Investment casting works with almost any alloy that can be melted and poured, and in industrial practice the choice narrows to ten families: four steel families, three high-temperature families, plus aluminum, copper and precious metals. What separates them is not whether the process can handle them, but how much of the answer the governing specification gives you.
For steel and alloy parts, investment casting is not a separate metallurgical world. ASTM A957 (general industrial use) and A985 (pressure-containing parts) are general-requirements specifications laid over the same grade specifications a sand foundry pours to — A216, A351, A743, A958 and the rest. The grade you name does not change; what changes is the section you can hold.
| Material Type | Common Grades / Examples | Key Characteristics | Typical Applications |
|---|---|---|---|
| Stainless steel | 304, 316, 17-4 PH, 15-5 PH | Corrosion resistance, strength | Valves, pumps, food equipment, marine parts |
| Carbon steel | WCB-type alloys, 1020/1045 equivalents | Good strength, low cost | Machinery, brackets, construction components |
| Low-alloy steel | 4140, 4340 equivalents | High strength and wear resistance | Automotive and industrial components |
| Tool steel | H13, D2-type alloys | Hardness, wear and heat resistance | Tools, dies, wear components |
| Nickel-based alloys | Inconel 625, Inconel 718, Hastelloy | Excellent high-temperature and corrosion resistance | Aerospace, turbines, chemical equipment |
| Cobalt-based alloys | Stellite-type alloys | Wear, corrosion and heat resistance | Turbine parts, valves, medical components |
| Aluminum alloys | A356, 356, 6061-type compositions | Lightweight, corrosion resistant | Aerospace, electronics, automotive parts |
| Copper alloys | Bronze, brass | Conductivity, corrosion resistance | Marine hardware, electrical and decorative parts |
| Titanium alloys | Ti-6Al-4V | Very high strength-to-weight ratio | Aerospace, medical implants |
| Precious metals | Gold, silver, platinum | Appearance, corrosion resistance | Jewelry, dental and specialty components |
1. Stainless Steel
Cast stainless steel is ordered under ACI designations, not the wrought numbers on the drawing: 304 becomes CF8, 316 becomes CF8M, 17-4 PH becomes CB7Cu-1. The cast compositions differ from their wrought counterparts by intent, which is why ASTM adopted the ACI names for castings and why writing “316” on a casting purchase order leaves the grade undefined.
| ACI grade (UNS) | Wrought analogue | Min tensile | Min yield | Min elongation |
|---|---|---|---|---|
| CF8 (J92600) | 304 | 70 ksi (485 MPa) | 30 ksi (205 MPa) | 35 % |
| CF8M (J92900) | 316 | 70 ksi (485 MPa) | 30 ksi (205 MPa) | 30 % |
| CF3 (J92500) | 304L | 70 ksi (485 MPa) | 30 ksi (205 MPa) | 35 % |
| CF3M (J92800) | 316L | 70 ksi (485 MPa) | 30 ksi (205 MPa) | 30 % |
| CA15 (J91150) | 410 | 90 ksi (620 MPa) | 65 ksi (450 MPa) | 18 % |
| CA6NM (J91540) | — | 110 ksi (755 MPa) | 80 ksi (550 MPa) | 15 % |
| CB7Cu-1 (J92180), H900 | 17-4 PH | 170 ksi (1170 MPa) | 145 ksi (1000 MPa) | 5 % |
| CB7Cu-2 (J92110), H900 | 15-5 PH | 170 ksi (1170 MPa) | 145 ksi (1000 MPa) | 5 % |
The corrosion-resistant grades come from A743, the precipitation-hardening ones from A747. Expect a CF-grade casting to be magnetic: cast CF alloys are duplex ferrite-in-austenite, typically 5 to 40 % ferrite, where the wrought equivalent is fully austenitic.
Two specification catches are worth settling before the order goes out. Ordering CF8 as low-ferrite or non-magnetic drops its guaranteed minimums to 65 ksi (450 MPa) tensile and 28 ksi (195 MPa) yield. And in A747 the entire mechanical property table is supplementary unless the customer stipulates it — a PO naming CB7Cu-1 in the H1025 condition, without invoking the mechanical requirements, has not bought 150 ksi.
