The use of low melting point master alloy (MA) powders contributes beneficially to sintering by increasing the distribution rate of alloying elements, enhancing homogenisation and sometimes also promoting densification. However, working with liquid phases poses important challenges like maintaining a proper dimensional control and minimising the effect of secondary porosity on the final performance of the steel. In this work, three different MA systems are compared: a low dissolutive Cu-based MA, and two systems with a higher degree of iron dissolution but different content in oxidation-sensitive elements. The combination of wetting experiments, step sintering tests and dilatometry studies show how the evolution of the microstructure, dimensional stability and overall densification are strongly affected by the characteristics of the liquid MA and in particular by its ability to dissolve the iron base particles, and by the amount of oxidation-sensitive elements present in the composition of the MA powder.
ZapfG. and DalalK.: ‘Introduction of high oxygen affinity elements manganese, chromium and vanadium in the powder metallurgy of P/M parts’, Mod. Dev. Powder Metall., 1977, 10, 129–152.
2.
HoffmannG. and DalalK.: ‘Development and present situation of low alloyed PM steels using MCM and MVM master alloys’, Powder Metall. Int., 1979, 11, 177–180.
3.
SchlieperG. and ThummlerF.: ‘High strength heat-treatable sintered steels containing manganese, chromium, vanadium and molybdenum’, Powder Metall. Int., 1979, 11, (4), 172–176.
4.
BanerjeeS., GemenetzisV. and ThümmlerF.: ‘Liquid phase formation during sintering of low-alloy steels with carbide-base master alloy additions’, Powder Metall., 1980, 23, (3), 126–129. doi: 10.1179/pom.1980.23.3.126
5.
BanerjeeS., SchlieperG., ThümmlerF. and ZapfG.: ‘New results in the master alloy concept for high strength sintered steels’, Prog. Powder Metall., 1980, 13, 143–157.
6.
FischmeisterH. and DrarH.: ‘Zinc as an alloying element in Cu–Mn–steel powder forgings produced by liquid–solid alloying’, Powder Metall. Int., 1977, 9, (3), 114–118.
7.
FischmeisterH. F. and LarssonL. E.: ‘Fast diffusion alloying for powder forging using a liquid-phase’, Powder Metall., 1974, 17, (33), 227–240. doi: 10.1179/pom.1974.17.33.015
8.
ChenM.-H.: ‘Liquid phase sintering of iron with copper base alloy powders’; 2010, Lawrence Berkeley National Laboratory, LBNL, Berkeley, California, US. Paper LBL-5770. Retrieved from: http://escholarship.org/uc/item/20v4v8kk.
9.
MocarskiS.: ‘Method of making sintered powder alloy compacts’, Patent US 4382818 A, U.S., 10 May, 1983.
10.
MocarskiS.: ‘Master alloy for powders’, Patent US 4071354 A, U.S., 31 Jan, 1978.
11.
MocarskiS., ChernenkoffR., McHughC. O., YeagerD. A., ChenernkoffR. A. and ChernenkoffR. A.: ‘Liquid phase sintered powder metal articles’, Patent US 5872322 A, U.S., 16 Feb, 1999.
12.
MocarskiS., HallD. W., ChernenkoffR. A., YeagerD. A. and McHughC. O.: ‘Master alloys to obtain premixed hardenable powder metallurgy steels’, Powder Metall., 1996, 39, (2), 130–137. doi: 10.1179/pom.1996.39.2.130
13.
Gomez-AceboT., SarasolaM. and CastroF.: ‘Systematic search of low melting point alloys in the Fe–Cr–Mn–Mo–C system’, Calphad, 2003, 27, (3), 325–334. doi: 10.1016/j.calphad.2003.12.001
14.
CastroF., SarasolaM., SainzS. and Gómez-AceboT.: ‘Processing routes for obtaining novel high performance Mn-containing PM steels’, Mater. Sci. Forum, 2007, 534–536, 705–708. doi: 10.4028/www.scientific.net/MSF.534-536.705
15.
