• PDF / 1,280,374 Bytes
• 11 Pages / 593.972 x 792 pts Page_size
• 51 Downloads / 213 Views

DOWNLOAD

REPORT

---

ER metallurgy (PM) is a cost-effective process used, e.g., for manufacturing near net-shape metallic products by die pressing metal powder into the desired shape and then consolidating the material by sintering at elevated temperatures. However, in the last years, the increasing cost and volatility in prices of the most common alloying elements in low alloy sintered steels (Cu, Ni, Mo), have been the motives for research into new alloying alternatives. Cheaper and more efficient alloying elements are Cr, Mn, and Si, widely used in the production of wrought steel parts. However, these elements present much higher affinity for oxygen than the traditional alloying elements. This is a very important limitation for the PM technology since the high

RAQUEL ORO, formerly with the Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Legane´s, Madrid, Spain, is now Post-doctoral Researcher, with the Chalmers University of Technology, Ra¨nnva¨gen 2A, 41296 Gothenburg, Sweden. Contact e-mail: [email protected] MO´NICA CAMPOS, Docent, is with the Universidad Carlos III de Madrid. CHRISTIAN GIERL-MAYER, Senior Researcher, and HERBERT DANNINGER, Full Professor, are with the Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164-CT, 1060 Vienna, Austria. JOSE´ MANUEL TORRALBA, Full Professor, is with the Universidad Carlos III de Madrid, also with the IMDEA Materials Institute, c/Eric Kandel, 2, 28906 Getafe, Madrid, Spain. From 12th January 2015, Raquel de Oro Calderon will be at Vienna University of Technology. Manuscript submitted March 24, 2014.@ Article published online December 25, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A

specific surface area available in the powder particles makes them more reactive in contact with the surrounding atmosphere and complicates the elimination of the natural oxides covering the powder particles. A possible way for avoiding oxidation is to introduce these elements combined (i.e., alloyed) with other elements with a lower affinity for oxygen (for instance Fe).[1,2] In such way, the chemical activity of the oxidation-sensitive elements can be significantly reduced. This is the case with fully prealloyed iron powders. Cr and Mn have been so far introduced in sintered steels by the prealloying route, and the characteristic oxidation/reduction stages taking place during the sintering process have been defined by the proper combinations of thermal analyses and degassing experiments.[3–6] In case of CrMo prealloyed iron powders, this type of studies have been the key point for adapting the sintering procedures to the specific behavior of these materials which nowadays are being sintered successfully in the industry. Besides the prealloying route, another interesting approach is the master alloy concept. A master alloy can be defined as a powder with a high concentration of alloying elements designed to be mixed with an iron base powder and provide the desired final composition during the sintering cycle. This concept was first introduced in the 70s wit