Inconel 690 and Inconel 600 tubes have different amounts of chromium in them and different performance possibilities. While Inconel 600 only has 14-17% chromium, Inconel 690 tube has 28-31%. This makes Inconel 690 better at resisting both rust and oxidation when exposed to high temperatures. While both alloys are useful in tough situations, Inconel 690 shows much better resistance to stress corrosion cracking in steam generators. This makes it the better choice for nuclear power uses and harsh chemical processing conditions.
Chemical Composition Analysis: The Foundation of Performance Differences
Looking at the chemicals that make up these alloys explains why they work better or worse in different situations. The elements added to the metals affect how well each one resists rust and breaking down at high temperatures.
The chemicals that make up Inconel 690:
- Nickel (Ni): at least 58%
- Chromium (Cr): 28% to 31%
- Fe: 9-11%
- Carbon (C): No more than 0.05%
- Manganese (Mn): no more than 0.5%
Inconel 600: What Chemicals Is It Made Of?
- Nickel (Ni): at least 72%
- Chromium (Cr): 14% to 17%
- Fe: 6-10%
- C: at most 0.15%
- Manganese (Mn): no more than 1.0%
Inconel 690 has more chromium in it, which makes a safer layer of oxide. This better passivation layer stops intergranular attack much better. The lower carbon level also lowers the chances of carbide precipitation during soldering.
If you need to prevent maximum corrosion in environments that oxidize, Inconel 690 is a better choice. Inconel 600 might be better for your use if you need more nickel in order to get certain metallurgical qualities.
Corrosion Resistance Performance: Critical Differences in Harsh Environments
The most important way that these alloys are different from each other is how well they prevent corrosion. Lab tests show that they behave very differently in different acidic media.
Inconel 690 has three important corrosion protection benefits:
- Better protection against stress corrosion cracking in areas with pressurized water reactors
- Better resistance to intergranular rust in acidic liquids
- Better protection against oxidation at temperatures over 1000°C
Inconel 690 is eaten away less than 0.1 mm/year in boiling 65% nitric acid, according to ASTM G28 Method A test results. Inconel 600 comparable tests under the same conditions shows corrosion rates close to 0.5 mm/year.
The Inconel 690 tube is great at resisting rust in the secondary water chemistry of steam generators. When the right kind of heat treatment is used, almost no stress corrosion cracking happens at nuclear plants.
Inconel 690 lasts a long time when used in places where highly toxic chemicals are present. If your product has moderate corrosive conditions and temperature cycling, Inconel 600 will protect you at a lower cost.
High Temperature Performance and Oxidation Resistance
Both metals keep their structural integrity at high temperatures, but they react to oxidation in very different ways. Because it is made up of a lot of chromium, the Inconel 690 tube performs well in high temperatures when there are acidic atmospheres.
When you test oxidation at 1000°C, it shows that the performance is different in many ways:
Inconel 690 Information on High Temperatures:
- At 1000°C, the rate of oxidation is 0.02 mg/cm²/hour.
- Scale adherence: Great up to 1200°C
- Tensile strength retention: at 650°C, it was 85%.
- Creep resistance: Better over 700°C
- Inconel 600, for High Temperatures Information:
- At 1000°C, the rate of oxidation is 0.08 mg/cm²/hour.
- Scale adherence: Up to 1000°C, it's good.
- Tensile strength retention: 80% at 650°
- Creep resistance: Good up to 650°C
Inconel 690 has more chromium in it, which makes a more stable oxide layer. This protective barrier holds up during thermal cycling processes. Extended testing of scale formation shows better adherence compared to Inconel 600.
If your product needs to work above 800°C all the time, Inconel 690 is better at resisting oxidation. If you need to stay below 700°C most of the time, with only short peaks above, Inconel 600 will work just fine.
Mechanical Properties and Strength Characteristics
The way a material reacts to being stretched, bent, or otherwise forced to change shape is an important part of choosing a material for structural uses. Both metals keep their great strength at high temperatures, but small differences make one more suitable than the other for certain situations.
