CO2 LASER SURFACE TREATMENT OF BULK CERAMICS AND CERAMIC COATINGS

Información del proyecto

Identificador del acuerdo de subvención: RI1B0142

Proyecto cerrado

Fecha de inicio 1 Septiembre 1986

Fecha de finalización 31 Agosto 1990

Financiado con arreglo a

• Multiannual research and development programme (EEC) in the fields of basic technological research and the applications of new technologies (BRITE), 1985-1988

Coste total

Sin datos

Aportación de la UE

Sin datos

Coordinado por

Centre de Recherches de l'Industrie Belge de la Céramique
Belgium

Objetivo

A laser tool which is reliable, flexible and easily controlled for future process automation has been designed. The device includes a 3 kW carbon dioxide laser, a 3 axes table, power feeder and a fast pyrometer for measuring surface temperatures. The methodology was first to investigate the beam parameters and possible powder flows in single laser scan, to define optimal zones of treatment. The next step was to optimise the best treatments in multi-scanning with overlapped laser tracks to achieve suitable samples for thermo-mechanical testing.

This research programme was successful mainly for zirconiacoatings. Laser sealing and strengthening of plasma sprayed zirconia coatings could generate high performance thermal and chemical barrier coatings. For diesel engines, the next step should be testing zirconia coated piston crowns and exhaust valves in operating conditions. Concerning gas turbine engines, further investigations are required, at temperatures above 1000 C, in terms of corrosion, oxidation, erosion and thermal cycling. The possible components are combustion chambers, first stage static vanes, and possible rotor blades.

The main objective of the project was the strengthening of ceramic material by means of laser surface treatments, for use in diesel engines and gas turbine engines. For ceramic coatings, this involves surface sealing, and improvement of mechanical properties in terms of thermal shock, erosion and abrasion. For bulk ceramics, surface flaws need to be mended and fracture toughness improved in order to prevent the formation or to limit the propagation of cracks when the materials are subjected to external stresses.

The surface treatments were carried out using an industrial 3kW continuous carbon dioxide laser. Treatment optimization required the adjustment of beam power and scan rate (3 axes table). Atmospheric control was achieved by the gas flow used to protect the focusing lens, provided the structure of laser nozzle is suitable. Surface temperatures were recorded in real time by a fast dichromatic pyrometer coupled to an amplifier and a microcomputer. A powder feeder was connected to the laser nozzle for reactive laser treatments involving powder projection in the laser beam.

The best results were obtained with zirconia coatings, made by plasma spraying yttria stabilized zirconia on cast iron or inconel substrates, using nickel chromium aluminium yttritium as a bond coat in order to reduce expansion coefficient mismatches. The porous as sprayed coatings are very efficient thermal barriers, but their mechanical properties are poor and they are not impervious to corrosive gases. 2 processes were therefore investigated and optimized. Laser sealing was achieved by rapid surface melting and solidification which generated dense surface layers with fine and homogeneous microstructures. However the mechanical improvements were limited by surface cracks due to shrinkage and differential stresses. Surface cracking was controlled in the laser strengthening process by projecting alumina powder during surface melting. Additional advantages of the composite surfaces obtain ed are higher hardness and greater chemical resistance.
THE BRITTLENESS OF CERAMIC MATERIALS LIMITS THEIR USE IN HEAT ENGINES. AS FAILURE OFTEN OCCURS FROM SURFACE FLAWS, THE PURPOSE OF THIS PROJECT IS TO INVESTIGATE SURFACE LASER TREATMENTS FOR HEALING SURFACE FLAWS AND-OR FORMING RESIDUAL COMPRESSIVE STRESSES TO IMPROVE SURFACE TOUGHNESS.
IN THE PARTICULAR CASE OF CERAMIC COATINGS, THE FIRST GOAL IS TO SEAL THE SURFACE FOR ENHANCING CORROSION RESISTANCE, AND SECONDLY TO GET FINER AND HOMOGENEOUS MICROSTRUCTURES FOR IMPROVING THERMAL SHOCK AND EROSION RESISTANCE.
THE FIRST APPLICATION SHOULD BE A BETTER HEAT PROTECTION OF DIESEL COMPONENTS WHICH ARE IN CONTACT WITH HOT GASES (PISTON, VALVES).

Ámbito científico (EuroSciVoc)

• ciencias naturales › ciencias químicas › química inorgánica › metales de transición
• ciencias naturales › ciencias químicas › química inorgánica › metales de postransición
• ingeniería y tecnología › ingeniería de materiales › recubrimiento y películas
• ingeniería y tecnología › ingeniería de materiales › cerámica
• ciencias naturales › ciencias físicas › óptica › física del láser

Programa(s)

• FP1-BRITE - Multiannual research and development programme (EEC) in the fields of basic technological research and the applications of new technologies (BRITE), 1985-1988

Tema(s)

Datos no disponibles

Convocatoria de propuestas

Datos no disponibles

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

Centre de Recherches de l'Industrie Belge de la Céramique

• Aportación de la UE: Sin datos
• Dirección: Avenue Gouverneur Cornez ; 7000 Mons ; Bélgica
• Coste total: Sin datos

Participantes (3)

Compagnie Générale d'Electricité (CGE)

Francia

• Aportación de la UE: Sin datos
• Dirección: Route de Nozay ; 91460 Marcoussis
• Coste total: Sin datos

Deutscher Verband für SchweißtechnikeV

Alemania

• Aportación de la UE: Sin datos
• Dirección: Aachener Straße 172 ; 40223 Düsseldorf
• Coste total: Sin datos

Société d'Etudes de Machines Thermiques SA - SEMT PIELSTICK

Francia

• Aportación de la UE: Sin datos
• Dirección: 2 Quai de Seine ; 93202 Saint-Denis
• Coste total: Sin datos