========== Gears and chains
They use rounded contacts between the teeth, and need excellent wear resistance and friction: gears should try amorphous alloys, especially Medalium N1
. Ams mentions that already. N1 can be a layer or solid.
Only the low heat conduction is unfavorable, but the lubricant removes the heat usually.Transmission chains
need similar properties.
========== Plain bearings
As they report good friction properties, amorphous alloys might make plain bearings
too, again as a layer or solid.
The low heat conduction is unfavorable but some uses don't need it. At cranes and other heavy machines, some joints move very slowly and briefly but would benefit from a higher contact pressure.
Bronze or polymer plain bearings are often sintered roughly from a powder to be porous
and carry oil, grease, graphite, MoS2
, Ptfe and more. A powder fits nicely the quick cooling needed by amorphous alloys.
I vaguely suppose that extreme hardness isn't desired, and that the mating faces should be ground after sintering, possibly in a preferred direction.
========== Fast rotations
Some machines rotate with big azimuthal (linear) speed
. Steam and gas turbines
do because their working fluid is fast and reacts to the linear speed. Water turbines
are slower but they pay for strong alloys too.
The shape of the parts matters and answers many demanding desires, while the material multiplies the break speed by (σ/ρ)0.5
: yield strength over density. This figure-of-merit is the azimuthal speed that breaks a thin ring. (2σ/ρ)0.5
breaks a uniform radial rod, thin blades held by a thick shaft achieve a bigger multiple of (σ/ρ)0.5
. | Z1 T1 N1 | CrNiMo12 Ti-662 18-12-5 Carbon
σ MPa | 1700 ≈2000 ≈3000 | 800 1100 2400 ≈1400
ρ kg/m3 | 6620 5900 8500 | 7700 4540 8083 1550
m/s | 507 ≈582 ≈594 | 322 492 545 ≈950
CrNiMo12 is the 1.4938 for steam turbines, 18-12-5 is a NiCoMoTi maraging steel, and "Carbon" a composite of strands laid in optimized directions.
* Against creeping, high- and low-pressure turbine stages will retain Ni and TiAl alloys.
* Turboprop have already graphite fans with metal protection at the leading edge.
* They use Ti alloys to resist bird impact: turbofans could have fans and early compressor stages of amorphous alloys
. Impact strength matters, pure strength and density too. Especially Medalium T1 could outperform present Ti alloys.
* Pressured-water reactors provide saturated steam at ≈280°C that condenses partially in the HP turbine. Docs don't tell how much they creep, but amorphous alloys at steam turbine blades might better resist eroding water droplets
that cost downtime, inspections, replacement.
* Sand in water erodes dams blades, corrosion does the rest, costing maintenance too. Amorphous alloys might make better dam turbines
when big parts become possible.
========== Strength and low conductivity
Some heavy aggregates must leak little heat: a boiler, a cold detector at a telescope, etc. Once the design uses only tensile and compressive wires, rods and tubes, a material's figure-of-merit σ/K remains, strength over heat conductivity, and amorphous alloys are good for both. A few uses need a low electric conductivity instead. | N1 | Ti-Al6V4 17-7 PH Glass Aramide
σ MPa | ≈3000 | 830 2300 550 >2000
K W/m/K | ≈10 | 6.6 16 0.5 0.05
C MS/m | 0.63 | 0.59 1.2 0 0
σ/K | 300M | 126M 144M 1.1G 40G
σ/C | 4.8k | 1.4k 1.9k - -
The spring stainless steel 17-7 PH exists as wires and strips that could make tubes. "Glass" is a composite of glass fibre strands, 550MPa its compressive strength. Aramide composites resist little compression, data is for unimpregnated strands under tension only. Pbo, Lcp might be even better.
Suspending an aggregate with polymer strands or glass fibre tubes is uneasy. Amorphous alloys are the best metals to hold and insulate an aggregate
I proposed to zap a wire to discard parts no longer needed, there scienceforums
Amorphous alloys excel at all aspects. A D=0.5mm L=10mm wire of Medalium T1 holds ≈400N, <3J zap it while air loses <2.5W and conduction <1W so 0.5s×0.9V×11A suffice, provided by one common 1g supercapacitor or an NiCd accumulator. Or zap faster with an alu capacitor.
At other alloys too, when electrons conduct little heat, the matrix matters much. So I propose to replace a good part of Nb and Zr by Ta and Hf when amorphous alloys shall conduct less heat
Marc Schaefer, aka Enthalpy