U.S. NETL Creates Tougher Steel Alloy Using Cerium

The addition of the rare earth element cerium is believed to be result in a tougher steel alloy for pipelines. Photo courtesy of NETL.

Structural materials engineers at the U.S. National Energy Technology Laboratory (NETL) are producing what they believe is a more robust pipeline material to transport hydrogen and captured carbon dioxide (CO2). According to NETL, the tougher steel alloy was formed using the rare earth element (REE) cerium.

The accomplishment simultaneously addresses two important U.S. Department of Energy priorities: developing infrastructure needed for decarbonization and improving the critical minerals supply chain.

NETL researchers say the added cerium reacts with oxygen and sulfur impurities that are introduced during steel manufacturing. In turn, this eliminates the negative impact of those impurities and produces a steel that is less susceptible to cracking during its service life. 

Testing at NETL has shown that cerium additions to X90 pipeline steel can improve the Charpy impact toughness—a measure of the steel’s ability to absorb energy and resist crack propagation—by up to 50%.

“Such an improvement is important for new pipelines, where running ductile fracture is a major concern, such as for carbon dioxide transport,” says Richard Oleksak, research scientist. “These results show promise, and more research is needed to determine the impact of cerium on other important steel properties such as weldability.” 

“Better steel isn’t the only potential benefit,” Oleksak adds. “Cerium, which is the most abundant rare earth element in both conventional and unconventional domestic feedstocks, is currently a major unused byproduct of the extraction of more valuable rare earths. This means we could see the creation of applications for cerium to meet industrial demand.”

Oleksak believes that with global steel production at 2-billion tons annually, the incorporation of even small amounts of cerium into industry would significantly increase its demand. By developing high-volume applications for cerium, the value proposition for domestic production of rare earths is improved. In turn, this should enhance the supply chain for these critical minerals, he says.

According to NETL, REEs have a long history in iron and steelmaking. Specifically, cerium, lanthanum, and cerium/lanthanum-rich alloys have been used in some form since the 1950s. The cost of cerium and lanthanum has decreased significantly since major work involving these elements was conducted in the mid-1900s in iron and steelmaking.

A major driver of this cost reduction is related to the so-called rare earth balance problem. That is, both cerium and lanthanum co-occur with other REEs, such as neodymium, in both conventional and unconventional domestic feedstocks. 

Because of the high demand of neodymium and other REEs for various clean energy technologies, and the likely increase in demand for these technologies in the era of global decarbonization, it is very likely that tremendous amounts of unused cerium and lanthanum will be produced in the coming decades.

“This presents an excellent opportunity for the renewed consideration of these rare earths as promising and inexpensive alloy additions in steelmaking,” Oleksak says. “The success of NETL in developing cerium-enhanced steel alloys is an example of the potential economic and environmental benefits to come from acting on such opportunities.”

According to NETL, significant new pipeline infrastructure improvements are expected within the coming years that can help facilitate U.S. decarbonization goals, including pipelines specifically designed for CO2 and hydrogen transport. Both uses pose unique challenges and place increased reliance on the integrity of steel products.

Source: NETL, netl.doe.gov