This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This Small Business Innovation Research(SBIR)Phase II project seeks to overcome the principal impediments of the inconsistent quality of metal matrix composite (MMC) materials from fly ash and aluminum. This project utilizes highly processed ash derived ceramics (ADC) as a reinforcing phase in aluminum MMCs manufactured with powder metallurgy (P/M) methods. The processed ADC has a narrow size distribution and is free of carbon, magnetite, and cenospheres. In powder metal technology the ADC alters the strength, stiffness, and hardness of the aluminum. When blended with aluminum powders and compacted into parts, aluminum MMC materials can be fabricated with stiffness properties like ductile iron. Sintering parameters can be manipulated to control the aluminum-ADC reaction and the silicon metal and spinel that it generates, thus creating wear resistance and hardness. The MMC then behaves like a hypereutectic alloy. The primary objective of this project is to formulate one or more high performance ADC-aluminum MMCs that are ready for commercial deployment. Achieving this level of performance will allow ADC?aluminum MMCs to compete directly with hypereutectic alloys and ductile iron in the production of parts for the transportation industry.
The broader impact/commercial potential of this project will be the ability to derive high quality, ash derived ceramics (ADC) that are recovered from coal combustion ash for use in new light weight high strength composite materials. These materials are needed in the transportation industry where weight, cost, and performance are critical. ADC-aluminum metal matrix composites can be used to manufacture parts for the transportation industry such as brake rotors, and drive train components that are currently made from ductile iron or hypereutectic alloys, materials that are heavier and/or difficult to machine. This material change will decrease the overall weight of the vehicle, thereby improving its fuel efficiency and performance while improving the margins for parts manufacturers. This technology will create a new commodity that will lead to the creation of new jobs and help support the needs of the automotive and transportation industries.
For this small business innovation research project, NuForm Materials utilized highly processed ceramic materials that we recycled from discarded coal combustion fly ash as an additive in metal parts fabricated with powder metallurgy. Our company uses patented technology to separate fly ash particles into groups according to size. The ceramics that are recovered, named ReNu Ceramics, are hard, spherical particles that are lighter than metals. During this project, ReNu Ceramics were added to aluminum alloy, bronze alloy, brass, and iron alloy powders to improve the hardness, strength, and, ultimately, the wear performance. Improved wear performance leads to extended life for the part. Further, the composite part would be lighter and less expensive than competing products already on the market. These characteristics meet the needs of several manufacturing markets, but especially the automotive, aerospace, and consumer goods industries. During this project, our company fabricated hundreds of test coupons from metal powder blends containing ReNu Ceramics. We incorporated the techniques of powder metallurgy (a popular manufacturing technique)—powder blends were compressed in a die and, subsequently, the pressed part was sintered, or heated above the softening point of the metal in order to promote bonding between particles. Each test coupon was tested for dimensional stability, hardness, and strength. Additionally, select test coupons were further analyzed using metallography—microscopic structure and elemental positioning were observed. An array of materials (lubricants, flux materials, etc.) was also studied as a means of optimizing the performance of the test coupons. The results from this effort showed some improvements; however, the overall goal of supplanting existing materials was not achieved during this period. Improvements in the hardness of test coupons were a regular occurrence; improvements in strength were rarer. Through metallography, we determined that the interfacial bonding between the ReNu Ceramics and the metal particles was underdeveloped, if present at all. The interface is critical for improved performance in the composite materials. In other words, the ReNu Ceramics were contributing very little to the overall performance of the part in some cases. We concluded that the ReNu Ceramics were not softening during sintering; therefore, the opportunity for bonding with the metal matrix was minimal. We worked with Symmco Inc., a manufacturer and distributor of self-lubricating bronze bearings, to develop a new, high performance material that contained ReNu Ceramics. We achieved partial success with both improved hardness and favorable strength with their bronze alloys. Prototype bearings were fabricated and tested on a custom wear tester. However, during the prototype tests, unbound ReNu Ceramics migrated into the bearing surface causing heat spikes and premature failure. These results further reinforced our belief that interfacial bonding was underdeveloped. Although our work with powder metallurgy produced results that were less than desired, we were able to develop a new technology for the utility industry that can solve a growing problem. As we processed coal combustion ash to generate ReNu Ceramics, we learned of developing problems with handling and disposing of coal combustion byproducts, including fly ash. Currently, the Environmental Protection Agency is deciding on new rules and regulations regarding coal combustion byproducts. Inevitably, existing ash retaining ponds and associated handling processes will be eliminated. We discovered during this project that our technology used for producing ReNu Ceramics could be modified to address the growing concerns over ash handling. Simply put, our technology can de-water and thicken fly ash as it leaves the power plant in existing pipelines. The processed ash can be deposited in a landfill and the clarified water can be recycled into the plant or passed through water treatment. This technology, which is efficient and cost effective, will solve the utility’s problem of converting from wet handling to dry handling systems (which involves major capital cost), converting from coal to natural gas as a fuel source (which also involves major capital cost), or closing the power plant. We are currently marketing this process to several utility companies.