SarasolaM., SainzS. and CastroF.: ‘Liquid phase sintering of PM steels through boron-containing master alloy additions’, EuroPM 2005, Prague, Czech Republic, 2–5 October, 2005, EPMA, 349–356.
16.
OroR., BernardoE., CamposM. and TorralbaJ. M.: ‘Liquid phase sintering control based on effective alloying design’, EuroPM 2012, Basel, Switzerland, 16–19 September, 2012, EPMA.
17.
BernardoE., de OroR., CamposM. and Manuel TorralbaJ.: ‘Design of low-melting point compositions suitable for transient liquid phase sintering of pm steels based on a thermodynamic and kinetic study’, Metall. Mater. Trans. A, 2014, 45, (4), 1748–1760. doi: 10.1007/s11661-013-2137-5
18.
OroR., CamposM. and TorralbaJ. M.: ‘Study of high temperature wetting and infiltration for optimising liquid phase sintering in low alloy steels’, Powder Metall., 2012, 55, (3), 180–190. doi: 10.1179/1743290111Y.0000000007
19.
OroR., CamposM., TorralbaJ. M. and CapdevilaC.: ‘Lean alloys in PM: from design to sintering performance’, Powder Metall., 2012, 55, (4), 294–301. doi: 10.1179/1743290112Y.0000000016
20.
GermanR. M.: ‘Chapter Nine – Sintering with a liquid phase’ in ‘Sintering: From empirical observations to scientific principles’, (ed. GermanR. M.), 247–303; 2014, Boston, Butterworth-Heinemann.
21.
DezellusO. and EustathopoulosN.: ‘Fundamental issues of reactive wetting by liquid metals’, J. Mater. Sci., 2010, 45, (16), 4256–4264. doi: 10.1007/s10853-009-4128-x
22.
EustathopoulusN., NicolasM. G. and DrevetB.: ‘Chapter 5 Wetting properties of metal/metal systems’ in ‘Wettability at high temperatures’, 175–197; 1999, Oxford, UK, Pergamon Materials Series, Elsevier Science Ltd.
23.
YinL., ChauhanA. and SinglerT. J.: ‘Reactive wetting in metal/metal systems: dissolutive versus compound-forming systems’, Mater. Sci. Eng. A, 2008, 495, (1–2), 80–89. doi: 10.1016/j.msea.2007.11.097
24.
DanningerH. and GierlC.: ‘Processes in PM steel compacts during the initial stages of sintering’, Mater. Chem. Phys., 2001, 67, (1–3), 49–55. doi: 10.1016/S0254-0584(00)00419-3
25.
DanningerH. and GierlC.: ‘New alloying systems for ferrous powder metallurgy precision parts’, Sci. Sintering, 2008, 40, (1), 33–46. doi: 10.2298/SOS0801033D
26.
OroR., CamposM., Gierl-MayerC., DanningerH. and TorralbaJ.: ‘New alloying systems for sintered steels: critical aspects of sintering behavior’, Metall. Mater. Trans. A., 2015, 46, (3), 1349–1359. doi: 10.1007/s11661-014-2707-1
27.
RangaswamyS. and FortunaD.: ‘Iron-based braze filler metal for high-temperature applications’, Patent US 20080006676 A1, U.S., 10 Jan, 2008.
28.
SokolowskiP. K., MurphyT. F. and LindsleyB. A.: ‘Considerations in sinter-brazing PM components:’ 2010Powder Metal World Congress & Exhibition, Florida, 27–30 June, 2010, 2010, Metal Powder Industries Federation (MPIF), Edited in CD, ISBN:9780981949642, 0981949649.
29.
DanningerH.: ‘Sintering of Mo alloyed P/M structural-steels’, Powder Metall. Int., 1988, 20, (4), 7–11.
30.
BernerD., ExnerE. and PetzovG.: ‘Swelling of iron-copper mixtures during sintering and infiltration’, Mod. Dev. Powder Metall., 1974, 6, (237).
31.
DautzenbergN. and DorweilerH. J.: ‘Dimensional behavior of copper–carbon sintered steels’, Powder Metall. Int., 1985, 17, (6), 279–282.
