1. Вступ
Nickel-based superalloys are the workhorses of modern high-temperature and corrosive-service engineering.
Two of the most widely used are Юнель 718 (США N07718) і Юнель 625 (США N06625).
Both are nickel-chromium alloys, but they were engineered for different primary performance goals: 718 for very high strength and creep/fatigue resistance in the 400–700 °C range, і 625 for exceptional corrosion/oxidation resistance and high-temperature stability.
This article compares them from metallurgy through application, supplying data and practical guidance so engineers can choose the right alloy for a given service envelope.
2. Why compare these two alloys?
На перший погляд, Юнель 718 і Юнель 625 are both “nickel superalloys,” but that similarity belies fundamentally different design philosophies and failure-mode envelopes.
Comparing them is not academic — it is a practical engineering step that directly determines safety margins, inspection intervals, manufacturing cost and whole-of-life economics.
Different design intents, different strengths
- Юнель 718 was deliberately engineered for mechanics: it is a precipitation-hardening alloy optimized to produce a very fine, coherent dispersion of γ″/γ′ precipitates after solution + старіння.
The result is exceptional tensile and yield strength, very good fatigue performance, and strong creep resistance in the roughly 400–700 ° C діапазон.
That combination is why 718 is ubiquitous in rotating machinery, high-load fasteners, turbine components and aerospace structural items where cyclic mechanical stresses and dwell loads dominate the failure spectrum. - Юнель 625 was engineered for environmental stability: високий У + Mo + NB levels produce marked solid-solution corrosion and oxidation resistance, together with microstructural stability at elevated temperatures.
625 is therefore the logical choice when the prime hazards are хімічна атака, pitting/crevice corrosion, chloride-induced SCC, or very aggressive oxidizing atmospheres, and where extensive welding or field repairs are expected.
3. Що таке Inconel 718?
Юнель 718 (Нас N07718) is a nickel-chromium-iron superalloy that was engineered as a високоміцна, високотемпература structural material.
Its defining attribute is that it is precipitation-hardenable: after solution treatment and a controlled aging cycle it precipitates fine,
coherent Ni₃Nb (C ″) and Ni₃(Al,На) (C ′) particles that produce very high yield and tensile strength while retaining useful ductility and fracture toughness.
Because of that combination — plus good oxidation resistance — 718 is a standard choice for highly stressed parts in aerospace, Генерація живлення, нафта & gas and space applications.
Основні особливості
- Precipitation hardening for exceptional strength.
When properly heat treated, 718 develops a dense dispersion of γ″/γ′ precipitates.
Typical peak-aged tensile strengths are in the ~1.2–1.4 GPa range and 0.2% yield strengths around ~1.0–1.1 GPa (values depend on product form and temper).
Це робить 718 one of the strongest age-hardening Ni-based alloys usable at elevated temperatures. - Good creep and fatigue resistance at intermediate high temperatures.
Its designed service window is roughly 200–700 ° C; 718 retains superior creep/rupture life and fatigue endurance in that band compared with solid-solution alloys. - Balanced toughness and ductility for structural use.
Despite high strength, peak-treated 718 maintains workable elongation (зазвичай >10% depending on condition) and fracture toughness adequate for rotating and load-bearing parts. - Acceptable corrosion and oxidation resistance.
Its Cr/Ni balance gives reasonable resistance to oxidation and many industrial atmospheres, хоч pitting and chloride-induced SCC resistance is inferior to high-Mo alloys (Напр., Юнель 625). - Form factors & supply forms.
Widely available as forgings, бар, тарілка, аркуш, tubing and investment castings. Aerospace applications often use forged or wrought forms with tight metallurgical control. - Fabrication considerations.
718 is weldable, but welding alters the age-hardening microstructure; post-weld solution and aging treatments are typically required for critical, Високосильні компоненти.
У віці 718 is relatively hard to machine; manufacturers often supply it solution-treated for fabrication and then age after final machining. - Типові програми (ілюстративний): turbine discs and shafts, high-strength fasteners and bolts, rocket motor structures, hot-section components requiring both strength and toughness.
4. Що таке Inconel 625?
Юнель 625 (Нас N06625) є високонікелевим, high-molybdenum, niobium-stabilized alloy formulated for exceptional corrosion resistance and thermal stability.
На відміну від 718, 625 obtains its performance primarily through зміцнення твердого розчину (high Ni content with Mo/Nb additions) rather than by a precipitation-hardening route.
