Practical 3D Printing: Materials

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Materials

09.51

00:00	In the previous two modules we've focused on the considerations around materials for additive manufacturing of metals.
00:06	However, we haven't yet covered the specific materials that can be printed.
00:10	There are lots of options available for manufacturing services, and the properties and strengths of these will be listed on the provider's website to help us choose between them.
00:20	The reality is that covering every single material option available and all the metallurgy behind the differences in properties would take a very long time.
00:29	So, with that in mind, in this module we'll cover the options we have, but we'll limit further discussions to materials we're actually interested in for automotive projects, and provide some examples of where you might use each material on a race car.
00:43	Most of these materials are alloys.
00:45	So, for clarity, before we begin, an alloy is a material composed of two or more elements, one of which must be metallic.
00:54	The term alloy is commonly misused as a synonym for aluminium.
00:58	Clearly, pure aluminium isn't an alloy.
01:01	But there are aluminium alloys, and these are predominantly aluminium.
01:05	Usually, over 90%, with small amounts of alloying materials.
01:10	On that note, we'll start with aluminium, which is well suited to performance applications, thanks to its high strength to weight ratio and corrosion resistance.
01:19	It's also relatively cheap and easy to work with as far as metals go, so often used for machined parts.
01:25	The aluminium alloys we use in additive manufacturing are much like those used in billet parts, with major alloying elements of magnesium for extra strength, and silicon which lowers the melting temperature, helping with manufacturing processes like SLM where we melt the material.
01:43	AL-SI10MG has approximately 90% aluminium, 9% silicon, and 1% magnesium, and is a solid all-rounder for good mechanical and thermal properties, specifically the strength to weight ratio and stiffness.
01:59	It's ideal for structural components like housings, brackets, and linkages, as well as ducting, intake manifolds, and other plumbing.
02:07	This alloy tends to be used for motorsport parts, but AL-SI7MG 0.6 is an alternative that offers advantages in thermal conductivity, making it suitable for heat exchanger components like intercoolers.
02:22	Other alternatives are 6000 grade aluminium with improved strength, ductility, and surface finish, as well as 7000 grade, which has even higher mechanical properties and is commonly used for aircraft parts.
02:34	Moving on to steels, which of course are also alloys, this time containing iron, carbon, nickel, chromium, manganese, and so on.
02:42	Some low carbon steels, like maraging steels, can be printed for applications like tooling, but this is fairly uncommon for our projects, and these materials are very unlikely to find their way around.
02:53	More commonly used for car parts is stainless steel, which we all know for its amazing strength, durability, and corrosion resistance, although not being as light as aluminium.
03:04	There are a few different grades of stainless steel available for 3D printing that we'd be interested in.
03:10	One of these is 316L, which is commonly called marine grade stainless steel thanks to its excellent corrosion resistance.
03:17	This is suitable for anything exposed to the elements on the exterior of the vehicle, such as carbon fiber, aluminum, aluminum, and other materials.
03:25	For more strength and mechanically demanding applications, we'll use 630 grade stainless steel, which is more commonly called 17-4 pH in the additive manufacturing space.
03:37	15-5 pH is another modification of this, with slightly better stability at higher temperatures.
03:43	Either are great options for applications where the strength of aluminium isn't sufficient, although of course this comes with a weight penalty.
03:51	Good examples of where you'd use these would be in engine components or turbo manifolds.
03:56	Next, we get into the more exotic material of titanium.
03:59	As usual for additive manufacturing, these are all alloys.
04:03	This is where we really start to see the benefits of additive manufacturing, making these expensive materials more accessible and processable.
04:13	Titanium has a better strength to weight ratio than stainless steel and even aluminium.
04:18	For the same strength, a titanium part will typically weigh around 40 percent of the equivalent stainless part.
04:24	It has better corrosion and chemical resistance than stainless, so the parts remain in good condition for longer.
04:30	However, with that said, titanium isn't nearly as durable as stainless.
04:35	It's much softer and more susceptible to dents and wear from abrasive conditions.
04:40	The different grades of titanium are a lot easier to understand though, as they're generally named grade 1, 2, 3 and so on, and these go all the way up to grade 38.