At-Room-Temperature Comparison of Mechanical Properties:
| Property | Inconel 690 | Inconel 600 |
|---|---|---|
| Yield Strength | ≥ 275 MPa | ≥ 240 MPa |
| Tensile Strength | ≥ 655 MPa | ≥ 550 MPa |
| Elongation | ≥ 30% | ≥ 35% |
| Hardness (HB) |
|
150-220 |
The room temperature tensile strength of the Inconel 690 tube is about 20% higher than that of Inconel 600. This strength benefit holds true across the entire range of working temperatures, which gives the structure more strength.
Fatigue testing shows that Inconel 690 has much higher endurance limits when loads are applied and removed repeatedly. The better grain boundary chemistry lowers the number of places where cracks can start during stress cycle operations.
Inconel 690 is the best choice for pressure vessels when you need to make sure that your structure is as strong as possible. If you value flexibility and formability in your design, you should use Inconel 600 because it is easier to work with.
Nuclear Industry Applications and Steam Generator Performance
The nuclear power business is the most important field that uses these alloys in different ways. Choosing the right steam generator tubes has a big effect on how reliable and long-lasting a power plant is overall.
Inconel 690 tubes for steam generators work extremely well in pressurized water reactors. The alloy's resistance to primary water stress corrosion cracks almost completely stops the ways that tubes made of older materials break down.
Here's what we've learned from operating nuclear ships around the world:
- No cases of stress corrosion cracks in Inconel 690 tubes that were properly heat-treated
- Operational lifespans over 60 years in steam engine service
- Lower upkeep needs than Inconel 600 installations
- Better resistance to wear from grinding and denting
The nuclear industry use of the Inconel 690 tube is based on thorough qualification testing and operational validation. Based on a lot of information about how well it works, people who work in nuclear safety around the world have decided that Inconel 690 is okay to use for very important nuclear uses.
Inconel 600 was traditionally used in steam generators but was found to be prone to stress corrosion cracking. This is fine for some nuclear uses, but it needs regular checks and careful control of the water chemistry.
If you are designing nuclear steam engines that need to work for 60 years, Inconel 690 is the most reliable material. If your use of nuclear systems is less important and upkeep can be done regularly, then Inconel 600 is still a good choice.
Welding and Fabrication Considerations
Welding traits have a big effect on how easy it is to make something and how reliable the joint is. Both metals need careful attention when welding, but they act differently in some ways.
It is helpful for Inconel 690 tube welding methods to have less carbon because this lowers the risk of carbide precipitation. The alloy can be easily welded using both gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW).
Important welding settings for the best results:
- Before heating, set the setting between 200°C and 300°C for parts that are thicker than 25 mm
- Interpass temperature: no more than 350°C to stop grain growth
- After-weld heat processing: At temperatures between 1040 and 1080°C, solution heating
When welding Inconel 600, it is important to control the heat flow carefully because it is more sensitive to heat than other materials. It is easier for carbide to form in the heat-affected zone, especially when there is more carbon.
The reaction of the Inconel 690 tube to heat treatment gives better stability to the microstructure after welding. Carbides are successfully dissolved and corrosion resistance is improved by solution annealing.
If your production includes a lot of welding, Inconel 690 has better weldability and heat treatment response. If your project only needs a little bit of welding and the process needs to be carefully monitored, Inconel 600 is a good choice for how to make it.
Cost Analysis and Economic Considerations
Along with how well the material will work, economic factors also play a role in choosing a material. Understanding how costs vary helps get the most out of a project budget while still meeting performance standards.
Because it has more chromium and needs to be processed in a certain way, Inconel 690 usually costs 15% to 25% more than Inconel 600. But when you look at the costs over the entire lifecycle, it often turns out that Inconel 690 is better for difficult uses.
Total cost of ownership:
- Initial high cost of materials
- Lowered how often repair needs to be done
- Longer working lifetime
- Lower chance of being replaced
- Better system dependability
It costs hundreds of millions of dollars to repair nuclear steam generators. Inconel 690 tubes are more reliable, so the material cost is worth it because it avoids downtime costs and makes the working life longer.
