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Technical Paper

P/M Ferritic Stainless Steels for Exhaust System Components

The advent of stainless steel automotive exhaust systems presents a significant opportunity for powder metallurgy (P/M) parts and the inherent economic advantages of this near net shape metalworking technology. A study was performed to determine the viability of ferritic P/M stainless steel parts for exhaust applications such as coupling flanges and hot exhaust gas oxygen sensor (HEGOS) bosses. In order to help achieve the automotive industry's stated goal of extending the functional life of exhaust components while remaining competitive, the authors developed a program to develop a database of the mechanical properties and performance characteristics of several grades of P/M stainless steel. Among the data generated and analyzed for these ferritic alloy systems are room temperature, tensile stress-strain curves, fatigue and endurance properties, hardness levels, and corrosion resistance.
Technical Paper

P/M Stainless Steels Applications in Automotive Exhaust Systems

Several applications for powder metallurgy (P/M) produced stainless steel exhaust components have been approved and are in production today. Many more stainless steel parts, both ferritic and austenitic, are in the final qualification stages. This paper will review the performance and economic criteria employed by automotive companies and exhaust manufacturers in sourcing exhaust coupling flanges and oxygen sensor bosses. Also, the performance record of the components in service to date will be reviewed. Finally, the advantages of P/M steel parts versus competing metal working industries (i.e. cold stamping, cold heading, screw machining) will be detailed.
Technical Paper

The Effect of Sintering Temperature and Flow on the Properties of Ni-Mo Steel Hot P/M Formed Material

Water-atomized nickel-molybdenum alloy (0.5 Ni-0.5 Mo) powder was blended with graphite for 0.4% carbon, then pressed into preforms (1.5 X 2 X 5 in). The preforms were hot formed to full density via a variety of processing conditions (various degrees of flow, sintering temperature, and sintering atmosphere). Impact specimens were excised and tested over a range of temperatures to determine the ductile-to-brittle transition temperature. All impact specimens had ductile failure at room temperature. In general, increased deformation increased the room-temperature and low-temperature impact strengths by eliminating particle boundaries and elongating the inclusions. High temperature sintering reduced the oxygen content and improved the impact strength by reducing the number of crack-initiating inclusions. Jominy hardenability test results were unaffected by various sintering conditions because the amount of easily oxidizable alloying elements was kept to a minimum.
Technical Paper

Newly Developed P/M Materials to Replace Malleable and Ductile Cast Irons

Malleable and ductile cast irons are used extensively in automotive applications such as clutches, gears, carriers, shafts, bearings, cam, racers, hubs, etc. Recently developed P/M materials can be processed cost efficiently to replace malleable and ductile iron castings. An UTS in excess of 1240 MPa and a YS in excess of 825 MPa can be achieved with one of these new materials. These tensile properties can be coupled with elongations over 2% and impact energies over 25 Joules. This presentation will cover processing routes for these new materials and will identify parts that may benefit from this new technological advancement.