Alleima (formerly Sandvik Materials Technology)
Nickel alloys will most of the time outperform stainless steels when it comes to corrosion resistance over a wide range of temperatures. However, the superiority in performance comes with a hefty price tag. That is why Alleima R&D has come up with an innovative material solution, which bridges that gap between stainless steels and nickel alloys, i.e., achieving high performance, high strength, and superior corrosion resistance while maintaining cost-efficiency. Sanicro® 35 (UNS N08935) is an ideal material for industries and applications for the pipe and tube market used in demanding environments such as hydraulic and instrumentation, heat exchangers, Maritime, and Oil & Gas.
Sanicro® 35 is a newly developed material that earned its development team the Sandvik Innovation Prize in 2019. It also won the materials design category in the MP Corrosion Innovation of the Year Awards 2021. These awards are testaments to the material’s exceptional performance, high strength, and superior corrosion properties over a wide temperature range.
Introducing Sanicro® 35, a new member of the Sanicro® family by Alleima.
Sanicro® 35 is a special alloy that exhibits properties corresponding to highly alloyed nickel-based materials but with a significant cost advantage. It is a super-austenitic grade designed particularly for corrosive environments and seawater applications. The new alloy (UNS N08935) has a nominal chemical composition of 27%Cr-35%Ni-6.5%Mo-0.3%N, as shown in Table 1 below.
Table 1. The nominal chemical composition for Sanicro® 35.
Chemical composition (nominal) weight%
Given the various corrosion risks, such as pitting and crevice corrosion, it is vital to use materials that can resist corrosion under different harsh corrosive conditions.
Austenitic stainless steels, for instance, can become susceptible to corrosion under extreme conditions. For that reason, Sanicro® 35, a super-austenitic stainless steel, was designed to exhibit improved corrosion resistance and higher strength than common austenitic alloys. A super-austenitic alloy with a chemical composition containing high levels of molybdenum, nitrogen, and nickel content with a stable structure.
Duplex stainless steels exhibit higher strength but are limited in their working temperature range. This limitation is due to their ferrite phase, which becomes unstable at high temperatures and cause embrittlement, deteriorating the material’s mechanical properties.
These material groups leave a gap to be filled between them and the nickel-based alloys in terms of corrosion resistance and temperatures. This is where Sanicro® 35 fulfills its purpose.
Alleima developed Sanicro® 35 to bridge the gap in the market between stainless steels and nickel-based grades. This alloy is characterized by its excellent corrosion resistance (pitting, crevice, stress-corrosion cracking, erosion, and uniform corrosion), enabling its use in seawater applications and highly corrosive environments. This makes Sanicro® 35 a high-performance alternative to existing austenitic stainless steels, duplex stainless steels, and nickel alloys. The illustration in Figure 1 below provides a visual representation of where Sanicro® 35 fits among other materials.
Figure 1. A corrosivity vs temperature illustration showing the placement for super-austenitic Sanicro® 35 and how it is bridging the gap between austenitic stainless steels, duplex stainless steels and nickel base alloys.
Sanicro® 35’s key advantages are found in its outstanding corrosion resistance behavior, including pitting corrosion and crevice corrosion.
Pitting is a local form of corrosion where a “corrosion cell” is formed between a local point and the neighbouring surface. This creates a small pit in the surface, which gradually grows into a bigger cavity. Pitting corrosion is one of the most common corrosion failures in high-demand applications.
Pitting resistance is characterized by a pitting resistance equivalent number (PREN), which is defined based on the material’s chemical composition, particularly its chromium, molybdenum, and nitrogen contents. A higher PRE number is a theoretical indication of better pitting corrosion resistance.
PREN = %Cr + 3.3 × %Mo + 16 × %N
With a PREN of 52 and a critical pitting temperature (CPT) of over 85 °C, Sanicro® 35 borders nickel-based alloys in pitting resistance, such as Alloy 625 and C-276. It also shows superiority over super-duplex and austenitic alloys, such as 6Mo grade with PREN of ~42.5 and CPT of 65 °C.
Crevice corrosion is another localized form of corrosion that takes place in narrow gaps where oxygen flow is limited. These are areas of metal-to-metal contact or metal-to-nonmetal contact, such as underneath fasteners, bolt heads, gaskets, and washers. Such areas are referred to as dead spots, as liquid flow is reduced and restricted.
Test results from the ASTM G48 method F testing have shown a significant advantage in crevice corrosion for Sanicro® 35 over nickel-based Alloy 625, with critical crevice temperatures (CCT) of 45 °C and 25 °C, respectively. It also showed similar performance compared to Alloy C-276. Table 2 presents the CCT results for the alloys Sanicro® 35, Alloy C-276, Alloy 625, and Sandvik 254 SMO (6Mo).
