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For those who may be unaware: martensitic steels encompass all standard tool steels, e.g the ones used for knives, springs, dies, files etc. martensitic means h

For those who may be unaware: martensitic steels encompass all standard tool steels, e.g the ones used for knives, springs, dies, files etc. martensitic means hardenable. Being able to 3D print these into arbitrary shapes vs machining them will likely be of the most value for parts that need to be light. I’m curious that they mention wanting to print low alloy steels, since low alloy steels tend to be relatively easy to machine. I’d have expected more interest in higher performance steels. Can anyone comment why people would want to print in low-alloy martensitic steel? The article doesn’t address this, but, the martensitic transformation typically changes a part’s volume by ~4%. that can make it difficult to make precision parts unless final finishing happens at full hardness. I wonder if this process results in direct production of martensite, or if the parts still need heat treatment. To me, this is a very interesting process, but doubly so given the possibilities of generative design. For those who want to visualize why you might want to 3D print steels vs machining them, think more about brackets and support structures than turbines, and take a look at some generative design parts.

DelightOne 7y ago
Did they fix the problem with the bad surface properties which printing usually entails? I read an article a couple years ago on it.
- gumby 7y ago
  That might be one reason for going for these low alloy steels: machine the surface after printing for finish and any dimensional issues.
econcon 7y ago
Turbine blades, impellers, valves are good candidate for printing. Machining creates chips and I think you need to have variety of metal stock to spin on lathe, with different dimensions. So if you've simply a bucket of metal to form any shape you want, it might be favourable to avoid uncessary wastage, cleaning, or stocking. For example, in 3d printing plastic you just need a roll of plastic or pellets.
- abakker 7y ago
  Actually, I’d be surprised if any of those were good candidates. Turbine blades in jet engines aren’t even machined now - they are grown out of inconel. Valves are highly dependent on surface finish and frequently multi-material setups - e.g. o rings. Not to make light of matching costs, but in the scheme of getting a part made, even of tool steel, the overall contribution of the materials is usually not super high. Machine time, tool bits, and design work are all MUCH more costly.
  - c22 7y ago
    Huh, from the hangout and hack stuff all day at the maker space perspective this is flipped completely on its head. I have plenty of time to design things and operate machines, and even the cost of the machines (bits included) is shared to the point that it's almost free as an individual. It's waiting on those gosh darn materials budgets to appear that holds up all my projects.
    - abakker 7y ago
      I should clarify, in production projects, materials may end up being a much greater overall part of the process, especially if the production is heavily automated. However, 3D printing of tool steels seems like it is aimed at lower volume parts where the automation will be lower, so paying a machinist to load/unload, finish, debur etc might be a relatively larger portion of the time. For us hobbyists, the CAD time is free, so it tends to cost less :)
- manfredo 7y ago
  Modern turbine blades are mostly made out of nickel, not steel. They're cast in such a way that they form a single crystal structure [1]. This makes 3d printing a no-go. Also, turbine blades are moving to ceramic matrix composite construction [2]. 1. https://www.americanscientist.org/article/each-blade-a-single-crystal https://www.americanscientist.org/article/each-blade-a-singl... 2. https://en.wikipedia.org/wiki/Ceramic_matrix_composite https://en.wikipedia.org/wiki/Ceramic_matrix_composite
contingencies 7y ago
why you might want to 3D print steels 3D printing tool metal is an established approach which facilitates complicated internal structures that cannot be otherwise machined and has been experiencing strong growth in recent years. Such structures are critical for establishing precise thermal control during high energy applications which correspondingly enables greater accuracy by reducing part warpage during temperature change, exceptional cycle times and part lifetime in a range of production industries: polymer injection molding is a certainty, but this probably also has applications in weaponry, engine design and some other aspects of aerospace.
rsfern 7y ago
Martensite formation is just one specific hardening mechanism in steels. Other hardening mechanisms (work/deformation hardening, pearlite formation, precipitation hardening) aren’t really amenable to additive processes - what’s the point of 3D printing if you have to deform your part to get the strength or hardness you need? I read through the paper, and the as-printed parts are still fully martensitic, no post-heat-treatment needed. So the volume change is baked in at least. To me, where your last point gets super interesting is functionally graded materials, which at least some of this group of authors are working on as well. Basically you could figure out how to locally temper this martensitic steel as you print it, so that you get graded properties — strength and hardness where it’s needed, but ductility in other places. It’s sort of a pretty open research area still

