Inconel 718 VS Inconel 625 Pipe:Which is Better?
Inconel 718 VS Inconel 625 Pipe:Which is Better?
Both Inconel 718 and 625 have their own advantages and disadvantages, and there is no absolute "better or worse" distinction. Inconel 625 is more suitable for highly corrosive environments (such as marine and chemical processing) and has better weldability. Inconel 718 is more suitable for applications requiring the highest mechanical strength and resistance to high-temperature stress.
What grade is Inconel 625 pipe?
Typically, this cold-worked Inconel 625 seamless pipe is supplied in two conditions: Grade 1 and Grade 2. ASTM B444 UNS N06625 Grade 1 pipe is supplied in the annealed condition, while Grade 2 pipe is supplied in the solution-annealed condition.
Inconel 718 Pipe vs Inconel 625 Pipe:Core Definitions
What is Inconel 718 pipe?
Inconel 718 tubing is a precipitation-hardening nickel-chromium superalloy. It contains significant amounts of niobium, molybdenum, and aluminum. These elements enable the metal to undergo age hardening.
This material exhibits extremely high yield strength and tensile strength, and maintains its structural integrity even at temperatures up to 700°C.
Inconel 718 Pipe Chemical Composition
| Ni + Co | Cr | Fe | Nb (Cb) + Ta | Mo |
| 50.0 – 55.0 | 17.0 – 21.0 | Balance | 4.75 – 5.50 | 2.80 – 3.30 |
| Ti | Al | Co | C | Mn |
| 0.65 – 1.15 | 0.20 – 0.80 | ≤ 1.00 | ≤ 0.08 | ≤ 0.35 |
| Si | Cu | P | S | B |
| ≤ 0.35 | ≤ 0.30 | ≤ 0.015 | ≤ 0.015 | ≤ 0.006 |
What is Inconel 625 pipe?
Inconel 625 tubing is a solid solution strengthened nickel-based alloy. Its strength primarily derives from molybdenum and niobium in the nickel-chromium matrix. Therefore, the required properties can be achieved without heat treatment.
This alloy exhibits excellent machinability and superior resistance to severe pitting corrosion.
Inconel 625 Pipe Chemical Composition
| Ni | Cr | Mo | Nb + Ta | Fe |
| ≥ 58.00 | 20.0 – 23.0 | 8.0 – 10.0 | 3.15 – 4.15 | ≤ 5.0 |
| Co | C | Mn | Si | Al |
| ≤ 1.00 | ≤ 0.10 | ≤ 0.50 | ≤ 0.50 | ≤ 0.40 |
| Ti | P | S | ||
| ≤ 0.40 | ≤ 0.015 | ≤ 0.015 |
3. Mechanical Strength Variance in Inconel 625 & inconel 718 Pipe
| Property | Inconel 718 Pipe | Inconel 625 Pipe |
| Strengthening Method | Precipitation Hardening | Solid Solution |
| Yield Strength | 1030 – 1180 MPa 150 – 171 ksi |
415 – 550 MPa 60 – 80 ksi |
| Tensile Strength | 1240 – 1400 MPa 180 – 203 ksi |
830 – 930 MPa 120 – 135 ksi |
| Elongation | 12 – 25% | 30 – 50% |
| Hardness | 36 – 44 HRC ~ 340 – 410 HB |
85 – 95 HRB ~ 160 – 200 HB |
| Density | 8.19 g/cm3 0.296 lb/in3 |
8.44 g/cm3 0.305 lb/in3 |
| Modulus of Elasticity | 200 GPa 29.0 Mpsi |
207 GPa 30.1 Mpsi |
| Thermal Conductivity | 11.4 W/(m · K) 79.1 Btu · in/hr · ft2 · ℉ |
9.8 W/(m · K) 68.0 Btu · in/hr · ft2 · ℉ |
| CTE | 13.0 μm/m · ℃ | 12.8 μm/m · ℃ |
| Specific Heat Capacity | 435 J/(kg · K) 0.104 Btu/lb · ℉ |
410 J/(kg · K) 0.098 Btu/lb · ℉ |
| Electrical Resistivity | 1.25 μΩ · m | 1.29 μΩ · m |
| Magnetic Properties | Non-magnetic at room temperature | Non-magnetic at room temperature |
| Melting Range | 1260 – 1336 ℃ 2300 – 2437℉ |
1290 – 1350 ℃ 2350 – 2460℉ |
4. Comparison of high-temperature performance between Inconel 718 and Inconel 625 tubing
| High-Temp Property | Inconel 718 Pipe | Inconel 625 Pipe |
| Max Service Temp | 650 – 700℃ 1200 – 1300℉ |
815 – 982℃ 1500 – 1800℉ |
| Strength Trend | Drops sharply above 650℃ | Decreases gradually;no sudden drop. |
| Yield Strength at 650℃ | ~ 850 – 950 MPa | ~ 300 – 400 MPa |
| Microstructural Stability | Poor abouve 700℃ | Excellent |