The alloy is renowned for resisting pitting, crevice corrosion and chloride stress-corrosion cracking; it is also easy to weld and fabricate, which has made it a workhorse in chemical processing, subsea and nuclear environments.
Основні особливості
- Видатна резистентність до корозії.
Високий Ni + Mo + Nb chemistry gives excellent resistance to піттінг, crevice corrosion and chloride SCC, and strong performance in many reducing and oxidizing acids and seawater environments.
Це робить 625 a default choice where corrosion drives failure risk. - Solid-solution stability & high-temperature oxidation resistance.
The stable austenitic matrix resists phase changes and embrittling intermetallics over a wide temperature range.
625 is frequently specified where chemical stability or oxidation resistance at elevated temperatures потрібно (service up to ~900 °C in some oxidation environments,
although long-term load-bearing (повзати) capability is lower than 718 in the 400–700 °C band). - Excellent weldability and repairability.
625 is forgiving to fusion welding and typically does not require post-weld aging to recover properties, simplifying fabrication and field repairs.
It is commonly used as weld filler or for cladding/overlay applications when corrosion resistance is required on a structurally different substrate. - Good ductility and toughness.
In the annealed condition 625 typically displays elongations ~30% and moderate hardness (≤~240 HB), facilitating forming and machining compared with hardened 718. - Form factors & supply forms.
Readily available in plate, труба, бар, трубка, weld consumables and cast forms; used widely for cladding and corrosion-resistant linings. - Типові програми (ілюстративний): subsea valves and fittings, chemical-process heat exchangers and piping, ядерні компоненти, exhaust components and cladding for corrosion-sensitive parts.
5. Хімія & metallurgy — what makes each alloy tick
This section gives the practical, engineering-level chemistry for Юнель 718 і Юнель 625, and explains how specific elements and their interactions create the alloys’ characteristic microstructures and properties.
Numbers are typical compositional ranges by weight percent used by designers and procurement engineers; always confirm with the supplier’s certified chemical analysis for the batch you buy.
Юнель 718 (США N07718) — typical specification window
| Елемент | Типовий діапазон (мас.%) | Нотатки |
| У | 50.0 - 55.0 | Principal matrix element (austenitic matrix). |
| Cr | 17.0 - 21.0 | Окислення та корозійна стійкість; stabilizes matrix. |
| Феод | bal. (≈ 17 - 21 типовий) | Balance element; змінний. |
| NB + Зіткнення | 4.75 - 5.50 | Primary strengthening element (γ″ formation). |
Mo |
2.80 - 3.30 | Solid-solution strengthener; contributes to corrosion resistance. |
| На | 0.65 - 1.15 | Contributes to γ′ and carbide chemistry; works with Al. |
| Al | 0.20 - 0.80 | γ′ former; helps high-temperature strength. |
| C | ~0.03 – 0.08 | Carbide former — controlled to limit grain-boundary carbides. |
Мн |
≤ 0.35 | Impurity/ minor alloying. |
| І | ≤ 0.35 | Impurity/ deoxidizer residual. |
| S, С | відстежувати (дуже низький) | Kept minimal to avoid embrittlement. |
| Б, ZR (сліди) | very small ppm levels | Controlled trace additions (B ~0.003–0.01%) may be present to improve creep/ grain-boundary properties. |
Юнель 625 (США N06625) — typical specification window
| Елемент | Типовий діапазон (мас.%) | Нотатки |
| У | ≥ 58.0 (балансувати) | Dominant matrix element (high-Ni austenite). |
| Cr | 20.0 - 23.0 | Corrosion/oxidation resistance. |
| Mo | 8.0 - 10.0 | Major contributor to pitting/crevice resistance and solid-solution strengthening. |
| NB + Зіткнення | 3.15 - 4.15 | Nb stabilizes carbides and improves strength/corrosion resistance. |
Феод |
≈ ≤ 5.0 | Minor balance element. |
| C | ≤ 0.10 | Kept low; carbides controlled. |
| Мн, І | ≤ 0.5 кожен | Minor constituents (deoxidation and process residuals). |
| П. | typically very low (керований) | Nitrogen may be controlled to improve strength/pitting resistance in some sub-grades. |
| S, С | відстежувати (дуже низький) | Minimized to avoid embrittlement/segregation. |
6. Мікроструктура & strengthening mechanisms
- 718: Age-hardening alloy. The principal hardening phase is the metastable Ni₃Nb (C ″), with a contribution from Ni₃(Al,На) (C ′).
