Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Laser cladding of complex nano-structured powders

Laser Cladding
Technology of laser cladding through coaxial nozzle to fabricate coatings with tailored properties is developed. Two methods of wear-resistant coatings deposition were employed: injection of powder into the melting pool, created by laser beam and laser cladding from pre-deposited layers. Special coaxial nozzle has been developed to realise deposition process. The following powder blends were tested: FeCu (60/40 %Wgt) nano-composite alloy powder; FeCu+WC/Ni(802/0 %Vol); CuSn (50/50 %Vol) alloy; CuSn+WC/Ni (80/20 %Vol); FeCu+WC/Ni (80/20%Vol); FeCu (60/40 % Vol); WC/Ni (83/17 %Vol) and several others.

The coating Stellite/ CuSn/ nanoWC/ Co with Solid Lubricant matrix reinforced both by internal structure (Stellite lines) and dispersed ceramic phase have shown the best performance with stable dry friction coefficient 0.12. The main components distribution for that coating shows gradual change in their concentrations: decrease of Cu and Sn and increase of WC from the surface to the depth 100mm. It is proved that radiation mode is one of the critical parameters defining the coating¿s microstructure (and thus, wear properties). Application of pulsed-periodic mode provides much better component remixing (e.g. in a case of coatings producing from Metal Matrix Composites) in comparison with continuous wave mode. It is proved that the different modes of laser action and affect coating microstructure (for the same composition) and result in different friction coefficients - 0.45 and 0.25 for continuous wave and pulsed-periodic mode, correspondingly.

Laser Alloying
Different methods of alloying of aluminium and iron were tested. Original techniques (in particular, multi-layer coatings deposition) were employed in order to provide uniform distribution of doping elements, micro-hardness, tribologic properties, etc of the modified layers. Laser alloying of systems with great differences in physico-chemical properties such as: Al-Sn(In, Pb, Fe), Fe-Sn(Pb), Al-Fe-Sn was performed. Various types of laser surface treatment (continuous wave and pulse-periodic Nd:YAG lasers) were utilised and related to modified zone properties.

Present research employed different original methods of samples preparation:
(a) the collage of a sheet of the metal to be deposited;
(b) the insertion by pressure or by melting of a wire containing the alloying elements inside a triangular groove on the substrate;
(c) the pre-deposition of multi-layer coatings: pressing on the base material surface, several sanded metallic films (50µm thick);and
(d) the application of powder mixture instead of metallic films.

Current status of the results: the most promising coatings are under detail examination of structure and optimisation of laser cladding parameters.

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