| Creep Resistance | Best at or below 650℃ | Superior at extended temps above 700℃ |
| Oxidation Resistance | Good,but limited at extreme temps due to high iron content. | Exceptional up to 980℃ due to high Cr and low Fe. |
5. Inconel 718 VS Inconel 625 Pipe:Corrosion Resistance
| Corrosion Parameter | Inconel 718 Pipe | Inconel 625 Pipe |
| PREN Value | ≈ 26 – 31 | ≈ 46 – 56 |
| Pitting & Crevice | Moderate-High | Excellent |
| SCC | Excellent | Outstanding |
| Sour Gas H2S & CO2 |
Excellent | Superior |
| Mineral Acids | Moderate | Excellent |
| Oxidizing Environments | Good | Excellent |
| Intergranular Corrosion | Susceptible | Highly Resistant |
6. International material standards and grades for Inconel 718 and Inconel 625 pipes
| Alloy | UNS | EN | DIN | W.Nr. |
| Inconel 718 | N07718 | NiCr19Fe19Nb5Mo3 | DIN 17751 | 2.4668 |
| Inconel 625 | N06625 | NiCr22Mo9Nb | DIN 17751 | 2.4856 |
7. Inconel 625 and Inconel 718 Tube Application Guide
Choose Inconel 718 Seamless Pipes if:
Your application involves rotating components, turbine discs, engine shafts, or high-pressure fuel manifolds. If your part must withstand massive centrifugal forces or high internal pressure without "stretching" (creeping) at temperatures up to 700°C, Inconel 718 is your only Cost-effective Solution.
Choose Inconel 625 Seamless Pipes if:
Your piping system handles aggressive chemical media like hydrochloric, sulfuric, or phosphoric acids, or operates in offshore splash zones. If preventing localized pitting and stress-corrosion cracking (SCC) is your #1 priority, Inconel 625 provides the Industrial Durability your system requires.
Why Choose Gnee as Your Nickel-Based Alloy Supplier
✅️VIM + VAR Melting: Double-vacuum refining ensures an ultra-clean microstructure, which is the key to maximizing the fatigue life of 718 and the corrosion integrity of 625.
✅️Total Traceability: Every pipe is heat-number stamped and accompanied by an EN 10204 3.1 MTC.
✅️Wholesale Pricing: Benefit from Direct Factory Price on bulk orders for aerospace and petrochemical maintenance (MRO) programs.
✅️Global Logistics: Fast shipping with specialized packaging to Europe, USA, and Southeast Asia.
Gnee Alloy Inconel 625 Certificate
📦 Packaging and Shipping
All Nickel Based Alloy products are packaged using the following methods:
Wooden pallets or crates
Moisture-proof packaging
Labels with furnace number, standard, and size labels
Shipped worldwide by sea, air, or express
Gnee Alloy Alloy 625 Product Packing
⚒️Gnee Alloy Production Line Equipment and Product Testing
Contact us for the latest export price quote for 625 Alloy
FAQ
Q1: Can I use Inconel 625 filler metal to weld Inconel 718 parts?
A: Yes, in many cases. ERNiCrMo-3 (Alloy 625 wire) is a common filler for 718 due to its high ductility. However, keep in mind that the weld joint will not have the same 700°C strength as the 718 base metal.
Q2: Does Inconel 718 meet NACE MR0175 for sour gas service?
A: Absolutely. Our Inconel 718 is specifically heat-treated to meet the hardness and microstructural requirements of NACE MR0175, making it the premier choice for high-pressure downhole tools.
Q3: Which alloy is more difficult to machine?
A: Inconel 718 is more challenging because it work-hardens even faster than 625. However, as a Specialized Manufacturer, we supply 718 bars and tubes in an optimized solution-treated state to maximize your CNC tool life.
Q4: Do you offer trial orders for small batch fabrication?
A: Yes. We support Innovation and R&D projects with Flexible MOQs on our standard wholesale stock.
