Osprey® MAR 55 tool steel eliminates the choice between weldability and performance

Seco is a leading global provider of metal cutting solutions for indexable milling, solid milling, turning, hole making, threading and tooling systems. For nearly 100 years, Seco has driven excellence throughout the entire manufacturing journey, ensuring high-precision machining and high-quality output. The R&D department that Ingemar Bite runs is always looking for ways to improve its products and make the best use of additive manufacturing (AM) technology.

Ingemar, what is your overall experience of using MAR 55?

"To me, MAR 55 is the material with the most interest and attention today. It has now, after evaluations and extensive testing, also been implemented in our production. We have used it both for prototyping and field testing, but now also for products that are today running in our customers’ production."

Ingemar Bite, R&D manager for Method Development at Seco.

"We are working a lot with AM hybrid technique, where it is crucial to have good mechanical properties and wear resistance already in the as-built condition. The conventionally produced pre-machined backends, which we weld our AM part on, would distort in shape if heat treatment is applied.”

This makes it ideal for tooling applications that require hardness levels above 50 HRC and wear resistance exceeding that of the 18-Ni class of maraging steels.

Faraz, you designed this new alloy. What was the idea behind it?

“One of the most common products for laser additive manufacturing is 18Ni300. It offers good printability but has some limitations such as low thermal stability and conductivity compared to carbon-bearing steels. MAR 55 was developed with these limitations in mind, offering a solution yet maintaining equally good printability as that of 18Ni300.”

Osprey® MAR 55 is primarily designed for excellent PBF-LB processability without the need for plate preheating. This makes it ideal for tooling applications that require hardness levels above 50 HRC and wear resistance exceeding that of the 18-Ni class of maraging steels.

Faraz Deirmina, Principal Metallurgist at Sandvik and the designer of Osprey® MAR 55.

It could be considered for applications including tooling, armor, shafts and fasteners as well as structural components. The exceptional fracture toughness at ultrahigh strength levels paves the way for the use of the tool steel in defense and aerospace.

What key benefits have you experienced when working with MAR 55 in Seco so far, Ingemar?

“Tests show that the fatigue strength is on a similar level as for materials used in our products today, which brings confidence to AM in general as a process. It also comes with a higher hardness and wear resistance than for example 18Ni300 or MAR60 do without heat treatment, as well as better corrosion resistance. All this, in the as-built condition.”

It bridges the gap between maraging steels and carbon-bearing tool steels. This means that the alloy is easily weldable, with exceptional toughness.

Are there other reasons behind MAR 55 becoming a popular solution with customers so quickly, Faraz?

“Yes, I believe it is because before MAR 55, customers had to choose between good weldability from carbon-free maraging steels and hard-to-weld, high-strength and high-wear-resistance carbon-bearing steels.

This new alloy is designed in such a way that customers no longer need to choose. It bridges the gap between maraging steels and carbon-bearing tool steels. This means that the alloy is easily weldable, with exceptional toughness. Also, it can be heat treated without the need for prior costly solution annealing (austenitization) or cryogenic treatments. At the same time its wear and fatigue resistance are similar to the carbide-strengthened, tempered martensitic microstructures of medium carbon tool steels.”

Powder metallurgy in general is considered a green technology since it reduces material losses and CO2 emissions in manufacturing compared to conventional manufacturing. Sandvik’s expertise in utilizing recycled materials contributes to even more significant sustainability in view of emission and energy consumption factors being reduced by over 50% in manufacturing of gas-atomized maraging steel powder.

How about sustainability Faraz, are there any attributes of MAR 55 that can help customers reach their goals in this area?

“Yes, when compared to 18Ni300, the content of both nickel and molybdenum is reduced by 50%. The leaner composition in MAR 55 significantly reduces both energy and emission factors.

Using the emission factors and nominal chemistries for both alloys there is a reduction of 21% in embedded CO2 (emission factor tCo2/t) and a reduction of 26% in embedded energy (KWh/kg) for the raw material makeup in MAR 55 versus 18Ni300. This is based on nominal embedded energy factors for virgin materials. If recycled raw materials are used, then energy and emissions are further reduced.

Moreover, customers (Seco included) are confirming a longer service life using MAR 55 compared to 18Ni300. Higher longevity of the components before repair or replacement is needed to help customers achieve their sustainability goals.”

Facts

Main characteristics of Osprey® MAR 55

• Processability: Excellent processability by laser powder bed fusion and laser directed energy deposition without the need for plate or platform preheating
• Chemical composition: Optimized for excellent weldability similar to maraging steels while showing improved wear and fatigue resistance similar to carbon-bearing tool steels
• Thermal conductivity: Higher thermal conductivity compared to maraging steels and martensitic stainless steels
• Hardness and toughness: Exceptional hardness/toughness combination in as-built and heat-treated condition, exceptional toughness at cryogenic temperatures

Osprey® MAR 55 is designed for use in

• Additive Manufacturing (AM)
• Cold spray
• Hot Isostatic Pressing (HIP)
• Metal Injection Moulding (MIM)
• Micro-MIM
• Sintered metal filters and foams

Osprey® MAR 55 is produced in Sandviken, Sweden, in the VIGA plant to ensure low oxygen and contamination levels. Sandvik has a patent pending for the alloy.