Inconel vs Titanium for Machined Parts
Titanium wins on weight. Inconel wins on heat. Density, strength, service temperature, corrosion, machinability, and cost — compared with Inconel 718, Inconel 625, and Ti-6Al-4V data so the choice survives a design review.
IsoCNC Engineering Team
CNC Machining & DFM Engineers · Updated · 13 min read
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Quick Answer
Choose titanium (Ti-6Al-4V) when weight and room-temperature corrosion resistance lead the requirements — at 4.43 g/cm³ it is about 47% lighter than Inconel with a higher strength-to-weight ratio. Choose Inconel when the part must hold strength above ~400°C: Inconel 718 keeps working to ~700°C and Inconel 625 to ~980°C, where titanium softens and creeps. Inconel 718 also beats titanium on absolute strength (1,034–1,120 MPa yield vs 880–930 MPa) — but you will pay for it twice, in raw material and in some of the most punishing machining in the industry.
Two Premium Metals, Two Different Jobs
Titanium and Inconel both carry aerospace-grade price tags and reputations, but they were engineered for opposite problems. Titanium exists to be strong at the lowest possible weight — its 4.43 g/cm³ density delivers the best strength-to-weight ratio of any common structural metal. Inconel exists to keep working when it gets hot — it is a family of nickel-chromium superalloys that hold strength and resist oxidation from cryogenic temperatures up to 700°C (Inconel 718) or 980°C (Inconel 625). The decision is almost never about which is “better.” It is whether your part fights gravity or fights heat. This comparison uses the grades that actually appear on drawings: Ti-6Al-4V (Grade 5) on the titanium side, Inconel 718 and Inconel 625 on the superalloy side.
Inconel vs Titanium at a Glance
The three alloys that cover most machined-part drawings, with the numbers that drive the decision:
| Property | Ti-6Al-4V (Gr 5) | Inconel 718 | Inconel 625 |
|---|---|---|---|
| Density | 4.43 g/cm³ | 8.19 g/cm³ | 8.44 g/cm³ |
| Yield strength | 880–930 MPa | 1,034–1,120 MPa (aged) | 414–655 MPa |
| Tensile strength | 895–1,000 MPa | 1,241–1,380 MPa | 827–1,034 MPa |
| Strength-to-weight | Highest (~200) | High (~125–137) | Moderate (~49–78) |
| Elastic modulus | ~114 GPa | ~200 GPa | ~207 GPa |
| Thermal conductivity | 6.7 W/m·K | ~11.4 W/m·K | 9.8 W/m·K |
| Max service temp | ~350–400°C continuous | ~700°C | ~980°C short-term |
| Cutting speed (carbide) | 50–150 sfm | 60–150 sfm | 60–165 sfm |
| Machinability (vs 1212) | Difficult | ~12% | ~17% |
| Corrosion strength | Seawater, chlorides | Hot oxidation, acids | Pitting/crevice (PREN ~51) |
| Relative part cost | High | Highest | Highest |
| Typical uses | Airframe, implants, fasteners | Turbine disks, shafts, fasteners | Chemical, marine, exhaust |
Read the service-temperature row twice — it is the one line that actually separates these materials. Everything else is a matter of degree; that line is a cliff.
Temperature: The Line That Separates Them
At room temperature the two metals look evenly matched — both strong, both corrosion-resistant, both expensive. Turn up the heat and they diverge completely. Ti-6Al-4V is rated for continuous service only to about 350°C (roughly 660°F); above 400°C it loses strength, oxidizes, and creeps. Inconel was built precisely for that regime. Inconel 718 holds useful strength to ~700°C (1,300°F) — at 650°C it still carries roughly 925 MPa yield. Inconel 625 tolerates short-term exposure approaching 980°C (1,800°F).
That is why Inconel lives in turbine disks, exhaust components, combustion hardware, heat-treat fixtures, and downhole oil-and-gas tools, while titanium stays on the cooler side: airframe structure, fan blades, fasteners, and engine cases upstream of the hottest stages. If your part runs hot, this decision is already made for you.