2. Carbon Steel
Carbon steel castings are the low-cost end of the range, and they can be ordered two ways: to a general steel casting specification such as A216 or A27, or to A732, which was written specifically for carbon and low-alloy steel castings made by the investment process.
WCB is the default for pressure-containing parts, at 70 to 95 ksi (485 to 655 MPa) tensile and 36 ksi (250 MPa) minimum yield. Read that tensile figure as a range rather than a floor — an over-strength heat is out of specification the same way a weak one is, which catches buyers who assume more strength is always acceptable.
A732 carries its own ladder for investment castings, from grade 1A annealed at 60 ksi (414 MPa) tensile and 40 ksi (276 MPa) yield to grade 3Q, quenched and tempered, at 100 ksi (689 MPa) and 90 ksi (621 MPa). For a structural part rather than a pressure part, ordering to A732 keeps the acceptance criteria inside a document written around this process.
When welding or machining downstream has to match a wrought component, A915 and A958 list cast grades carrying wrought chemistry — SC 1020 through SC 1045 — so the analysis on the MTR lines up with the mating part.
3. Low-Alloy Steel
4140 and 4340 do exist as cast grades, SC 4140 and SC 4340 under ASTM A958, but naming the grade buys no strength on its own. A958 separates chemistry from properties: you order a grade and a strength class, and not every grade is marked suitable for every class.
| Cast grade (UNS) | Wrought analogue | Highest class marked suitable |
|---|---|---|
| SC 4130 (J13502) | 4130 | 135/125 |
| SC 4140 (J14045) | 4140 | 165/150 |
| SC 4330 (J23259) | 4330 | 210/180 |
| SC 4340 (J24053) | 4340 | 210/180 |
Class 210/180 means 210 ksi (1450 MPa) tensile and 180 ksi (1240 MPa) yield at 4 % elongation.
Two footnotes attached to that class table decide real parts. Heat treatment does not imply that every section thickness is through hardened, so a heavy section can meet the chemistry and still miss the class. And the specification warns that grades running far above the class minimum may be unsuitable because of weldability and machinability — specifying SC 4340 for a bracket that will be welded has a bill attached.
The investment-specific route again runs through A732, whose quenched-and-tempered grade 8Q is set at 180 ksi (1241 MPa) tensile and 145 ksi (1000 MPa) yield.
4. Tool Steel
Cast tool steel is bought to chemistry, not to hardness. ASTM A597 designates its grades by composition alone — CH-13 and CH-12 for the hot-work compositions, CD-2 as the cast D2 analogue — and the specification carries no tensile, yield, elongation or hardness requirement anywhere.
A chemistry-only specification puts the property you actually want on your own order. CH-13 gives you hot-work chemistry and nothing more; the working hardness comes from an austenitize-and-temper cycle you have to write into the purchase order, along with where hardness is measured and to what range.
The reason to cast the shape at all is that it arrives near net. A die block or wear component machined from hardened wrought stock spends its cost in the machine shop, and investment casting moves that cost into the pattern.
5. Nickel-Based Alloys
Two different industries sit under this heading, and only one of them has an ASTM casting specification behind it. A494 covers nickel and nickel-alloy castings for corrosion-resistant service — CW6MC is cast alloy 625, at 70 ksi (485 MPa) tensile and 40 ksi (275 MPa) yield, alongside the cast Hastelloy and Monel types. For heat-resisting work there is A560, whose 50Cr-50Ni castings are intended for corrosive environments up to 2000 °F (1090 °C).
Alloy 718 does not appear in A494 at all, and neither do the directionally solidified or single-crystal blade alloys. Those alloys are ordered to AMS and proprietary specifications and cast in furnaces built for controlled solidification. If your print says 718, you are not buying from the same specification system or the same supplier base as the chemical-service castings above it.
6. Cobalt-Based Alloys
Cobalt alloys are written into the investment casting specification itself: A732 covers carbon and low-alloy castings and, in the same document, cobalt alloy for high strength at elevated temperatures, in grades 21 and 31, both supplied as cast.
