Energy Density Effect of Laser Alloyed TiB2/TiC/Al Composite Coatings on LMZ/HAZ, Mechanical and Corrosion Properties

In the present work, TiC/TiB2/Al composite coatings were synthesized onto a precipitation hardened AlSi1MgMn alloy by laser surface alloying (LSA), using 13.3 J/mm2 and 20 J/mm2 laser energy densities. Microstructure evaluation, microhardness, wear and corrosion performance were investigated and com...

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Bibliographic Details
Published in:Metals (Basel ) 2020-03, Vol.10 (3), p.411
Main Authors: Ravnikar, Dunja, Trdan, Uroš, Nagode, Aleš, Šturm, Roman
Format: Article
Language:English
Subjects:
Aluminum base alloys
Aqueous solutions
ceramic coatings on al alloy
Ceramic glazes
Ceramics
Chemical precipitation
Coatings
corrosion
Corrosion currents
Corrosion resistance
Corrosive wear
Crystallography
Flux density
Heat affected zone
Laser beam melting
laser melted/heat affected zone (lmz/haz)
laser surface alloying (lsa)
Lasers
Microhardness
Microstructure
Overheating
Particle size
Porosity
Precipitates
Prohibition
Protective coatings
Substrates
Surface alloying
Titanium alloys
Titanium diboride
wear
Wear resistance
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Summary:In the present work, TiC/TiB2/Al composite coatings were synthesized onto a precipitation hardened AlSi1MgMn alloy by laser surface alloying (LSA), using 13.3 J/mm2 and 20 J/mm2 laser energy densities. Microstructure evaluation, microhardness, wear and corrosion performance were investigated and compared with the untreated/substrate Al alloy sample. The results confirmed sound, compact, crackles composite coating of low porosity, with a proper surface/substrate interface. Microstructural analyses revealed the formation of extremely fine nano-precipitates, ranging from of 50–250 nm in the laser melted (LMZ) and large precipitates, accompanied with grain coarsening in the heat-affected zone (HAZ), due to the substrate overheating during the LSA process. Nonetheless, both coatings achieved higher microhardness, with almost 7-times higher wear resistance than the untreated sample as a consequence of high fraction volume of hard, wear resistant TiB2 and TiC phases inside the composite coatings. Further, cyclic polarization results in 0.5 M NaCl aqueous solution confirmed general improvement of corrosion resistance after LSA processed samples, with reduced corrosion current by more than a factor of 9, enhanced passivation/repassivation ability and complete prohibition of crystallographic pitting, which was detected with the untreated Al alloy.
ISSN:2075-4701
2075-4701
DOI:10.3390/met10030411