Grade dossier
403 Stainless Steel
403 stainless steel is a 12% chromium martensitic stainless grade identified as UNS S40300. ATI developed the controlled chemistry for turbine-blade construction, where corrosion and heat resistance must be combined with a high elastic limit, impact strength and properties that can be adjusted by hardening and tempering.
Identity before substitution
Specify 403 by product form, heat treatment and turbine-service requirement
403 is closely related to 410, but ATI specifies a tighter chromium range together with lower maximum silicon and nickel. The grade was developed for turbine-blade requirements rather than free machining. A controlled RFQ should therefore state the exact standard, flat-product form and thickness, annealed or hardened-and-tempered condition, target mechanical properties, heat-treatment route, surface condition and operating temperature/environment.
403 stainless composition
UNS S40300 chemistry reference
403 uses a tighter chemistry window than 410
ATI publishes S40300 with 11.50–13.00% chromium, 0.15% maximum carbon, 0.50% maximum silicon and 0.60% maximum nickel. ATI notes that the composition falls within its 410 limits but is intentionally tighter for turbine-blade construction. Use the controlling specification on the purchase order and verify the heat analysis on the MTC rather than treating an EN cross-reference as chemically identical.
| C | 0.15 max |
|---|---|
| Mn | 1.00 max |
| Si | 0.50 max |
| P | 0.040 max |
| S | 0.030 max |
| Cr | 11.50–13.00 |
| Ni | 0.60 max |
| Fe | Balance |
403 stainless properties
Use the delivered heat-treatment condition as part of the 403 specification
ATI 403 annealed — published minimum / maximum values
| Tensile strength | 483–485 MPa min |
|---|---|
| 0.2% yield strength | 205–207 MPa min |
| Elongation | 25% min* |
| Hardness | 96 HRB max |
ATI 403 hardened & tempered — published minimum / range values
| Tensile strength | 689 MPa min |
|---|---|
| 0.2% yield strength | 483 MPa min |
| Elongation | 18% min |
| Hardness | 93–100 HRB |
ATI states that 403 is available in annealed and hardened-and-tempered conditions and that other property levels can be produced by changing tempering parameters. *ATI notes 20% minimum elongation for material 0.500 in. and under in thickness. Treat these values as producer/specification guidance and verify the exact ordered condition and heat-specific MTC before acceptance.
Selection boundary
Use 403 when turbine-component strength, impact response and heat resistance drive the choice
ATI positions 403 around turbine-blade construction and notes that the grade combines atmospheric corrosion resistance, heat resistance, elastic limit and impact strength. It is not a severe-corrosion alloy, and its usable strength depends strongly on the selected hardening and tempering cycle.
Good reasons to evaluate 403
Steam-turbine and gas-turbine blades where controlled mechanical response is required.
Compressor blades and related rotating components after engineering review.
Components needing martensitic hardenability together with moderate atmospheric corrosion resistance.
Parts that will be supplied annealed and then hardened/tempered to a defined strength and toughness target.
Stop and review before release
Severely corrosive chemical or chloride-rich environments; ATI specifically states 403 is not recommended for severe corrosion.
Continuous high-temperature oxidation service above the producer guidance of roughly 649–704°C.
Tempering in the approximately 427–593°C range without engineering review, because impact properties and corrosion resistance can decrease.
Substitutions based only on the “12% chromium” family name without checking the tighter 403 chemistry and required condition.
Heat-treatment and fabrication route
Control annealing, hardening and tempering to obtain the required 403 properties
ATI publishes annealing at about 816–899°C, followed by a slow cool to about 593°C and then air cooling.
Full hardening can be obtained by oil quenching from about 899–982°C; light sections may use air or fan cooling, while thicker sections require faster cooling.
Tempering may be performed from about 204–760°C, but ATI advises avoiding roughly 427–593°C because impact properties and corrosion resistance can decrease.
For hot working, ATI recommends starting around 1093–1148°C and finishing above about 760°C. Final processing should be tied to the required blade or rotating-component property target.
403 stainless supplier checklist
Order 403 as a traceable martensitic flat product with the required heat-treatment condition
A 403 stainless supplier should identify the exact product form, thickness/width, tolerance, surface condition, heat-treatment condition and governing standard. ATI’s current product page identifies 403 plate and also routes inquiries for plate, sheet and strip. Public producer data does not establish this website’s live stock or a universal size range, so dimensional availability should be confirmed at quotation stage.
ATI product form reference: plate · sheet · strip inquiry channels
Published ASTM / AMS references: ASTM A176 · AMS QQ-S-763
UNS designation: S40300 · martensitic stainless steel
Closest EN cross-reference: 1.4000 / X6Cr13 — verify before substitution
MTC / test-report checkpoint
Verify heat number and traceability, UNS S40300, governing specification and edition, chemical analysis including the tighter Cr/Si/Ni limits, ordered form and dimensions, surface condition, annealed or hardened-and-tempered state, tensile/yield/elongation/hardness results required by the order and any supplementary inspection. A useful MTC excerpt should connect the heat identity, chemistry, mechanical result and delivered condition to the ordered lot.
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Interactive procurement check
Test 403 against the controlling design question
Procurement FAQ
Questions to close before ordering 403 stainless steel
What is 403 stainless steel?
403 is a 12% chromium martensitic stainless grade identified as UNS S40300. ATI developed its tighter chemistry for turbine-blade construction requiring corrosion and heat resistance together with a high elastic limit and impact strength.
What is the EN equivalent of 403 stainless steel?
1.4000 / X6Cr13 is commonly listed as the closest European cross-reference, but it is also associated with 410S-type material. Treat it as a cross-reference only, not an automatic one-to-one substitution; use the required UNS/standard and verify chemistry and mechanical requirements.
Can 403 stainless steel be hardened?
Yes. ATI publishes full hardening by oil quenching from about 899–982°C; light sections may also be air or fan cooled. The final strength, hardness, ductility and toughness depend on the subsequent tempering cycle.
What are the main service limits of 403 stainless steel?
ATI does not recommend 403 for severely corrosive environments. For oxidation service, ATI reports resistance up to about 760°C but recommends lower continuous-service temperatures of roughly 649–704°C depending on atmosphere and operating conditions.
What should a 403 RFQ include?
State UNS S40300, governing standard and edition, plate/sheet/strip form, dimensions and tolerances, surface condition, annealed or hardened-and-tempered condition, required tensile/yield/elongation/hardness values, heat-treatment route, operating temperature/environment, MTC requirement and any supplementary inspection.
Sources, scope and RFQ
Trace the 403 chemistry and heat treatment before approving turbine or rotating components
UNS S40300 identity, martensitic classification, 11.50–13.00% Cr chemistry, annealed minimum mechanical properties, density, ASTM A176 / AMS QQ-S-763 references and plate/product-contact evidence.
Turbine-blade design intent, comparison with 410 chemistry, annealed and hardened-and-tempered property requirements, corrosion/oxidation limits, hot working, annealing, hardening and tempering guidance.
1.4000 / X6Cr13 is commonly listed as a closest European cross-reference, but it should not be treated as chemically or mechanically identical to UNS S40300 without standard-by-standard review.
Use the current ASTM/AMS or project-specific material specification for the ordered form. The heat-specific MTC, agreed heat-treatment condition and application acceptance criteria—not a generic web table—control release.