3D Printing Doubles the Strength of Stainless Steel (sciencemag.org)

sciencehabit writes: Researchers have come up with a way to 3D print tough and flexible stainless steel, an advance that could lead to faster and cheaper ways to make everything from rocket engines to parts for nuclear reactors and oil rigs. The team designed a computer-controlled process to not only create dense stainless steel layers, but to more tightly control the structure of their material from the nanoscale to micron scale. That allows the printer to build in tiny cell wall-like structures on each scale that prevent fractures and other common problems. Tests showed that under certain conditions the final 3D printed stainless steels were up to three times stronger than steels made by conventional techniques and yet still ductile.
The work was done using a commercially-available 3D printer, according to Science magazine. "That makes it likely that other groups will be able to quickly follow their lead to make a wide array of high-strength stainless steel parts for everything from fuel tanks in airplanes to pressure tubes in nuclear power plants."

Comments

Re: Metal and Plastic

[JaredOfEuropa]

Useful stuff is already being printed. Parts that are lighter and stronger than the ones they are replacing, and are more expensive or pretty much impossible to make by traditional methods (casting, machining). Obviously not very interesting for mass produced consumer goods (yet), but this is already being used in (petro)chemical process technology and military applications, and the aircraft industry is taking note as well. There are plenty of experiments in aircraft, at this time mostly with non structural parts where weight can be saved. The other day I saw some nice (and thoroughly weird looking) suspension arms for a low production volume sports car, printed in titanium.

Re: Metal and Plastic

[oic0]

Patents killed is mostly. It cost to much to do anything with the stuff because the patent holders were harsh. Isnt that great? if you think of something first, you can hold the whole human race back if you're a jerk.

Re: Metal and Plastic

[Anonymous Coward]

Even at a thousand times the cost of other methods, that would still be quite useful. Multiple projects I've worked on had a component that was struggling with multiple constraints, and spending a lot of money to make that part work saves money for the whole project. For example, we had a project where one part could be made using tradional methods, but would be larger due to give access to machine some required features and to have enough room to assemble with fasteners or welding. Making that part bigger meant other parts got larger, limiting what shops could make it, making transportation more difficult, etc, and would have ballooned the cost of the whole machine from $10M to $50M. Spending $500k to have the critical part 3d printed instead of $10k to be traditionally machined (not counting extra engineering required to make sure assembly worked) was a hell of a lot cheaper since the part was smaller. Even if we had to pay x1000 times as much, $10M for the part, it would have been cheaper than the extra $40M needed to make the rest of the machine accommodate a larger, more traditional part.

Re: Metal and Plastic

[MightyYar]

you can hold the whole human race back

Yeah, but not for long. And you set off a furious race to find workarounds, which itself often advances the state of the art.

There are exceptions... my hometown has a historically protected bridge. The reason it is historically protected is that it is a unique draw bridge design and I don't think there are any other surviving examples. The reason there are no other surviving examples is it is needlessly complex and thus prone to breakdown and relatively expensive to maintain. The reason it is needlessly complex is it had to work around a draw-bridge (Strauss and Scherzer bascule) patent and so used a Rall bascule design. This design was abandoned after the patent ran out. Because it sucked. Pretty soon the bridge will be 90 years old, and they are stuck with 90 years of extra maintenance and downtime because of the patent situation in 1930.

Re: Metal and Plastic

[Solandri]

Even at a thousand times the cost of other methods, that would still be quite useful.

While there are a myriad of factors which go into selecting the proper material for a design, the general criteria that steel is best at is strength per unit cost. If you can pay more, more exotic materials like titanium, tungsten, chromium, or amorphous ("glass") metals are stronger per unit volume than steel. If you need lighter weight, aluminum and magnesium tend to have more strength per unit mass. If you need temperature resistance, niobium, molybdenum tend to be better. etc.

That said, a 2-3x strength increase is just huge, and could upset some of the generalities I listed above. It's been a decade since I delved into materials science, but a 2-3x stronger steel could displace both glass metals for strength per volume, and aluminum for strength per weight.

The latter would have serious implications for the aerospace industry. The big drawback of aluminum (other than relatively low melting point, which isn't an issue in subsonic flight) is that it has a fatigue limit. With a steel structure, you can design it so that repeatedly flexing it no longer causes it to weaken. Aluminum has no such point - flexing it will always cause it to weaken (which is why it was stupid to make Curiosity's wheels out of aluminum). Fatigue failure of aluminum has been the cause of numerous airliner accidents, from the original de Havilland Comet, to Aloha 243, to JAL 123 (greatest loss of life from a single aircraft accident). It's why pressurized airframes are retired and destroyed after about 75,000-100,000 flights. If 3D printed steel has a higher strength per weight than aluminum, it would revolutionize aircraft design.

Re: Metal and Plastic

[careysub]

Aluminum has no such point - flexing it will always cause it to weaken (which is why it was stupid to make Curiosity's wheels out of aluminum).

Reading the article and consulting NASA information about the Curiosity mission does not support the assertion that the wheel design was in any way "stupid".

According to the article you link to the (many) components of Curiosity were not tested to destruction but were tested a maximum of three times the expected mission life without failing. Curiosity was never intended to last "forever" but to last for its two year mission life which involved an 8 km trip to Aeolis Mons, its mission target. With a three-fold mission life testing program this suggests that the rover could be expected to last up to 6 years and travel 24 km before failures would likely end the mission, but anything over the original mission specification is gravy. Curiosity has now traveled 17.5 km.

Again, according to the article, what they have observed is cracks in two treads in one wheel. Test data indicates that when there are three cracked treads the wheel is at 60% of its service life. Currently there are only two, so it is at less than 60% of its service life. But let us suppose that it is at 60%, then it should be good for 29.2 km, i.e. for another 12 km, which is over three times the planned mission. But since it is only two treads, it should be more than that. What's more this is only in one wheel so far, and Curiosity can travel on five good wheels, so the service life limitation from wheel wear is likely to be quite substantially more than another 12 km. By then lots of other components will have exceeded their 3-fold mission life testing and be candidates for failure.

In short the wheels seem more than adequately spec'd and tested for the mission. It is unlikely that they will end up the cause of mission end, which in any case will be well more than three times the original planned mission. Putting 100 km wheels on Curiosity (for example) would simply have driven up cost, reduced the weight budget for some other items, all without meaningfully extending the mission potential life.