316L vs 17-4PH Steel Heatblock - Toolhead

With most SLM providers you can choose to get either 316L or 17-4PH steel. Some people in the past have gone with 17-4PH heatblock, but we decided to go in a different direction, selecting 316L instead. This might seem odd, considering that 316L has a ~10% lower thermal conductivity, and steel is already at a disadvantage in this regard compared to aluminum or copper.

Three factors support this decision:

• 17-4PH is extremely rigid and strong. This might seem like a good thing, but some people have reported issues with TC nozzles shearing the threads after thermal cycling, because the low ductility of the heatblock can't compensate for the differential expansion caused by the CTE mismatch. 316L instead is much more ductile, which makes it compliant enough to not have to worry about that
• 17-4PH stiffness and strength make it much harder to post process, increasing the risk of damaging something during the required tapping
• 316L is much cheaper, less than half the price of 17-4PH from some manufactures

EDIT 09/09/2025: Testing showed no issues with our material choice for the heatblock, but 316L can suffer cracking due to repeated thermal cycling. This means that in the future the heatblock might crack, in that case you can just swap it for a 17-4PH heatblock instead. If you get a heatblock keep this in mind: 316L is a very good choice for rapid prototyping, but 17-4PH might be a better choice for long term deployment. Remember that the Monolith toolhead is still in development and further changes will come in the future.