Intermetallics as innovative CRM-free materials Pavel Novak1, Lucyna Jaworska2, Marcello Cabibbo3 1 Department of Metals and Corrosion Engineering, University of Chemistry and Technology Prague, Technická 5, 16628 Prague. Czech Republic; panovak@vscht.cz 2 The Institute of Advanced Manufacturing Technology, Wroclawska 37A, 30-011 Krakow. Poland 3 DIISM/Università Politecnica delle Marche, Via Brecce Bianche, 60131-Ancona, Italy

Outline Properties of intermetallics Presented applications of intermetallics High-temperature materials Tool materials Corrosion resistant materials Biomaterials Production of intermetallics

Properties of intermetallics High melting points High hardness High resistence against high-temperature oxidation Excellent corrosion resistance Aluminides and silicides = low density Shape memory Hydrogen storage ability Special magnetic or electric properties … x Low room-temperature ductility Problematic production

Presented applications of intermetallics Power generation Automotive industry Chemical industry Aerospace industry Medicine

High-temperature materials Heat-resistant steels, nickel alloys, cobalt alloys CRMs: Cr, Co, Nb, W Applications: Airplane jet engines Car combustion engines (turbocharger, exhaust valves) Furnace elements …

High-temperature materials Turbine blades of airplane engines (Boeing 787, 747) High-temperature oxidation (800°C, air) P. Novák, et al., Intermetallics 19 (2011) 1306-1312 http://www.moeller-aerospace.com/specialties/titanium-aluminide

High-temperature oxidation (800°C) Fe-Al-Si-Ni High-temperature oxidation (800°C) P. Novák, et al., Key Engineering Materials 465 (2011) 407-410.

Tool materials Cemented carbides, tool steels CRMs: Co, W, Cr, (Mo)

Intermetallics as tool materials? Hardness Wear resistance

Short fibre- reinforced NiAl-Al2O3 composites Particle- reinforced 1 wt. % 10 wt. % Short fibre- reinforced 1 wt. % 5 wt. % P. Novák, et al., Powder Metallurgy 54 (2011), 308-313

NiAl-Al2O3 composites P. Novák, et al., Powder Metallurgy 54 (2011), 308-313

Corrosion-resistant materials Stainless steels, nickel alloys Contain CRMs: Cr, (Mo) Applications: Chemical industry Car exhausts Kitchen tools Other aggressive environments

Corrosion-resistant materials Intermetallics based on Fe-Al system – passivation by Al2O3 at pH > 3 addition of Si – weaker passive layer at pH > 2 Intermetallics based on Ti-Al system – passivation by Al2O3 and TiO2 at pH > 2 addition of Si – less significant effect

Biomaterials Titanium alloys, cobalt alloys, stainless steels Contain CRMs: Nb, Co, Cr, (Mo)

Bone replacement material New Ti-Si based material Human bone

Production - Melting metallurgy high melting points (e.g. Ti5Si3 2130°C) high reactivity of the melts Ti-Al-Si alloy

Forming possible for intermetallics which exhibit plasticity at elevated temperatures (TiAl, NiTi) forming of Fe-Al a Fe-Al-C with the use of protective capsule I. Schindler et al. / Intermetallics 18 (2010) 745–747

TiAl-Ti5Si3 composite (MA + SPS) Powder metallurgy Powder preparation: melt atomization mechanical alloying Consolidation: HIP (hot isostatic pressing) SPS (Spark Plasma Sintering) Advantages – fine-grained structure Disadvantages – high costs, problematic sinterability of intermetallics TiAl-Ti5Si3 composite (MA + SPS)

Powder metalurgy - Mechanical alloying Joining of particles by plastic deformation Severe plastic deformation  structure refinement Formation of solid solutions and intermetallics Crushing of particles Usually long duration (10 – 100 h) Ultra-high energy mechanical alloying (1 - 4 h)

Powder metalurgy - Spark Plasma Sintering Spark Plasma Sintering (SPS) uni-axial pressing + high electric current ultra-rapid sintering conductive and non-conductive materials High Pressure SPS (HP SPS) up to 8 GPa lower porosity modified mechanical properties Ä. Knaislová, et al., Materials 10 (2017) 465

Self-propagating High-temperature Synthesis (SHS) TiAl-Ti5Si3 in-situ composite P. Novak et al., Powder Metallurgy 54 (2011) 50-55.

SHS - „Thermal explosion“ mode P. Novák et al., Powder Metallurgy 54 (2011) 50-55.

Conclusions Intermetallics are already substituting CRM-containing materials in selected applications (jet engines,...). For more wide use, the extensive development is needed. Positive reaction from industry required. Acknowledgement The international frame of the research was supported by COST Action CA15102.