Weight and Strength: Titanium’s Counterpunch
On weight, titanium is unbeatable here. Ti-6Al-4V at 4.43 g/cm³ is roughly 46–47% lighter than Inconel (8.19–8.44 g/cm³) — an Inconel part weighs about 85–90% more than the identical titanium geometry. On absolute strength, Inconel 718 counters: aged to 1,034–1,120 MPa yield and 1,241–1,380 MPa tensile, it is the strongest of the three, ahead of Ti-6Al-4V’s 880–930 MPa yield. But divide strength by density and titanium reclaims the crown — about 200 MPa of tensile strength per g/cm³ versus roughly 125–137 for Inconel 718 and well under 100 for Inconel 625.
So the honest summary: Inconel 718 is stronger in absolute terms; titanium is stronger per unit of weight. Inconel 625 is the softest of the three — its job is corrosion, not peak strength. For the wider titanium picture, see our titanium vs aluminum and titanium vs steel comparisons. Every yield and tensile number in this section comes off a stress-strain curve, which is also where the ductility difference between these alloys shows up.
Corrosion: Two Different Kinds of Immortality
Both metals resist corrosion superbly, but against different enemies. Titanium’s self-healing oxide film is legendary against seawater, chlorides, and body fluids — the reason it owns marine hardware, chemical processing, and implants. Inconel answers with a chromium-oxide film that shrugs off oxidation and most acids, and Inconel 625 adds outstanding pitting and crevice resistance (a PREN around 51) that makes it the default for sour-gas service, exhaust, and chemical plants. Inconel also keeps that protection at temperature, where titanium’s oxide film breaks down.
Choose titanium for room-temperature chloride and seawater duty; choose Inconel for hot, oxidizing, or acid environments. The stainless steels sit in the middle — genuinely excellent corrosion resistance at a fraction of either price — which our 304 vs 316 stainless comparison and passivation guide cover in detail.
Machinability: Both Fight You — Inconel Fights Harder
Both titanium and Inconel rank among the most difficult metals to machine, and for the same root cause: terrible thermal conductivity. Ti-6Al-4V conducts at 6.7 W/m·K, Inconel 625 at 9.8, and Inconel 718 at ~11.4 — a fraction of aluminum’s 167 or steel’s 42, so cutting heat piles up at the tool edge instead of leaving with the chip. What separates Inconel is work hardening. A single light or rubbing pass can harden Inconel 718 from ~36 HRC to 50–55 HRC in a 50–200 µm surface layer, so every following pass fights material harder than the last.
In practice both run at similarly slow carbide speeds — roughly 50–150 sfm for titanium, 60–165 sfm for Inconel — but Inconel demands larger, constant feeds (light cuts are actively counterproductive), positive-rake coated carbide, high-pressure coolant, and rigid setups, and its tool life is measured in minutes. Budget Inconel as the more expensive machining job of the two; between the Inconel grades, 625 is slightly more forgiving (machinability ~17% vs ~12% for 718 relative to 1212 steel). For features the mill cannot reach economically — deep slots, sharp internal corners, thin walls — wire EDM machining sidesteps the problem entirely, because there is no cutting force and no work hardening at the edge.
Cost: Nickel’s Premium, Paid Twice
Both materials are expensive before a single chip falls. Ti-6Al-4V stock typically runs $22–66/kg. Inconel 718 industrial bar can run $25–35/kg, but aerospace-certified, heat-treated, or specification-driven material climbs to $44–110/kg and beyond — nickel, niobium, and molybdenum are costly, and the melt and certification process adds more. Then machining multiplies it: as one of the two hardest metals to cut, Inconel racks up slow cycle times and heavy tool consumption, so fabrication, not raw stock, usually dominates the final part price for both alloys.
The practical rule: an Inconel part generally costs more than the same geometry in titanium, and both cost several times more than the same part in steel or aluminum. Specify either one because the environment demands it, never because it sounds premium.
Know the Grades, Then Decide
Ti-6Al-4V (Grade 5): 880–930 MPa yield, 4.43 g/cm³. The titanium workhorse — aerospace structure, fasteners, implants, and performance parts up to ~350°C.
