Northrop and Poland sign MoU on austempered ductile iron shells

Northrop Grumman has signed an MoU with Elaboracja Niewiadow (Grupa Niewiadów) with the intent to explore collaboration on the development of 155 mm artillery ammunition. Specifically, the two companies will focus on Northrop’s Austempered Ductile Iron shells, the September 18 press release states. 

The two companies will explore the possibility of Northrop Grumman delivering the 155 mm Austempered Ductile Iron shells to Elaboracja Niewiadow as well as assistance in development of 155 mm ammunition that meets the needs of the Polish armed forces. This will also include the potential for an update of facilities at Elaboracja Niewiadow that could produce Austempered Ductile Iron shells.

“We expect this MoU will help Poland establish a diverse supply base to meet the growing demand for artillery in Central and Eastern Europe. Our expertise with munitions and advanced manufacturing methods will allow the use of existing commercial facilities to increase supplies without adding strain to Poland’s defense industrial base,” Frank DeMauro, sector vice president and general manager, weapon systems at Northrop Grumman said in the press release. 

Poland is working to expand its munitions production across the board, including a partnership between the WB Group and Hanwha Systems to produce missiles for the Homar-K multiple rocket launchers. This agreement is seen as critical to Poland’s fielding of the Krab and K9 self-propelled howitzers. The country has ordered large fleets of these howitzers, with 364 K9s being delivered both from new production, South Korean stocks, and partnerships with Polish companies. There are also framework agreements and orders for at least 300 Krab howitzers. 

This impressive fleet will need a lot of ammunition to support its training needs and of course in the event of a war. “This MoU is crucial in rapidly developing 155mm ammunition for the Krab and K9 systems. At the same time, it expands our role far beyond national needs — positioning Poland as a key hub for advanced artillery ammunition within NATO,” Mirosław Klepaczewski, president of the management board at Elaboracja Niewiadów, said. 

Tech explainer: Austempered Ductile Iron shells

The microstructure of Austempered Ductile Iron. Note the large spherical graphite nodules and different grains of the material which give it its strength. Credit: LBoron Łukasz Boroń – Own work, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=84592273

Traditional artillery shells fired from a tube howitzer are made from steel. This is because they have to withstand the pressures imparted to them during firing and steel provides the requisite strength. However, it requires machine tooling and high cost materials to develop. Austempered Ductile Iron shells by comparison use cast iron that is given a unique heat treatment to achieve a level of strength and ductility comparable – and sometimes superior – to steel. 

Cast iron is typically quite fragile and prone to cracking, which makes it unsuitable for tube howitzers. Although, some mortar bombs continue to use it. However, iron can be made ductile through alloying with materials like molybdenum or nickel. The metal is then put through the austenitizing process, which includes the following steps: 

• Austenitizing: The ductile iron is heated to a high temperature (typically between 850°C and 950°C) to transform its structure into austenite.
• Quenching: The material is then rapidly cooled to a lower, intermediate temperature in a salt bath, which is held constant. This rapid cooling prevents the formation of unwanted pearlite or martensite.
• Austempering: The material is held at this constant temperature (usually between 250°C and 400°C) for a specific duration. During this time, the austenite transforms into the desired ausferrite structure, which is a mix of acicular (needle-like) ferrite and carbon-rich austenite.

The final material can be 10% lighter but as strong, or stronger than steel. It has good resistance to fatigue and impact, and is more cost-effective than steel. Austempered ductile iron has been used in the commercial sphere for digger teeth, gears, differentials, and in the rail industry for some time. But, Northrop Grumman states it has pioneered the use of the method in projectile production. And it now has a facility that can produce 50,000 tonnes of Austempered Ductile Iron shells per year. 

Calibre comment

A long, sustained war will often be decided by the industrial capacity of a nation to support and maintain it. This covers everything from the production of ammunition, vehicles, and equipment, through to the replenishment of lost forces. These are all aspects that Western countries have disinvested in since the end of the Cold War. This is an understandable development. Retaining spare capacity for ammunition production, for example, and large stockpiles of that ammunition, is enormously expensive. Russia, to some extent, was in a similar position in February 2022. But the war in Ukraine has forced its economy and defence industry to shift to a war-footing. It is now able to produce hundreds of missiles per year, and thousands of shells per day. For NATO to provide a real and credible deterrent, it will have to ensure that its military capability is backed up by industrial might. Partnerships like this between Northrop Grumman and Elaboracja Niewiadow will contribute to that credibility if they lead to meaningful increases in production. 

By Sam Cranny-Evans, published on September 22, 2025. Credit for the lead image is Grupa Niewiadów. It shows, from left to right, Mirosław Klepaczewski, president of management board, Elaboracja Niewiadów, Krzysztof Krystowski, Country Director, Northrop Grumman Polska S.A., Quinn Canole, Managing Director Northrop Grumman Polska S.A., as they participate in the MOU signing ceremony at Grupa Niewiadów.