Table 2. CCT results of ASTM G48 method F testing of Sanicro® 35 against other alloys.
Critical crevice temperature (CCT)
Sandvik 254 SMO
For more details on such tests and other corrosion properties, check out the technical properties in Sanicro® 35’s technical datasheet.
In addition to its excellent corrosion resistance, Sanicro® 35 delivers high mechanical properties and excellent structural stability over a wide range of temperatures.
Most notably, it has a yield strength of 425 MPa at room temperature (RT), significantly higher than the yield strength of Alloy 625 (276 MPa at RT), Alloy C-276 (283 MPa at RT) and 6Mo (310 MPa at RT). Sanicro® 35 also exhibits an elongation of 35% sustained even at elevated temperatures.
For more information on its properties, check out the technical properties in Sanicro® 35’s technical datasheet.
Not only does Sanicro® 35 have high mechanical strength and corrosion resistance, but it also exhibits good weldability. The recommended welding process is TIG welding (GTAW) using nickel alloy UNS N06059 as a filler metal.
Sanicro® 35 also has outstanding formability, which allows cold bending into a tight bending radius, not limiting your design.
Such an innovative alloy has an amazing potential to be a material of choice for pipes and tubes used in applications with corrosive environments, such as seawater applications, the Oil&Gas industry, heat exchangers, and hydraulic and instrumentation tubing.
In fact, due to Sanicro® 35’s excellent mechanical properties, engineers can use tubes with thinner wall thickness, which can result in better heat transfer. Being a material with versatile properties, Sanicro® 35 can be your “all-in-one” instrumentation tubing grade, able to replace alloys like 6Mo, Alloy 625, Alloy C276, and Alloy 825.
Alleima has been providing innovative solutions and products for over 150 years, with materials ranging from stainless steels to special alloys, titanium, and other advanced materials. Today, Alleima has partnered with Matmatch to bring its advanced materials one step closer to engineers and product developers in search of engineering solutions. With their range of materials now found on Matmatch, you can explore, compare, and select the right material for your project.
For more specification-related questions, visit Alleima’s product portal, where you can learn more about Sanicro® 35, request the complete datasheet, and find all related information.
Advancing industries through materials technology
We are Alleima (formerly Sandvik Materials Technology).
Here to advance industries through materials technology. Our development and manufacturing of advanced stainless steels and special alloys are world-leading. It’s what we’ve been doing for over 160 years, and it’s still our reason to exist. Fueled by our desire to care, deliver and evolve, we benefit our customers, our people, and the future we share. And it’s how we relentlessly push products and processes to be more efficient, more profitable, and more sustainable.
With close and long-standing customer partnerships, we advance processes and applications in some of the most demanding industries imaginable. Our passion for materials technology, metallurgy, and industrial processes helps customers become more efficient, more profitable, more sustainable, and safer.
Our business concept is to be the world's leading provider of advanced stainless steels and special alloys as well as products for industrial heating – without compromising our goals in sustainable development.
Our high value-added products and services are aimed at helping our customers fulfill – and even exceed – their productivity and performance expectations. In creative partnerships, we develop innovative solutions designed to pave the way to their success.
We offer a wide range of highly engineered products based on an integrated production platform and extensive R&D as well as premium standard products.
Based on decades of materials expertise and application knowledge our products and services contribute to improved productivity, reliability and cost efficiency while often reducing the environmental impact in a wide variety of industry segments.
Strong foundation for continued success
Our origins date back to 1862, our operations have been based on product innovation, technology leadership and close, long-term customer relationships. This approach is still the cornerstone in our endeavor to reach our vision – to set the industry standard in the areas in which we operate.
Our operations are based on unique expertise in materials technology and extensive insight into industrial processes and applications. This combination has resulted in proven capabilities to optimize customer productivity.
Having the right combination of academic qualifications and hands-on experience, we work closely with our customers to jointly discover ways of addressing their challenges. Our various collaborations with leading research centers and universities worldwide, contribute to new or further developed technologies for increased customer value.
USE. REUSE. REPEAT.
THAT’S SUSTAINABLE STEEL.
Your sustainability goals are our goals, too. Our aim is to lead the ongoing shift in our industry and earn your trust as a true partner when it comes to innovative materials solutions.
To achieve this, we’ve set four sustainability goals for 2030, in line with the UN’s Sustainability Goals and the Paris Climate Accord. They guide all aspects of our approach to steel- making, including the products and services we offer.
OUR SUSTAINABILITY GOALS FOR 2030
For us, a sustainable steel process means that we re-use the steel over and over again. We also rely on highly efficient processes powered by a mix of fossil-free, carbon-reduced or our own residual energy sources. Examples from our mill in Sandviken, Sweden include: