Practical 3D Printing: Metal Powders & Microstructures

Back to course

Watch This Course

$199 USD $99.50 USD

-OR-

Or 8 easy payments of only $12.44 USD Instant access. Easy checkout. No fees. Learn more

Enroll Now
8 easy payments of only $12.44 USD

Course Access for Life

60 day money back guarantee

Metal Powders & Microstructures

05.31

00:00	In this module we'll dive a little deeper into the details of the metal powder and the properties of the resulting final parts.
00:06	The powder itself is extremely fine and the first thing that needs to be mentioned here is that it poses some serious health risks should it get in someone's eyes, open wounds or be inhaled.
00:18	The operator handling the powder should wear a respirator and face covering at a minimum, although most will also wear gloves and overalls.
00:27	Each particle could be around 100 microns or 0.1 of a mm in diameter for the coarse powders and down to around 15 microns for the finer powders.
00:38	For reference, a human hair is around 70 microns in diameter so you can get an idea of the scale.
00:44	The size of the particles will be determined by the printer that's being used and each printer will have a size range it's designed to work with.
00:52	Generally, speaking, smaller particles are better as they pack together more tightly to minimize voids and they also flow better.
01:00	Think about pouring out a bucket of sand compared to pebbles.
01:04	The sand will flow easier and more smoothly.
01:07	With that said, excessively small particles can clump together so there is a balance that needs to be struck.
01:14	More consistent particle size helps ensure the powder is distributed evenly and this leads to more consistency in the properties of the final part.
01:23	More spherical particles are also better.
01:26	Again, this allows them to pack together more tightly and also flow better.
01:30	Imagine moving your hand through a bucket of ball bearings compared to oddly shaped rocks.
01:35	Higher quality powders will have more consistently sized and more spherical particles and often be finer.
01:42	Using these high quality powders will no doubt add cost to our parts but should also lead to better results.
01:49	Anything past this basic understanding is outside the scope of this course and not really helpful for us using magnets.
02:18	So, what exactly does this mean? As the powder is fused and the molten metal solidifies, crystalline areas, which are also known as grains, are formed to make up the inner structure of the metal part.
02:31	This is a very detailed topic and again outside the scope of this course.
02:36	But the size, shape and orientation of these grains are primarily influenced by the manufacturing process and have a huge impact on the properties of the part like ultimate strength and the fatigue limit.
02:48	Fatigue is a common cause of failure in automotive parts and occurs when a part is repeatedly loaded in small cracks and the cracks continuously grow weakening the part and eventually failing altogether.
03:00	This happens even when the loads are much lower than the ultimate load that the part can handle.
03:05	Any defects in the surface or structure of the part or even sharp internal corners in the design can concentrate stress and cause fatigue cracks.
03:14	How does this apply to us? 3d printing metal typically leads to a grain structure that causes anisotropy in the mechanical properties.
03:24	Anisotropy being the opposite of isotropy means that the part will be stronger in one direction compared to another.
03:31	Although the difference here won't be anything like the difference with FDM parts.
03:36	What's more of an issue is the density of the part as well as internal voids and surface defects.
03:41	The more these defects can be reduced by the use of quality powder and printing processes, the stronger the part will be.
03:49	All other things like part geometry being equal of course.
03:52	But at this stage in the development of the technology, a maximum of only 98% of the density of a cast part can be achieved.
04:01	Simply put, this means the microstructure of 3D printed metal parts and therefore the strength still falls short of cast parts, which is generally less than machined billets parts, which is generally less than forged parts.
04:14	However, this is the price that we pay for the manufacturing flexibility.
04:18	Heat treatment post-processors are an effective way of changing the microstructure.
04:22	Of the part and therefore their properties.
04:25	Although this of course comes at an extra cost.
04:28	When we see the letters like T5 or T6 after the material name, this indicates the heat treatment that has been used.
04:36	Depending on the material and heat treatment used, these processes can be used to improve the thermal and electrical conductivity, corrosion resistance, surface hardness, strength and ductility.
04:47	As you might have guessed, this is a complex and lengthy topic.
04:51	So, we'll leave it at that for this course.
04:53	Before moving on to discuss the specific materials that we can use for metal 3D printing, let's summarize this module.
04:59	The attributes of the powder have an impact on the quality of the print.
05:03	And while we won't typically need to concern ourselves with this when using manufacturing services, this does have a lead-on effect to the microstructure of the part and therefore its properties.
05:14	Compared to alternative production processes like forging, billet machining and casting, the strength and fatigue resistance, of 3D printed parts does fall short, but only just and this is something that's improving over time.