Inconel 718: 1,034–1,120 MPa yield (aged), 8.19 g/cm³. Precipitation-hardened for high strength to ~700°C — turbine disks, shafts, fasteners, and cryogenic service.
Inconel 625: 414–655 MPa yield, 8.44 g/cm³. Solid-solution strengthened for corrosion and 980°C short-term heat — chemical, marine, exhaust, and sour-gas service.
Choose titanium for weight and room-temperature corrosion. Choose Inconel 718 for high strength at high temperature. Choose Inconel 625 for the nastiest corrosion and the hottest short-term exposure. Grade-by-grade details on our material pages: titanium CNC machining and stainless steel CNC machining. Related comparisons: titanium vs steel and steel vs aluminum.
Related: Ready to cut it? Our Inconel machining guide covers annealed vs aged condition, carbide speeds by operation, and the work-hardening rules.
Where Each Metal Actually Wins
Exhaust systems: the answer changes along the pipe. Near the engine — manifolds, headers, turbine housings, exhaust valves — the gas runs well past titanium’s comfort zone, and this is where Inconel earns its keep: 625 is the standard motorsport exhaust alloy, and 751 has been the racing exhaust-valve material for decades. Downstream, where the gas has already shed its heat — cat-back systems, mufflers, tips — titanium takes over: at 4.43 g/cm³ it builds the same layout at roughly half the weight, which is why aftermarket titanium systems are cat-backs, not manifolds. A titanium manifold is how you learn about creep.
Suppressors: the same trade, compressed. Titanium wins the scale — full erosion resistance up to about 750–800 °F (400–425 °C), fast cool-down between strings, at roughly half the weight of a same-size can in steel or nickel alloy. Past that temperature the muzzle blast starts eroding titanium baffles, and that is where Inconel takes the job: high-volume fire and short barrels that never get a cooling break. The design inside matters more than the alloy outside — but either alloy will make the machine shop work for its money.
Aerospace, cold end vs hot end: the engine splits itself at the temperature line. Titanium owns the cold end — fan blades, front compressor stages, airframe structure — everywhere strength-per-kilo decides and the metal stays under ~400 °C. Inconel 718 owns the hot end — turbine disks, shafts, casings around the combustor — where nothing titanium offers survives 700 °C. Neither metal is “better”; the engine is the demarcation.
Marine and chemical: both alloys shrug off seawater, so the decision moves to temperature and budget. Titanium is the lighter, cheaper answer for pumps, valves, and hull hardware at ambient temperature. When the chloride gets hot — heat exchangers, sour-gas service, crevice-prone flanges — Inconel 625 is the one that still has margin, with a PREN near 51 against a seawater threshold of 40. The same strength-to-weight logic at the other end of the price range: our titanium vs aluminum comparison runs that math.
FAQ
Which is stronger, Inconel or titanium?
On absolute strength, Inconel 718 wins: aged to a 1,034–1,120 MPa yield and 1,241–1,380 MPa tensile, it is stronger than Ti-6Al-4V’s 880–930 MPa yield. But “strong” depends on context. Divide strength by density and titanium reclaims the crown — about 200 MPa of tensile strength per g/cm³ versus roughly 125–137 for Inconel 718 — so titanium is stronger per unit of weight. Inconel 625 is the softest of the three at 414–655 MPa yield; its job is corrosion, not peak strength. For a fixed-weight part, titanium wins; for a fixed-size part at high temperature, Inconel 718 wins.
Is Inconel harder to machine than titanium?
Yes — marginally on speed, decisively on tool life. Both have terrible thermal conductivity (6.7 W/m·K for titanium, 9.8–11.4 for Inconel), so cutting heat concentrates at the tool edge, and both run at similarly slow carbide speeds (50–150 sfm for titanium, 60–165 sfm for Inconel). The difference is work hardening: a single light or rubbing pass can harden Inconel 718 from ~36 HRC to 50–55 HRC in the surface layer, so every following pass fights harder material. Inconel demands larger, constant feeds, positive-rake coated carbide, high-pressure coolant, and maximum rigidity, and its tool life is measured in minutes. Expect Inconel to be the more expensive machining job of the two.
Why is Inconel so expensive?