DelightOne 7y ago

Did they fix the problem with the bad surface properties which printing usually entails? I read an article a couple years ago on it.

gumby 7y ago
That might be one reason for going for these low alloy steels: machine the surface after printing for finish and any dimensional issues.

econcon 7y ago

Turbine blades, impellers, valves are good candidate for printing. Machining creates chips and I think you need to have variety of metal stock to spin on lathe, with different dimensions. So if you've simply a bucket of metal to form any shape you want, it might be favourable to avoid uncessary wastage, cleaning, or stocking. For example, in 3d printing plastic you just need a roll of plastic or pellets.

abakker 7y ago
Actually, I’d be surprised if any of those were good candidates. Turbine blades in jet engines aren’t even machined now - they are grown out of inconel. Valves are highly dependent on surface finish and frequently multi-material setups - e.g. o rings. Not to make light of matching costs, but in the scheme of getting a part made, even of tool steel, the overall contribution of the materials is usually not super high. Machine time, tool bits, and design work are all MUCH more costly.
- c22 7y ago
  Huh, from the hangout and hack stuff all day at the maker space perspective this is flipped completely on its head. I have plenty of time to design things and operate machines, and even the cost of the machines (bits included) is shared to the point that it's almost free as an individual. It's waiting on those gosh darn materials budgets to appear that holds up all my projects.
  - abakker 7y ago
    I should clarify, in production projects, materials may end up being a much greater overall part of the process, especially if the production is heavily automated. However, 3D printing of tool steels seems like it is aimed at lower volume parts where the automation will be lower, so paying a machinist to load/unload, finish, debur etc might be a relatively larger portion of the time. For us hobbyists, the CAD time is free, so it tends to cost less :)
manfredo 7y ago
Modern turbine blades are mostly made out of nickel, not steel. They're cast in such a way that they form a single crystal structure [1]. This makes 3d printing a no-go. Also, turbine blades are moving to ceramic matrix composite construction [2]. 1. https://www.americanscientist.org/article/each-blade-a-single-crystal https://www.americanscientist.org/article/each-blade-a-singl... 2. https://en.wikipedia.org/wiki/Ceramic_matrix_composite https://en.wikipedia.org/wiki/Ceramic_matrix_composite

contingencies 7y ago

why you might want to 3D print steels 3D printing tool metal is an established approach which facilitates complicated internal structures that cannot be otherwise machined and has been experiencing strong growth in recent years. Such structures are critical for establishing precise thermal control during high energy applications which correspondingly enables greater accuracy by reducing part warpage during temperature change, exceptional cycle times and part lifetime in a range of production industries: polymer injection molding is a certainty, but this probably also has applications in weaponry, engine design and some other aspects of aerospace.

rsfern 7y ago

Martensite formation is just one specific hardening mechanism in steels. Other hardening mechanisms (work/deformation hardening, pearlite formation, precipitation hardening) aren’t really amenable to additive processes - what’s the point of 3D printing if you have to deform your part to get the strength or hardness you need? I read through the paper, and the as-printed parts are still fully martensitic, no post-heat-treatment needed. So the volume change is baked in at least. To me, where your last point gets super interesting is functionally graded materials, which at least some of this group of authors are working on as well. Basically you could figure out how to locally temper this martensitic steel as you print it, so that you get graded properties — strength and hardness where it’s needed, but ductility in other places. It’s sort of a pretty open research area still