Proper solution treatment + aging produces a fine, dense precipitate distribution that pins dislocations and yields high yield/tensile strength and creep resistance.
Control of δ-phase (orthorhombic Ni₃Nb) and carbides matters because coarse δ or carbides reduce toughness and ductility. - 625: Solid-solution strengthened with some short-range ordering from Nb and Mo; це робить не rely on a precipitation-hardening cycle.
The microstructure is a stable austenitic (Кубічний) matrix with high Ni content that resists phase transformations and maintains toughness and ductility even after welding or at elevated temperatures.
This stability also helps avoid embrittling phases in many environments.
7. Механічні властивості: Юнель 718 vs Inconel 625
(Представник, nominal values — always confirm with mill/ supplier certificates for your exact product form and temper.)
| Власність | Юнель 718 (solution treated & у віці) | Юнель 625 (відпалений / типовий) |
| Нас | N07718 | N06625 |
| Щільність (G · CM⁻³) | ~8.19. | ~8.44. |
| Сила на розрив (Rm) | ≥ ~1,200–1,380 MPa typical (у віці). | ~690–930 MPa (відпалений, залежить від продукту). |
| Похідна сила (0.2% компенсація) | ≥ ~1,030 MPa (у віці) типовий. | ~275–520 MPa (відпалений, ranges depend on product/form). |
Подовження |
≥ ~12% (у віці; condition dependent). | ~ 30% (annealed typical). |
| Твердість | ≈ 330–380 HB (теплообробка). | ≈ ≤240 HB (відпалений). |
| Typical high-use temperature (структурний) | Excellent up to ~650–700 °C for load-bearing service. | Used in hotter/oxidizing services up to ~900 °C for oxidation/corrosion resistance, but creep strength lower than 718 at moderate temps. |
Інтерпретація:
718 is markedly stronger in the heat-treated condition (higher yield and tensile strength), де 625 offers better ductility and corrosion performance with reasonable strength in the annealed state.
8. High-Temperature Performance Comparison
High-temperature performance is a compound measure: Окислювальна стійкість, Фазова стабільність, short- and long-term strength (creep and rupture), термічна втома, and dimensional stability under thermal cycling all matter.
| Аспект | Юнель 718 | Юнель 625 |
| Design/structural temperature window | Best structural use ≈ 200–650/700 °C (precipitation-hardened strength and creep resistance). | Solid-solution stability up to більш високі температури (~800–980 °C) for corrosion/oxidation service, але lower creep strength ніж 718 in the 400–700 °C range. |
| Creep/rupture strength | Вищий in 400–700 °C range because of γ″/γ′ precipitates; proven long-term creep resistance when correctly heat treated. | Помірний; good for some high-T applications but inferior creep strength under high stress vs 718. |
| Термічна стабільність / Фазова стабільність | Requires controlled heat treatment; excessive exposure near δ-formation ranges (~650–980 °C) can precipitate δ/Laves phases that degrade toughness. | Microstructure is more thermally stable (no γ″ precipitation to dissolve); less sensitive to typical welding/thermal cycles. |
Окислювальна стійкість |
Добрий (chromia-forming), but limited at extreme oxidizing conditions vs some higher-Ni/Mo alloys. | Відмінний, especially in oxidizing or sulfidizing atmospheres because of high Ni+Mo and stable scale formation. |
| Thermal fatigue (cycling) | Good when design keeps temperature within precipitate-stable range; fatigue resistance benefits from high strength. | Good resistance to thermal cycling from oxidation/scale spallation perspective; lower stress fatigue performance under high mechanical load. |
| Typical engineering consequence | Use where mechanical life (повзати, втома, rupture) controls design. | Use where environmental stability (corrosion/oxidation at elevated T) and weldability control design. |
9. Heat-Treatment Comparison
Heat treatment is the single most important processing step for 718 and a relatively simple step for 625.
The chosen cycles define microstructure, механічна поведінка, і довгострокову стабільність.
Юнель 718 (опадів)
- Лікування розчином: dissolve undesirable Laves/δ and solute atoms — typical range 980–1,020 °C (some specs use 1,030 ° C), hold to equalize chemistry, then water-quench.
