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Oak Ridge National Laboratory (OPEN 2015)

ARPA-E Impacts: A Sampling of Project Outcomes, Volume III
Publication Date: 
Friday, January 19, 2018
Technical Areas: 


UPDATED: January 3, 2018 
PROJECT TITLE: New, High Temperature, Corrosion-Resistant Cast Alloys for Operation in Industrial Gaseous Environments
AWARD: $3,900,000
PROJECT TEAM: Oak Ridge National Laboratory (ORNL), University of Wisconsin – Milwaukee, Metaltek International, Duraloy Technologies, ArcelorMittal
PROJECT TERM: April 2016 – April 2019
PRINCIPAL INVESTIGATOR (PI): Govindarajan Muralidharan


Transporting and handling corrosive gases at high temperatures is ubiquitous in industrial chemical processing and power generation. Conventional metal alloys used for pipes and other equipment cannot survive such harsh environments. Austenitic steel, a type of stainless steel alloy commonly used in harsh environments, forms a chromia (Cr2O3)-scale oxide layer to help protect alloys from corrosion. However, the chromia protective layer can deteriorate in these environments, significantly reducing component lifetime due to corrosion, and reducing the energy efficiency of the processes that use the parts formed from this metal due to lower thermal transfer rates. Although chromium (Cr) metal is critically important to the energy efficiency of the U.S. industrial infrastructure, it is not available domestically. Therefore, the development of an alternative to chromia-forming alloys that uses lower amounts of Cr is of high importance to U.S. industry. Cast alumina-forming, nickel (Ni) base alloys are commercially available, but are quite costly due to the high levels of expensive Ni additions. Development of these lower-cost iron (Fe)-base alloys is critical for the U.S. manufacturing industry to be competitive in the global market.


One alternative to chromia-forming alloys is alloys that form alumina (Al2O3) as their protective surface layer in service. Alumina-forming alloys typically exhibit superior high-temperature corrosion resistance compared to chromia-forming alloys, primarily due to slower oxide scale-growth rate and greater thermodynamic stability at high temperatures (900-1200oC). Numerous attempts to produce Fe-base alumina-forming casting alloys on a commercial scale with the high temperature strength needed for structural use have failed because the added aluminum (Al) complicates the melt processing of large castings needed by industry. During melting, the Al added to steel reacts with nitrogen in the air to form coarse aluminum nitrides, which weakens the alloy resulting in unacceptable properties. This nitride formation also depletes the Al needed to form the alumina coating on the alloy surface that protects it from corrosion. Prior to this ARPA-E project, ORNL patented several new Fe-base austenitic alloy compositions with excellent creep resistance and alumina-forming capability at temperatures of 900-1100ºC.[1] This work was based on alloy production at a 100-500 gram size scale. In order to make this new alloy technology industrially relevant however, alloy development needs to be scaled to tons of production using methods that can be performed in a commercial foundry.  


This project aims to translate the laboratory development of ORNL’s patented alumina-forming austenitic casting alloys into industry-applicable materials that can survive industrial production practices and still operate in high temperatures and caustic environments. When they were devised at ORNL, these new alloys could be made under tightly controlled mixing, heating, and quenching conditions. These conditions cannot be duplicated at industrial scale without becoming cost prohibitive, so the original published formulations must be reengineered for manufacturability. Without this reinvention, these new materials will not transition from the lab to manufacturing. Because there are an extensive number of potential alloy combinations that require testing to determine the optimal alloy for a given use case, the ORNL team set out to investigate the properties of various alloy types to determine if any met the requirements of the steel industry. To date, the ORNL team has tested over 60 formulations of its alloys, and has down-selected the optimized versions for ton-scale production that provide the desired protection in high temperature and caustic environments. ORNL has been working with its partners to produce these alloys and the associated processing technologies necessary to use them industrially. ORNL is developing unique formulations that utilize the minimum amount of aluminum required for scale formation in the alloy (up to 4-5% by weight). The alloy is then stabilized with additions of niobium, titanium, zirconium, and other elements to prevent the formation of aluminum nitride during melting and to achieve the best properties in industrial use. ORNL is fabricating a prototype industrial component from one alumina-forming alloy with tenfold oxidation resistance and twice the resistance to “creep” (sagging under structural loads at high temperatures) compared to chromia-forming alloys, with functionality in excess of 1100ºC. This component is being compared to HP-type[2] cast chromia-forming austenitic steel and tested in an industrial environment. The ultimate goal is for these alloys to be produced at scale for the same cost, but last up to ten times longer, while maintaining the same creep life as austenitic steels. 


Figure 1: The new alloy developed by the ORNL team is up to 10x longer lasting than the industry standard alloy used for ethylene cracking furnaces.


This project united the material developer, ORNL, materials producers and component manufacturers, Duraloy Technologies and MetalTek International, and a potential end-user, ArcelorMittal. The team identified furnace rolls for steel production as the first application for the newly developed alloys. Furnace rolls (shown in Figure 2) are rotating pieces of a conveyor that move steel plates through an austenitizing furnace. These rolls experience drastic changes in temperature and stresses on a regular basis in an oxidizing environment that requires regular replacement. ArcelorMittal successfully began testing a prototype furnace roll (Figure 2) using a down-selected alloy in a 200-foot plate austenitizing furnace in April 2017. After 4,000 hours at 900ºC this trial roll was removed from the furnace for inspection, and was found to have no appreciable degradation. Under similar conditions, rolls of currently used commercial HP alloys, have to undergo periodic maintenance to remove oxide layers formed due to corrosion resulting in furnace downtime, loss of production, and ultimately, roll replacement. Additional sales of these new furnace rolls are anticipated in early 2018 based upon these initial trials.


Figure 2: Furnace roll made with the ORNL team’s alloy. This roll appears pristine after being in a plate austenitizing furnace at 900°C for 4000 hours. Compared to state-of-the-art alloy furnace rolls, the new rolls result in significantly lowermaintenance costs and improved productivity.


The high-temperature, corrosion-resistant alloy developed in this project will greatly increase the efficiency and longevity of equipment used in fossil fuel extraction, chemical processing, and transportation fuel production. The potential cost and energy savings are significant given the wide range of applications for this technology across the globe. The commercial availability of this alloy will enable disruptive improvements in energy efficiency for critical industry processes by increasing productivity, reducing costs, increasing equipment life, and decreasing process downtime.


The ORNL team has published the scientific underpinnings of this technology in open literature. A list of publications is provided below:

M. P. Brady, G. Muralidharan, Y. Yamamoto, B. Pint, “Development of 1100°C Capable Alumina-Forming Austenitic Alloys,” Oxid Met, Feb. 2017, Vol. 87, Issue 1, pp. 1-10. Feb. 2017.

G. Muralidharan, Y. Yamamoto, M. P. Brady, L. R. Walker, H. M. Meyer II, and D. N. Leonard, “Development of Cast Alumina-Forming Austenitic Stainless Steels” JOM, Vol. 68, Issue: 11, Pages 2803-2810, Nov. 2016.



Muralidharan 2013: G. Muralidharan, Y. Yamamoto, and M.P. Brady, US Patent 8,431,072 “Cast Alumina Forming Austenitic Stainless Steels” (April 30, 2013.); Yamamoto 2014: Y. Yamamoto, G. Muralidharan, and M.P. Brady, US Patent 8,815,146 “Alumina Forming Iron Base Superalloy” (Aug 26, 2014).

HP refers to a designation of stainless steel: Fe, 35Ni, 25Cr.