Solutions for Critical Raw Materials under Extreme Conditions: A Review

Abstract

In Europe, many technologies with high socio-economic benefits face materials requirements that are often affected by demand-supply disruption. This paper offers an overview of critical raw materials in high value alloys and metal-matrix composites used in critical applications, such as energy, transportation and machinery manufacturing associated with extreme working conditions in terms of temperature, loading, friction, wear and corrosion. The goal is to provide perspectives about the reduction and/or substitution of selected critical raw materials: Co, W, Cr, Nb and Mg.

Keywords: alloys; chromium; cobalt; composites; critical raw materials; extreme conditions; magnesium; niobium; substitution; tungsten.

Figure 1

List of critical raw materials (CRMs) for the EU. Elements in the pink box are the 20 considered as most critical (reprinted from [2]).

Figure 2

Ashby diagrams for different materials. (a) Young’s modulus vs. strength, (b) wear-rate constant vs. hardness. The blue rectangle highlights the WC cemented carbides (reprinted with the permission of Michael F. Ashby [13]).

Figure 3

Schematic representation of ceramic thermal barrier coatings. TBC, thermal barrier coating.

Figure 4

SEM image of the NiCoCrAlY bonding coat/Y₂O₃-ZrO₂ coating (reprinted from [69]).

Figure 5

Oxidation behavior of Fe-16Cr-16Ni alloy in comparison with Type 304 alloy, alloys with Si + Al additions (Group A) and alloys with only Si additions (Group B) (adapted from [73] with permission of Springer).

Figure 6

Fe-Cr-Al oxide dispersion strengthening (ODS) (KANTHAL©) currently produced or previously investigated at SANDVIK for very high temperature, 900–1350 °C (credit SANDVIK). The comparison from sagging test between a KANTHAL© ODS and a Fe35Ni25Cr superalloy after 2300 h at 1100 °C in carburizing atmosphere shows greater damage (oxidation and creep) rate in the superalloy. RSPM stands for rapid solidification powder, RE stands for rare earths and HT stands for high temperature (reprinted from [76], with permission of Bo Jönsson and with permission of Springer).

Figure 7

Potentiodynamic scans in 10% H₂SO₄ at 25 °C of Fe-40Cr alloy in comparison to an alloy where Cr is partially substituted by Al (Fe-35Cr-5Al) and the other two alloys where both are modified by micro-addition of Ru (0.2%) (reprinted from [75] with permission of Elsevier).

Figure 8

Polarization curves of untreated (000) and plasma nitrided (420, 500 and 460, where the number indicates the temperature of the nitriding process) 410 stainless steel in 3.5 wt % NaCl water solution (un-deaerated, unstirred) (adapted from [85] with permission of Elsevier).

Figure 9

Comparison of corrosion resistance of Al-Li alloys with 2000 and 7000 series alloys. (reprinted with the permission of Tolga Dursun [39] and with permission of Elsevier).