This produces a homogeneous γ matrix with solute in solid solution. - Старіння (two-step, common commercial practice): first aging at ~720–740 °C на кілька годин, controlled cooling to ~620–650 °C with a further hold, then air cool to ambient.
This sequence produces the C ″ (N₃nb) dominant precipitates and some γ′.
Many OEMs use a standard “718 aging” such as 720 ° C × 8 h → cool to 620 ° C × 8 h → air cool (times/temps vary by spec and section thickness). - Sensitivities: incorrect solutionizing, insufficient quench rate, над- or under-aging produce coarse precipitates, δ phase or Laves that reduce toughness and fatigue life.
Післяопрез (Pwht) is frequently required for critical assemblies to re-establish peak properties.
Юнель 625 (Рішення відпалити / відпалений)
- Відпалити / Лікування розчином: common to anneal or solution treat 625 в ≈980–1,150 °C to dissolve any precipitates or homogenize segregation, Потім повітря круто; the alloy generally does not require aging to gain strength.
- Sensitivities: 625 is tolerant of welding and thermal excursions; avoid prolonged exposure in ranges that might promote deleterious intermetallics if unusual alloy additions are present.
For improved creep or specific microstructures, specialized sub-grades or processing may be specified.
10. Корозія, Окислення, and Environmental Resistance
- Юнель 625: outstanding resistance to піттінг, crevice corrosion and chloride-induced stress-corrosion cracking thanks to high Ni + Mo and Nb levels.
It resists a wide range of reducing and oxidizing acids, seawater and many aggressive media — that is why it’s common in chemical processing, subsea and nuclear applications. - Юнель 718: good general corrosion and oxidation resistance (good Cr/Ni levels) але not as intrinsically resistant to pitting or chloride SCC as 625. 718 is often used where corrosion exposure is moderate but where mechanical performance dominates.
Якщо 718 must be used in severe corrosive settings, protective measures (покриття, design details) or alloy alternatives (625, 625 обшивка, or higher-Mo alloys) are considered.
11. Виготовлення, Зварювання, and Manufacturability
Fabrication behavior drives manufacturability, repairability, і вартість. Below are practical, high-value notes.
Зварювання & приєднання
Юнель 625
- Відмінна зварюваність. Tolerant of common fusion welding processes (Gtaw / turn, Gmaw/mig, Махати).
- Метал наповнювача: commonly welded with matching Ni-Cr-Mo fillers (Напр., commercial ERNiCrMo-type consumables) to retain corrosion resistance.
- No mandatory aging: welds generally do не require post-weld aging for corrosion or toughness recovery; toughness and ductility remain high.
- Common use as filler/clad: because of this weld tolerance, 625 is used widely as weld overlay/cladding to protect substrates.
Юнель 718
- Weldable but sensitive. Welding disturbs the precipitate distribution; післяопрез (Pwht) or at minimum an appropriate aging cycle is often required for critical parts to recover mechanical properties.
- Метал наповнювача: use matching Ni-Cr-Fe-Nb fillers formulated for 718 to minimize dilution effects.
- HAZ control: the heat-affected zone can form δ/Laves or coarsen precipitates—control interpass temps and use qualified WPS/PQR.
- Repair complexity: field repairs are possible but must be planned with PWHT capability if recovery of strength is required.
Machinability and forming
- Обробка: both are more difficult to machine than carbon steels; 718 in the aged/hardened condition is markedly harder.
Typical practice is to машина 718 in solution-treated (м'який) хвороба, then perform final aging. 625 (відпалений) machines and forms more readily.
Use high-performance tooling, Низькі швидкості різання, and flood cooling to minimize work hardening and tool wear. - Формування: 625 offers excellent ductility for forming operations; 718 must be formed in soft condition before aging. Холодна робота 718 after aging can cause cracking.
Виробництво добавок (Амор) & Порошкова металургія
- AM suitability: both alloys are widely used in laser-powder bed fusion (LPBF) and directed-energy deposition (Сідати) процеси.
-
- 718: widely used in AM for aerospace; requires careful control of thermal history and post-build solution + старіння and often HIP to remove porosity and develop full strength.
- 625: popular in AM for complex corrosion-resistant components; Амор 625 often requires HIP/solutionizing for best ductility and defect closure but no precipitation aging.
- AM risks: пористість, anisotropy and residual stress—specify HIP, heat treatment and NDT for critical parts.
