - rate: 0.5 – 1 m/min - interaction time: 0.3 – 1 s - power density: 2 x 103 – 104 W/cm2



Hardening of low-pressure steam turbine blades Leading edge is subjected to water drop erosion due to first condensation of steam



Hardening of low-pressure steam turbine blades Optical system for constant energy distribution of the laser beam



Hardening of low-pressure steam turbine blades Microsection through laser track Material: X22CrMoV 12 1

Distance from Surface

Har

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s H

V0.1


Surface martensitic hardening by laser Hardening of low-pressure steam turbine blades Microsection through laser track: SEM-images

Distance from surface

Har

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s H

V0.1


Surface martensitic hardening by laser Hardening of low-pressure steam turbine blades Microsection through laser track: TEM-images

Distance from surface

Har

dnes

s H

V0.1



Hardening of low-pressure steam turbine blades Microsection through overlapping laser tracks



Examples for industrial applications Cylinder liners of Diesel engines



Examples for industrial applications Steering rack



Examples for industrial applications Ring groove in grey iron piston Crankshaft


Laser- surface remelting Goal: Increase resistance against: - wear - friction - erosion - fretting corrosion / wet corrosion / hot gas corrosion Materials: steels, cast steels, Ni-base alloys, Ti-, Al-alloys, …… Process: - remelting of the surface - high density of power - high cooling rates Properties of surface layer: - fine grain zone, fine dendrites - supersaturated solid solutioned crystal - metastable phases - suppression of transformations


Laser- surface remelting

Surface remelting of Ni-base superalloy:


Laser- surface remelting

Surface remelting of 12%-Cr-steel:


Laser-alloying / Laser-cladding

Materials: steels, cast iron, Ni-, Ti-, Al-alloys….. Alloying elements: Cr, WC, TiC, … gas alloying: C, N,… Coatings: MeCrAlY (Me = Ni, Co), stellite, ….. Process: - application of alloying elements - remelting of the surface - injection of powder in the laser beam Properties: - good adhesion - low porosity - dissolution of oxide particles - small interdiffusion zone


Laser-alloying / Laser-cladding Process: - application of alloying elements - remelting of the surface - Cladding: injection of powder into the laser beam

Source: IWS Dresden/Germany


Laser-cladding Cladding: injection of powder in the laser beam Stellite on carbon steel

Source: Sulzer/Switzerland


Laser-cladding Cladding: injection of powder in the laser beam Stellite on carbon steel



Laser-cladding

Cladding: injection of powder in the laser beam Stellite on carbon steel (austenitic steel) EPMA: line-scan for Co, Cr



Laser-welding

Deep-penetration mode Key hole: vapor channel inside molten pool


Laser-welding

Deep-penetration mode Key hole: vapor channel inside molten pool Welding of Ni-base superalloy


Laser-welding

Deep-penetration mode Welding of pressure sensor Ferrite-Austenite weld Exact positioning!


Removal of material by horizontal gas flow necessary!

Laser Cutting

Hardening

Welding

Cutting

Cladding

Glazing

Interaction time

Pow

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ensi

ty


Laser-cutting

High-speed cutting of sheets from ferritic steel

Processing time: 40 sec Source: Bystronic/Switzerland


Laser-cutting

High-speed cutting of sheets from ferritic steel

Processing time: 50 sec Source: Bystronic/Switzerland


Laser-cutting

Combination of stamping and laser cutting


Laser-drilling

Laser drilling of cooling holes in turbine blades Nd-YAG Laser is applied


Repair of turbine blades Blade tip restoration by laser cladding



Repair of turbine blades Contour scan of blade tip geometry


Precise restoration by laser cladding


Repair of turbine blades


Laser cladding for abrasive blade tip protection with chromised SiC-particles

Documents

Processing Materials by High Power Laser M. Roth Empa ... · Materials Science &Technolog y 1 Processing Materials by High Power Laser M. Roth Empa Duebendorf . Lecture «Advanced