Typically nozzles are made of brass, and these are the nozzles that ship with the printer. Brass offers excellent thermal characteristics; it heats quickly and maintains temperature well while transferring heat. This makes it efficient. It's also cheap and easy to produce. It suffers however from being very soft and wears easily, even “soft” filaments like white PLA which contains lots of pigments including titanium will wear the nozzle quickly. Still, considering how cheap brass nozzles are, given the excellent characteristics it's still often preferred to use brass nozzles even with mildly abrasive filaments and replace them after a print or three if you seldom use abrasive materials. Glass fiber filaments are capable of destroying a brass nozzle almost instantly.

Wear and hardness are directly related. The harder the nozzle the more resistant it will be to wear.

Higher thermal conductivity is better. It's ability to conduct heat determines how quickly the nozzle can heat up, and how easy to is to maintain temperature. The nozzle's thermal conductivity controls its ability to transfer heat to the filament evenly and quickly flowing through it.

All nozzles wear no matter what they are made of, the question is how hard are they compared to the extruded material and flow pressure which determines how quickly it wears.

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Anything over time will abrade what it flows through, this is how water carves through rock and mountains, and it's less abrasive than plastic. While wear is inevitable, some materials and additives are more abrasive than others.

Certain pigments are more abrasive:

• titanium used to make white
• strontium used in glow in the dark filaments

• wood
• carbon fiber
• glass fiber
• metals
• ceramics

Mohs hardness: 3.0 W/m K: 109 Cost: $1

Already discussed above. Not recommended for any abrasive filaments.

Mohs: 4 / 6 W/m K: 8.7/ 14 Cost: $2

Poor thermal characteristics. Wears better (slower) than brass and cheap.

Mohs: 7.5 W/m K: 41 Cost: $4

Higher carbon content in the steel increases the hardness and allows further heat treatment and tempering which also increases hardness.

Worse thermal characteristics than Steel. Wears better than Steel. Good for Carbon fiber and glass fiber filled materials.

Cost: $7

Mohs: 9.0 W/m K: 110 Cost: $29

Very good overall.

Mohs: 9.5 W/m K: 120 Cost: $29

Best overall balance with excellent hardness and thermal conductivity while balancing

Mohs: 9.0 W/m K: 35 Cost: $19

Balances cost. Often considered “fragile”, if the nozzle hits hard metal can crack, though not a natural problem for on the Neptune series. While ruby its is often considered a poor thermal conducer, it's normally coupled with bimetal brass or other materials which have great conductivity and it's not as much of an issue because its only the very thin tip that's ruby.

Mohs: 10.0 W/m K: 1500 Cost: $50 - $95

Hardest substance overall means incredible wear resistance. Thermal conductivity off the scale. However the most expensive. Yet not likely to need replacement,