12. Вартість, availability and standards
- Вартість матеріалу: varies with nickel and molybdenum market prices. In some markets Inconel 625 (higher Ni & Mo) can be more expensive per kg than 718,
but total life-cycle cost (including maintenance and replacement) often favors 625 when corrosive environments would shorten component life.
Check current commodity pricing and supplier lead times. - Наявність & specs: both alloys are standardized and widely available in bars, поробка, тарілка, tube and weld filler forms.
Typical references: США N07718 (718) and UNS N06625 (625) and ASTM/ASME product specifications — verify the specific product standard required for procurement.
13. Заявки Inconel 718 vs Inconel 625
Обидва Юнель 718 і Юнель 625 are widely used across high-performance engineering industries.
Аерокосмічна та авіація
- Gas turbine discs and compressor rotors (Юнель 718)
- Turbine shafts, high-strength fasteners, і болти (Юнель 718)
- Aircraft engine exhaust systems and thrust reverser components (Юнель 625)
- Combustor liners and ducting exposed to oxidation and thermal cycling (Юнель 625)
Нафта & Gas and Subsea Engineering
- High-pressure wellhead components and downhole tools (Юнель 718)
- Subsea fasteners and structural connectors subjected to high loads (Юнель 718)
- Subsea pipelines, flexible risers, and cladding for offshore equipment (Юнель 625)
- Seawater injection systems, підводні клапани, and manifolds (Юнель 625)
Генерація живлення (Gas Turbine and Nuclear)
- Gas turbine rotor components and high-temperature bolts (Юнель 718)
- Steam turbine fasteners and structural supports (Юнель 718)
- Heat-exchanger tubing, сиволо, і компенсаційні шви (Юнель 625)
- Nuclear reactor coolant system piping and structural components (Юнель 625)
Chemical Processing and Petrochemical Industry
- Reactor internals and high-strength fasteners exposed to thermal cycling (Юнель 718)
- Pressure vessel components requiring structural reliability (Юнель 718)
- Acid-handling equipment, насос, і клапани (Юнель 625)
- Heat-exchanger tubing and chemical process piping (Юнель 625)
Marine and Offshore Infrastructure
- High-strength marine fasteners and connectors (Юнель 718)
- Subsea structural hardware exposed to cyclic loads (Юнель 718)
- Seawater-exposed components such as pump shafts and propeller elements (Юнель 625)
- Offshore platform piping systems and corrosion-resistant cladding (Юнель 625)
Automotive and High-Performance Motorsports
- Turbocharger turbine wheels and high-strength exhaust fasteners (Юнель 718)
- Racing engine valve components and structural exhaust hardware (Юнель 718)
- Exhaust systems and thermal shielding components (Юнель 625)
- High-temperature piping and manifolds (Юнель 625)
Additive Manufacturing and Advanced Engineering
- Complex aerospace structural parts produced by additive manufacturing (Юнель 718)
- High-strength lattice structures and turbine components (Юнель 718)
- Corrosion-resistant AM components for chemical processing equipment (Юнель 625)
- Custom heat-exchanger and flow-path components (Юнель 625)
14. Юнель 718 vs Inconel 625 — Key Differences
Нотатки: values are representative engineering ranges from typical supplier datasheets and engineering references.
Always confirm exact composition, mechanical data and heat-treatment schedules from the supplier’s MTR and applicable specifications before final design or procurement.