How they are accepted tells you what they are for. Neither grade carries a room-temperature tensile or yield minimum. Grade 21 is qualified at 1500 °F (820 °C) — 52.0 ksi (360 MPa) tensile and a 23.0 ksi (160 MPa) stress rupture minimum with a 15-hour rupture life.
A specification that only tests hot is describing valve trim, turbine hardware and wear faces that live at temperature. These are surface-life alloys rather than structural ones.
7. Aluminum Alloys
Aluminum investment castings are ordered to ASTM B618, and the usable alloy set is narrower than the general aluminum casting market. Casting alloys are registered in their own xxx.0 series, separate from the four-digit wrought designations, so a “6061 casting” does not exist as a registered alloy — 6061 is a wrought designation only.
The reason to specify aluminum is specific strength, not strength. A published study of cast A356 puts T6 tensile strength around 330 MPa against 485 to 655 MPa for a WCB carbon steel casting, and notes that achieved properties vary significantly with cooling rate and dendrite arm spacing. The aluminum part wins on mass, and only on mass.
8. Copper-Based Alloys
Copper alloys are investment cast for marine hardware, electrical parts and bearing surfaces, but no dedicated ASTM investment-casting specification exists for them. B824 sets general requirements across the copper casting standards — sand, permanent mold, die, centrifugal, continuous — and none of the documents it governs is an investment casting document, so an investment-cast bronze is typically ordered to a specification such as B584, written for sand castings, with the process stated separately.
Having no investment-specific standard shapes what gets tested. B824 mandates chemical composition, tensile and yield strength, hardness and elongation, plus electrical resistivity and conductivity — on a copper casting, conductivity is a specified and tested property rather than something the alloy family hands you.
9. Titanium Alloys
Titanium is investment cast only in a melt shop built for reactive metals. ASTM B367 requires melting by the processes used for reactive metals, and castings are supplied as cast, with heat treatment limited to stress relief where weld repair is involved. C-5 is the Ti-6Al-4V casting grade.
The mold is the other half of the problem. Molten titanium reduces oxide refractories, leaving an oxygen-enriched, brittle surface layer — alpha case — that has to be machined or chemically milled away before the part is usable. A 2025 study measured roughly 350 µm of alpha case on commercially pure titanium cast into alumina-based molds. Those are laboratory melts, but the order of magnitude is why titanium work stays with specialist foundries running their own face coats.
10. Precious Metals
Precious metal casting is the same lost-wax principle running in a different kind of shop. Gold, silver and platinum are cast in flasks rather than ceramic shells, in small melts.
The economics run the other way round from industrial casting. Metal value dominates the cost of the part, so sprue, scrap and grinding dust are recovered and remelted, and the plant is organized around metal accountability rather than around machining hours. It is a different business with different equipment, not a variation on an industrial foundry.
How to Choose an Investment Casting Material
Choose the specification first and the alloy name second, because the family name guarantees nothing by itself. Within stainless alone, minimum yield strength runs from 30 ksi for CF8M to 145 ksi for CB7Cu-1 in the H900 condition — nearly a fivefold spread across grades that all get called stainless on a drawing.
- Name the failure mode: corrosion, static strength, wear, or temperature. That narrows the family faster than any comparison table.
- Find the grade specification that governs it: then use the cast designation on the order — CF8M rather than 316, SC 4140 rather than 4140.
- Check what that specification actually guarantees: chemistry only, as in A597 tool steel; mechanicals that stay supplementary until you invoke them, as in A747; acceptance at temperature only, as for the A732 cobalt grades; or a grade and a strength class you must order both halves of, as in A958.
- Add the investment casting general requirements: A957 for general industrial steel and alloy castings, A985 for pressure-containing parts. They ride on top of the grade specification rather than replacing it.
- Confirm the family has a supplier base you can reach: reactive metals need a dedicated melt shop, single-crystal nickel needs controlled-solidification furnaces, and precious metals are cast in another industry altogether.
For most industrial parts the decision ends inside the four steel families, which is also where the specification system is most complete — grade, class, heat treatment and acceptance are all written down, so the risk sits in ordering precisely rather than in guessing.