Nickel is the primary driver: Inconel is roughly 50–60% nickel, plus costly niobium, molybdenum, and chromium, and it needs demanding melting and certification processes. Industrial Inconel 718 bar runs about $25–35/kg, but aerospace-certified or specification-driven material climbs to $44–110/kg and beyond. Titanium is no bargain either (Ti-6Al-4V typically $22–66/kg), but aerospace-grade Inconel usually carries the higher raw price — and because it is one of the hardest metals to machine, fabrication, not stock, dominates the final part cost. Both materials cost several times more than the same part in steel or aluminum.
Inconel 625 vs 718 — what is the difference?
They get strong by different routes, which decides their roles. Inconel 718 is precipitation-hardened: heat treatment forms gamma-prime/gamma-double-prime precipitates that pin dislocations, giving it high strength (1,034–1,120 MPa yield) to about 700°C — the choice for turbine disks, shafts, and loaded fasteners. Inconel 625 is solid-solution strengthened by molybdenum and niobium: lower strength (414–655 MPa yield) but outstanding pitting and crevice resistance (PREN ~51) and tolerance of short-term heat to ~980°C — the choice for chemical processing, marine hardware, exhaust, and sour-gas service. For stress at high temperature, pick 718; for the nastiest corrosion, pick 625.
When should I use Inconel instead of titanium?
Choose Inconel when the part must hold strength above ~400°C, or resist hot oxidation: turbine and exhaust hardware, heat-treat fixtures, downhole oil-and-gas tools, and combustion components all belong to Inconel. Ti-6Al-4V softens, oxidizes, and creeps above 350–400°C, so it stays on the cooler side of the assembly — airframe structure, fan blades, fasteners, implants. Choose titanium when weight is the hard requirement (it is about 47% lighter than Inconel) or for room-temperature seawater and chloride duty. If neither heat nor weight dominates, a stainless steel often does the job for a fraction of the price.
Does Inconel rust?
No — Inconel is a nickel-chromium alloy and forms a protective chromium-oxide film that resists oxidation and most acids, and Inconel 625 adds outstanding resistance to pitting and crevice corrosion. Unlike carbon steel it needs no plating or coating, and unlike titanium it keeps that protection at high temperature, which is exactly why it survives in exhausts and combustion sections. The stainless steels occupy the middle ground — excellent corrosion resistance at a lower price than Inconel — which our 304 vs 316 comparison covers in detail.
Is Inconel stronger than titanium?
In absolute strength, yes: aged Inconel 718 yields at 1,034–1,120 MPa against 880–930 MPa for Ti-6Al-4V, and it keeps that strength to about 700 °C while titanium fades past 400 °C. Per unit of weight, no: titanium is almost half as dense, so its strength-to-weight ratio is the higher of the two — which is why airframes are titanium and turbine disks are Inconel. “Stronger” only means something once you say at what temperature and at what weight.
Inconel or titanium for exhaust headers?
Inconel, almost always. Header and manifold gas temperatures run well past titanium’s ~400 °C comfort zone, where titanium loses strength and creeps — that is why motorsport manifolds and racing exhaust valves are Inconel 625 and 751. Titanium enters downstream: cat-back systems and mufflers, where the gas has already cooled and its near-half-weight advantage comes free. If a quote covers a full titanium system including the manifold, ask what temperature margin the design has.
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Sources
Standards and references behind the numbers on this page.
- Special Metals, INCONEL alloy 718 datasheet (PDF) — manufacturer data: density, aged yield and tensile strength, service temperatures
- Special Metals, INCONEL alloy 625 datasheet (PDF) — manufacturer data for the 625 column
- MatWeb, Titanium Ti-6Al-4V (Grade 5) datasheet — the titanium side of the property table
- Silencer Shop, Titanium vs Stainless Steel Suppressors — the 750–800 °F titanium limit behind the suppressor section
Inconel and Titanium, Machined In-House
IsoCNC machines both families daily — from Ti-6Al-4V brackets to Inconel 718 and 625 aerospace and oil-and-gas components, with full material certs and inspection reports. Send the drawing; an engineer reviews every RFQ, typically within 1–2 business days.