Complex multi-component carboboride coating produced by laser cladding

• Grant number: 24/09722-3
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: March 01, 2025
• End date: July 31, 2027
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Walter José Botta Filho
• Grantee: Caio Lucas Gueiros Pedrosa Martins
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

Metallic glasses, materials with a non-crystalline structure, have exceptional properties, such as high mechanical strength and high resistance to corrosion and wear. However, such alloys exhibit structural relaxation, with transformation of the glass phase into crystalline phases, when exposed to temperatures as low as ~600 °C. Usually such phase transformation is accompanied by reduced mechanical properties and increased susceptibility to corrosion. An interesting approach involves the formation of crystals with a composition similar to that of the original glassy alloy, which are more thermally stable. This is the principle of so-called pseudo-high entropy alloys (PHEAs). Such alloys have a high tendency to form glass (GFF), and they first crystallize major multicomponent phases from the glass matrix, thus preserving corrosion resistance, with the benefit of also increasing mechanical properties. However, despite the interesting initial characteristics during crystallization, at prolonged temperatures and times, the multicomponent principal phases transform into borides, in a diffusional process characterized by high solute segregation and, therefore, loss of corrosion resistance. Recently, vitreous alloys have been developed that, when crystallized, result in complex multicomponent compounds with boron and carbon, Mx(B,C)y, which are extremely hard (Vickers hardness >1000 HV) and resistant to corrosion (corrosion current density, icorr, ~10-6 A/cm², passive grade stability >1000 mV) and wear (specific wear rate, , ~10-5 mm3/Nm), and highly thermally stable, being the equilibrium phase over a wide temperature range (ambient at ~1500 °C). The interest is to apply these new alloys as protective coatings. Laser cladding emerges as one of the most promising options due to its high cooling rate and accuracy. Therefore, in this research project it is proposed the development of materials based on metallic glasses, which are precursors for stable and complex final crystalline phases, for use as a coating to face severe environments.