Sinterizazio-atmosferaren eragina M graduko (ASP 30 ... - Euskara

INTRODUCTION
Work carried out in the last two decades on the sintering of high speed
steel powders has allowed obtaining high density components with near net shapes .
One of these routes is direct sintering, consisting of cold compaction of annealed
water atomized powders and subsequent vacuum sintering to full density . This
technique has been successfully applied to T1(1), M2(1), T6(2), T42(3,4), T15(5)
and M42(6) .
Recent work in CEIT has shown an alternative route to the vacuum
sintering, reaching theoretical densities by sintering in a flowing atmosphere of N2-
H2-CH4 . Work has been performed on M2(7), T15(8), T42(9), T6(10), M42(11) and
Px30 (12) . This last technique (gas atmosphere sintering) allows continuous
sintering of near net shape compacted water atomized powders to full density at low
temperatures (12-14) and hence can offer innovative routes to the production of
several kinds of tools, dies and engineering components . Sintering of compacted
water atomized powders- in an atmosphere rich in nitrogen, as well as the
technological and economic benefits of allowing a continuous sintering -instead of in
closed batch-, decreasing the optimum sintering temperature and widening the
sintering gate (12-14) compared to vacuum sintering -as pointed above-, offers in
addition several benefits : microstructural control (finer grain sizes, finer carbonitrides
instead of massive carbides (12-14)) and improved mechanical properties (higher
hardness and toughness (15,16)) originating from the appropriated heat treatment
producing improved microstructures .
In -the present work_ the advantages of sintering - iñ -nitrogen rich gas
atmosphere compared with vacuum sintering are summarized . It is worth
emphasizing that the potential cost saving with low temperature atmosphere
sintering, and improvement in microstructure, mechanical properties and
performance in service, with the use of new heat treatments offers the prospect of
significant competitive advantage to manufacturers of tools and wear parts .
EXPERIMENTAL PROCEDURE
Vacuum annealed, water atomized T42, T15 and Px30 powders were
bought from Powdrex Limited, Tonbridge, U .K. The composition of the powders
provided by the manufacturer are given in Table I . Additions of 0 .2 weight % of