The short answer
**IN625** and **IN718** are both nickel superalloys buyers meet in CNC and metal AM RFQs, but they are not interchangeable on drawings or in **rates.v1.1** estimate bands. IN718 is precipitation-hardenable and common for high-strength brackets and housings; IN625 is solid-solution strengthened and often chosen for corrosion / weldability / fabricability stories. Process choice (CNC from bar vs SLM + machined datums) still depends more on geometry than on the alloy name alone.
Illustrations use an **Example part** only—no customer cases.
Quick property framing for buyers (not a datasheet)
Treat this as RFQ orientation, then confirm with your material cert requirements:
- **IN718:** age-hardenable; strength after heat treat is a frequent design reason; machining in aged condition is harder on tools than annealed stock sequences
- **IN625:** excellent corrosion resistance narrative; typically not used where IN718’s aged strength is the point
- Both: low thermal conductivity, work hardening, tool wear—CNC time coefficients in planning rates are elevated versus aluminum
Do not paste marketing tensile numbers into a prototype RFQ unless your drawing requires them.
rates.v1.1 estimate context (planning only)
Public planning inputs authorized for display (estimates, ranges—not firm quotes):
- Bar $/kg order-of-magnitude: IN718 ~55, IN625 ~60
- SLM powder $/kg: IN718 ~120, IN625 ~130
- CNC machine-time coefficients: IN718 and IN625 both ×2.5 versus baseline aluminum-class time
- Line value above configured USD thresholds for hot alloys → **needs_manual** (auto min/mid/max stops; engineer continues)
Always confirm the live band on [quote-new.php](https://3dwk.com/quote-new.php). Related: [SLM vs CNC for IN718 brackets](https://3dwk.com/resources/slm-vs-cnc-inconel-718-brackets-cost-lead-time), [CNC cost drivers](https://3dwk.com/resources/cnc-machining-cost-drivers-buyer-guide), [reading preliminary quotes](https://3dwk.com/resources/reading-preliminary-online-quote-min-mid-max).
When CNC from bar is the default
Prismatic lugs, orthogonal hole patterns, modest buy-to-fly, wrought grain direction called on the drawing—CNC bar usually wins. Stock forms and heat-treat sequence must appear on the PDF (annealed machine → age, or machine after age for critical fits). Leaving “Inconel” without grade and condition is a classic needs_manual trigger.
When SLM + CNC datums competes
Lattice, internal channels, organic lightening, or envelopes that would scrap most of a billet push toward SLM powder with machined seals/dowels. Powder rates are higher per kg than bar, but buy-to-fly can flip the economics. Parallel RFQs (CNC and SLM+CNC) are legitimate for **Example part** trade studies.
Illustration 1 forks an **Example part** bracket: prismatic path → CNC bar; lattice path → SLM + datum machining.
IN625 vs IN718 on the RFQ line
Write the grade, product form, and heat-treat / condition explicitly:
- “IN718 bar, machine annealed, age to XXX, finish bore after age”
- “IN625 bar, as-machined, no age cycle”
- “IN718 SLM, HIP/heat-treat program per note, machine datums A/B”
If corrosion media drives IN625 but the geometry is a thick prismatic pad, say why you are not using a cheaper stainless—procurement will ask.
Tooling, lead time and inspection expectations
Nickel alloys consume inserts and cycle time. Lead-time guides still apply: stock availability, heat-treat queue, and CMM on tight bores dominate more than “upload second.” See [CNC lead time](https://3dwk.com/resources/cnc-machining-lead-time-buyer-guide). FAI expectations belong on regulated programs—do not assume every prototype line includes full FAI unless requested ([FAI reports](https://3dwk.com/resources/first-article-inspection-reports)).
Quote engine behavior buyers should expect
Automatic bands use material $/kg, time coefficients, finishes, qty breaks, and uncertainty display around mid (**rates.v1.1** public range concept). High line totals, huge bounding boxes, or incomplete condition notes → **needs_manual**. That flag is continuation, not rejection.
Illustration 2 maps grade + process + completeness to auto band vs needs_manual for an **Example part** RFQ.
Substitution pitfalls
Substituting IN625 for IN718 (or the reverse) without engineering approval is not a purchasing shortcut. Strength, fatigue, and corrosion assumptions differ. On prototypes labeled **Example part** trade study, state that the alloy is a stand-in if that is true—so finishes and certs are not over-applied.
What to upload
STEP + PDF, grade, condition, qty, finish, and whether CNC or SLM is intended. Service links: [CNC](https://3dwk.com/cnc-machining-service.php), [3D printing](https://3dwk.com/3d-printing-service.php), [materials](https://3dwk.com/materials.php). Start on [quote-new.php](https://3dwk.com/quote-new.php).
Common questions
Is IN625 always more expensive than IN718 in the online band?
Bar and powder planning rates for IN625 are slightly higher in **rates.v1.1** estimate cards, but geometry, heat treat, and qty dominate. Compare live bands; do not hard-code blog numbers into POs.
Can I leave heat treat as “vendor recommend”?
You can, but expect needs_manual or clarifying questions on strength-critical IN718. Prefer a named sequence when fits are finished after age.
Does SLM powder price mean SLM always costs more?
No. Buy-to-fly and machining hours can outweigh powder $/kg. Run both paths when geometry is ambiguous.
Stock forms and documentation notes
Call plate vs round bar when the envelope makes buy-to-fly obvious. If your drawing inherits aerospace notes (AMS specs, grain direction, freeze processes), say which notes apply to this prototype lot versus which are production-only. Prototype RFQs that paste full production quality codes without marking them optional often stall in manual review—even when the solid model is simple.
Corrosion vs strength decision sketch
If the failure mode of interest is aqueous corrosion or chemical exposure, IN625 frequently appears in engineering discussions. If the failure mode is high tensile / fatigue after heat treat in a structural bracket, IN718 is the more common grade conversation. Neither sentence replaces your materials engineer—label trade-study uploads as **Example part** intent when you are still deciding.
Mixed carts and dual processes
A cart that mixes IN718 CNC clips with IN625 SLM manifolds may auto-price one line and flag the other. Read per-line status. Approving only the automatic line while ignoring manual flags creates partial orders shops cannot schedule cleanly—same discipline as other multi-process carts on [quote-new.php](https://3dwk.com/quote-new.php).