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Investigation of processes during sintering of hardmetal by means of thermal analysis

: Gestrich, T.; Jaenicke-Roessler, K.; Leitner, G.

European Powder Metallurgy Association -EPMA-:
PM in Belgium, a crossroads in industry development. Vol.1: Hard materials : Euro PM 2006 Congress & Exhibition, 23 - 25 October 2006, Ghent, Belgium. Proceedings
Shrewsbury: EPMA, 2006
ISBN: 1-89907-232-2
ISBN: 978-1-89907-232-3
European Congress and Exhibition on Powder Metallurgy (EURO PM) <2006, Ghent>
Fraunhofer IKTS ()
experimentelle Untersuchung; Pulversintern; WC=Wolframcarbid; Cobalt; Feinkorn; Paraffinwachs; Entwachsen; Ausgasen; thermogravimetrische Analyse; Massenspektrometer; Dilatometrie; Gewichtsverlust; Eutektikum; Schmelzen; chemische Reduktion; Kohlenmonoxid; Kohlendioxid; Wolframoxid; Korngröße; Kohlenstoffgehalt; Temperatureinfluß; Längsschrumpfung; Schmelzschrumpfung

Most important processes during the heat treatment of hardmetal mixtures are drying, dewaxing, outgassing, melting of the metal binder phase and sintering. Methods of thermal analysis (thermodilatometry, thermogravimetry, differential scanning calorimetry, and mass spectrometry) are used for understanding these processes. Changes in the gas phase composition during the heat treatment (including pressure changes) result in changes of temperature ranges for phase transformations and reactions, kinetics, mechanisms of gas reactions and the carbon balance of the hardmetal mixture. The carbon balance which is very important for a high product quality and grain growth inhibitors influence the sintering behaviour and the melting of the metal binder phase. Thermal analysis describes experimental the interactions between gas and hardmetal mixture (for instance reactive gases like H2, CH4, CO, H2O, CO2, O2) and the effect of gas pressure or inert gases (Ar, He). The achieved process knowledge enables hardmetal producers to keep reproducible quality, to improve the control of the carbon balance, to reduce tolerances and scrap.