| Topic | Юнель 718 | Юнель 625 |
| Primary design intent | Високий Структурна міцність, повзати & fatigue resistance in the ~200–700 °C band (precipitation-hardening alloy). | Корозія / Окислювальна стійкість and high-temperature environmental stability; зміцнено тверде рішення. |
| Нас | США N07718 | США N06625 |
| Strengthening mechanism | Затвердіння опадів | Зміцнення твердого розвороту |
| Типова міцність на розрив (Rm) | ~1,200–1,380 MPa (peak aged; залежить від продукту). | ~690–930 MPa (відпалений; залежить від продукту). |
| Типовий межа текучості (0.2% компенсація) | ~1,000–1,100 MPa (у віці). | ~275–520 MPa (відпалений; wide range by product). |
| Твердість (typical HB) | ~330–380 HB (aged/hardened). | ≤ ~240 HB (відпалений). |
Щільність |
~8.19 G · CM⁻³ | ~8.40–8.44 g·cm⁻³ |
| Useful structural temperature | Best structural/cyclic service up to ~650–700 °C. | Good environmental stability/oxidation resistance to більш високі температури (~800–980 °C), but lower creep strength under high stress. |
| Повзати / rupture performance | Вищий in 400–700 °C range (designed for creep resistance). | Помірний; performs well for corrosion/oxidation stability but inferior creep strength vs 718 at moderate T. |
| Піттінг / щілина / хлоридна стійкість | Good general corrosion resistance but less resistant to pitting/SCC vs high-Mo alloys. | Відмінний pitting/crevice and chloride SCC resistance (high Mo + У + NB). |
Окислювальна стійкість |
Добрий (chromia forming), but less robust in the harshest oxidizing/sulfidizing atmospheres vs 625. | Excellent oxidation and sulfidation resistance in many aggressive atmospheres. |
| Зварюваність / ремонт | Weldable but sensitive — welding disturbs precipitates; PWHT and controlled aging often required for critical parts. | Відмінна зварюваність; retains toughness and corrosion resistance after welding; often used as filler/clad. |
| Виготовлення / обробка | Difficult in aged condition; типово machined in solution-treated (м'який) хвороба then aged. | More ductile and easier to form/machine in annealed condition; favorable for field repairs. |
Heat-treatment requirements |
Critical: Лікування розчином + controlled aging (two-step aging) to develop γ″/γ′. | Typically used annealed/solutionized; no precipitation aging required for service properties. |
| Typical industries / компоненти | Aerospace rotating parts, Турбінові диски, high-strength fasteners, rocket components, high-load shafts. | Chemical process equipment, subsea valves/manifolds, heat-exchanger tubing, cladding/overlay, ядерні компоненти. |
| Переваги | Very high yield/tensile strength; excellent fatigue and creep life in intended T range. | Outstanding corrosion/pitting resistance; easy welding/repair; thermal/oxidation stability. |
Обмеження |
Less resistant to aggressive chloride environments; fabrication requires precise heat treatment; higher machining difficulty in aged state. | Lower peak structural strength and creep life at moderate temperatures vs 718; somewhat higher raw-material cost due to Ni/Mo content. |
| Коли вибрати | Коли mechanical life (повзати, втома, stress-rupture) is the controlling failure mode. | Коли environmental attack (pitting/crevice/SCC, окислення) or fabrication/weldability is controlling. |
| Hybrid strategy | Often paired with 625 cladding/inserts where corrosion exposure exists but 718 is required structurally. | Often used as cladding or filler over structural substrates (включаючи 718 ядра) для захисту від корозії. |
15. Висновки
Коротка відповідь: There is no single “better” alloy — Юнель 718 і Inconel 625 excel at different problems.
Вибирати 718 when mechanical life (міцність, fatigue and creep) is the dominant design driver; вибирати 625 when environmental resistance (pitting/crevice/SCC, окислення) and fabrication/weldability are dominant.
Where both demands exist, use a hybrid solution (Напр., 718 structural core + 625 cladding/inserts) or evaluate alternate alloys engineered for the combined requirement.
Поширені запитання
Which alloy is better for turbine discs and highly stressed fasteners?
Юнель 718. Its precipitation-hardening (γ″/γ′) microstructure delivers far superior yield, tensile and creep/fatigue performance in the ~200–700 °C band.
Which alloy should I choose for subsea valves and seawater service?
Юнель 625. Високий Ni + Mo + Nb chemistry provides excellent resistance to pitting, crevice corrosion and chloride SCC in seawater environments.
Can I weld Inconel 718 without post-weld heat treatment?
You банкнота weld it, but for high-strength applications welding disturbs the precipitation state.
For critical components, controlled PWHT (розчин + старіння) is often required to restore specified properties.
Which alloy resists stress-corrosion cracking better?
625 generally exhibits better resistance to chloride-induced SCC than 718.
Однак, SCC resistance depends on temperature, стрес, surface condition and environment—testing is recommended for critical services.
Is a hybrid approach (718 ядро + 625 одягнений) практичний?
Yes — a common engineering solution: використання 718 for load-bearing structure and 625 overlay/cladding or inserts to protect exposed surfaces from corrosive attack.
Ensure metallurgical compatibility and qualified welding/cladding procedures.
Which alloy is better for additive manufacturing (Амор)?
Both are used in AM. 718 is common for high-strength aerospace AM parts but requires careful post-build solution + старіння (and often HIP).
625 is popular for corrosion-resistant AM parts and usually needs HIP/solutionizing for full density but no aging.
