Sintering iron using a hollow cathode discharge

Abstract

Unalloyed iron samples were sintered in the presence of a hollow cathode glow discharge, generated in a gas mixture of 80% Ar+20% H 2 at pressures ranging from 133 to 400 Pa. The sample, which worked as the inner cathode of the discharge, was heated by the bombardment of strongly accelerated ions and fast neutrals created in the cathode sheath. The outer cathode of the hollow geometry consisted of a stainless steel AISI 310 cylinder. The enhanced ionization obtained in the hollow cathode configuration provided a high current density (25 mA cm −2) and consequently a high temperature could be attained (1250 °C). The samples were sintered at 1150 °C for times ranging from 30 to 240 min. The temperature was adjusted by varying the time on/off of the pulsed power supply used to generate the discharge. Microstructural results are presented and it is shown that samples may be successfully sintered in a hollow cathode discharge. In addition, atoms of Cr and Ni sputtered from the outer stainless steel cathode were deposited onto the sample surface and diffused, during sintering, resulting in the formation of a layer approximately 20 μm thick containing these elements.