Chemical processing uses the same technology, which is good because it needs less upkeep. Better corrosion protection means that inspections can happen less often and there are fewer unplanned shutdowns.
If you need your application to be super reliable with not a lot of upkeep, Inconel 690 gives you the best value over its lifetime. If you want to minimize costs up front and are okay with upkeep intervals, Inconel 600 is a good choice because it performs well and is affordable.
Conclusion
You need to consider your application's needs and the way it will be used when deciding between Inconel 690 and Inconel 600 tubes. Inconel 690 has better corrosion resistance, better performance against oxidation at high temperatures, and better resistance to stress corrosion cracking because it has more chromium than Inconel 625. Because of these benefits, it's perfect for nuclear steam generators, harsh chemical processing, and other uses that need to work at very high temperatures.
Inconel 600 is still a good choice for places that aren't very corrosive, as its lower cost and decent performance fit project needs. Knowing these important differences helps you choose the right materials that will work well and save money for your individual application needs.
TSM Technology's Premium Inconel 690 Tube Solutions
With 14 years of experience working with superalloys, TSM Technology provides outstanding Inconel 690 tube manufacturer options. Our state-of-the-art manufacturing tools make sure that the quality and performance of your most demanding uses are always the same.
Inconel 690 tubes from TSM Technology have some important benefits:
- A very modern factory with 8 production lines just for this purpose and over 100 precision tools
- Impressive supply ability of 300 tons per month, which makes sure that shipping times are always reliable
- A wide range of sizes: 6.0-114mm outer diameter, 0.5-15mm wall thickness, and lengths as long as 15,000mm
- Many ways to treat the surface, such as grinding, electropolishing, and chemical passivation
- Finish meeting the requirements for approval according to the ASTM B622, ASME SB622, and EN 10095 standards
- MTC and SGS test records for every shipment show strict quality control
- The ability to custom make and handle things according to your needs
- ISO 9001 and AS9100D standards show that we are dedicated to high-quality work
- Global reach with full logistics help for over 70 markets
- Expert help from materials engineers who know a lot about high-temperature metals
- A competitive price that works well for both small and large sales is well organized
- The more advanced ways of doing ultrasonic testing, radiographic checking, and eddy current testing
- Comprehensive material traceability ensuring full record for important uses
- The ability to speed up processes for project needs that are time-sensitive
- Work that is still going on to research and create superalloy technology
Our new 50,000-square-meter factory uses the most advanced technology to make tubes with perfect accuracy. Five-axis machining centers and CNC tools make sure that they are dimensionally correct within the tightest margins for aerospace, nuclear, and chemical processing uses.
Our engineers work together with your technical staff to get the job done, whether you need standard setups or one-of-a-kind unique solutions. We know how important your applications are, and we give you tools that will help you do even better than you expected.
Are you ready for the change TSM Technology makes in making superalloy tubes? Our knowledgeable sales team is ready to talk about your needs and give you full technical information. Emailing us at info@tsmnialloy.com is a great way to learn more about how our high-quality Inconel 690 tubes can help your project succeed.
References
American Society of Mechanical Engineers. "ASME Boiler and Pressure Vessel Code, Section II: Materials Properties for Nickel-Chromium Alloys." 2023 Edition.
Nuclear Regulatory Commission. "Steam Generator Tube Integrity and Assessment Guidelines for Inconel 690 Applications." NUREG-1801, Revision 3.
ASTM International. "Standard Specification for Seamless Nickel and Nickel-Chromium Alloy Condenser and Heat Exchanger Tubes." ASTM B622-22.
Electric Power Research Institute. "Materials Reliability Program: Inconel 690 Steam Generator Tube Performance Assessment." Technical Report 3002011809.
International Atomic Energy Agency. "Assessment and Management of Ageing of Major Nuclear Power Plant Components Important to Safety: Steam Generators." IAEA Safety Reports Series No. 15.
NACE International. "Corrosion Performance of Nickel-Chromium Alloys in Chemical Processing Environments." Publication 3A194, Materials Performance Studies.
