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Open AccessArticle

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

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Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia
2
Faculty of Natural Sciences and Engeneering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
*
Author to whom correspondence should be addressed.
Metals 2020, 10(3), 411; https://doi.org/10.3390/met10030411
Received: 17 February 2020 / Revised: 12 March 2020 / Accepted: 18 March 2020 / Published: 23 March 2020
(This article belongs to the Special Issue Microstructure and Properties of Metallic Heat-Affected Zones)
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. View Full-Text
Keywords: laser surface alloying (LSA); ceramic coatings on Al alloy; microstructure; laser melted/heat affected zone (LMZ/HAZ); microhardness; wear; corrosion laser surface alloying (LSA); ceramic coatings on Al alloy; microstructure; laser melted/heat affected zone (LMZ/HAZ); microhardness; wear; corrosion
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Ravnikar, D.; Trdan, U.; Nagode, A.; Šturm, R. Energy Density Effect of Laser Alloyed TiB2/TiC/Al Composite Coatings on LMZ/HAZ, Mechanical and Corrosion Properties. Metals 2020, 10, 411.

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