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:Under certain conditions.

[Anonymous Coward]

Reading the TFA, the authors compare the 3-D printed material with a cast and a wrought version.

Evidently the printed material is about 3 times (Yield Strength: 590 MPa / 86 ksi vs 160 MPa / 23 ksi) stronger than the reference casting.
But steel castings are KNOWN to be porous, full of inclusions and very low strength. They are, however, cheap.

It is an improvement on the wrought (YTS 590MPa vs 365 MPa & UTS 700 MPa vs 555 MPa & similar elongation)

High strength it is not. The aerospace industry will start to get interested when the Ultimate Strength approaches existing stainless materials (160 ksi / 1.1 GPa).

There is no mention of fatigue properties in the conclusions.

Is the process robust? Can it be replicated often with little change in the properties?

This is another step in the right direction and will open a number of useful applications.

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.