04:51	These all have different positions of alloying elements and have received different degrees of post-processing.
04:57	Grade 1 is the softest and most ductile and is commonly used in motorsport, but not anywhere near as common as grade 5, which is also known as Ti-6Al-4V or titanium -64 or 6-4, and boasts considerably better mechanical properties.
05:14	What's important to understand in an area that we often see a lot of confusion around is the use of titanium in high -temperature builds like exhausts.
05:24	Titanium has a low thermal conductivity and high melting temperature, which makes it appealing for high-temperature use.
05:31	However, it actually breaks down at a much lower temperature than stainless.
05:35	After long amounts of time exposed to elevated temperature, it becomes very brittle and starts to crack or fracture.
05:42	So, while it might be suitable for applications like exhausts on higher-end motorsport builds where the weight saving justifies the shorter service life, it's not ideal for street cars or more budget-restricted race cars.
05:56	That's not to say it can't be used with success though, especially when the temperatures aren't as severe.
06:02	Grade 23 is similar to grade 5 and it's also called Ti-6Al-4V, although with very important following letters of Eli, standing for extra-low interstitial.
06:14	Put simply, this means the oxygen and iron content are reduced, improving ductility and fracture toughness, helping to reduce the issues that we just discussed.
06:24	With all of this said, titanium is still used in valve trains and other engine components like connecting rods, although most commonly in naturally -aspirated applications where the temperatures are generally lower.
06:36	Anything past this is more suited to structural and suspension applications, with 3D printed titanium even seeing the use in wheels like HRE's 3D Plus.
06:46	Its extra expense is generally only justified by its use on larger parts, where the weight savings are more significant, although the savings for many smaller components like fasteners can add up when we're trying to shave every last gram.
07:00	Finally, we'll discuss nickel-based superalloys like Inconel.
07:04	Now, superalloy sounds very impressive, but what does that actually mean? A superalloy is able to operate at a very high fraction of its melting temperature, while maintaining a high fraction of its properties.
07:17	These include high mechanical strength, as well as extra-low thermal and corrosion resistance.
07:23	Inconel is ideal for extremely high -temperature applications around the engine like exhaust manifolds, turbo wheels, exhaust valves, or even battery contactors on EVs.
07:34	The two most common grades of Inconel for automotive use are 625 and 718.
07:40	Put simply, they both have great mechanical properties and thermal resistance, but 625 has better corrosion resistance and 718 is stronger.
07:51	718 would be the choice for an exhaust manifold, whereas 625 would be more suited to plumbing that conveys chemicals or a heat exchanger like an oil cooler.
08:00	With that said, realistically, EVA could be used with success in most applications.
08:05	What we've covered in this module have been the main materials available for SLM 3D printing that we'd consider for performance automotive projects.
08:14	There are many other metals that we can print, such as tungsten, copper, or cobalt chrome alloys, and the list is always getting longer.
08:22	While it's possible to use these in automotive projects, they lend themselves to very specific applications like copper -nickel fittings for plumbing our brake system.
08:31	In reality though, it's fairly unlikely that we'll be considering anything past what we're focused on, so let's recap this module before we move on.
08:40	There are many different metals available for 3D printing, but primarily of interest to us are aluminium alloys, stainless steel, titanium alloys, and super alloys like inconel.
08:52	All of these have relatively good corrosion resistance, at least for automotive applications anyway.
08:57	We look at aluminium alloys for their exceptional strength to weight ratio.
09:01	These materials are great for the likes of intake manifolds, casings and housings, structural brackets, and linkages.
09:07	When aluminium strength falls short, we'll usually look at stainless steels, particularly for exhaust components like turbo manifolds.
09:15	Titanium can seem appealing here, but it actually becomes brittle when exposed to excessive heat for extended periods.
09:22	It's more suited to structural components with higher stress than aluminium can handle, and where the weight advantage justifies the expense over stainless.
09:31	Inconel is a super alloy that maintains its strength at extremely high temperatures, and is really the gold standard for stress components near heat sources.
09:40	Again, if the cost is justified, this material is great for exhaust manifolds and engine or turbo components.