The Properties of Fe-Ni-Mo-Cu-B Materials Produced Via Liquid Phase Sintering

Abstract

Sintered materials base on pre-alloyed powders (Fe-Ni-Mo-Cu) are expansively applied in the automotive industry. However, their applications are limited by the particular porosity values of those materials. To reduce the porosity and, simultaneously, to increase the consolidation of sintered alloys, miscellaneous methods within powder metallurgy technologies are utilised, as well as an activated sintering process; for example some boron is added. The boron and iron built a system that is not soluble in any of the three allotropic forms of iron. While sintering at a temperature higher than 1433 K, a permanent liquid phase was generated as a result of a eutectic reaction between iron and Fe 2 B. Owing to the limited boron solubility in iron, a liquid phase was continuously present during the sintering process, influence changes in the morphology of the porosity and the increase in density, also mechanical properties. In addition, boron showed a strong chemical affinity to oxygen; in sintering process it reacted with a chemically bound oxygen on the surface of powder particles and it simultaneously activated the sintering process. The paper presents the production of sintered materials based on Höganäs Distaloy SA (Fe-1.75% Ni-0.5% Mo-1.5% Cu) powder modified by boron powder in amounts of 0%, 0.2%, 0.4% and 0.6%. Alloys were manufactured using powder metallurgy technology through mixing of powders, compacting at 600 MPa pressure and sintering at 1473 K, during 30 minutes in hydrogen atmosphere. One of the phenomenon, which exists on the surface of sinters made from boron modified pre-alloyed powders (Fe-Ni-Mo-Cu) type Distaloy SA is creating a thickened layer. The similar thickened layer was observed also on the surface of another samples base on pre-alloyed powders with boron addition.As well as the properties: density, hardness, tensile strength were examined and microstructure investigations were performed. Experimental results showed that if boron was added, while sintering, the shrinkage phenomena increased and properties were improved.Keywords: pre-alloyed powders, boron, activated sintering, thickened layer, properties, microstructure Materiały spiekane na osnowie stopowanego proszku Fe-Ni-Mo-Cu znajdują szerokie zastosowanie w przemyśle motoryzacyjnym. Jednakże ze względu na pewien stopień porowatości tych materiałów ich wykorzystanie jest ograniczone. Ażeby obniżyć porowatość i równocześnie podwyższyć zagęszczenie stopów spiekanych stosuje się różne warianty technologii metalurgii proszków oraz procesy aktywowanego spiekania, na przykład poprzez wprowadzenie dodatku boru. Bor tworzy z żelazem układ o prawie całkowitym braku rozpuszczalności w obu odmianach alotropowych Przy spiekaniu powyżej 1143 K w wyniku reakcji eutektycznej pomiędzy żelazem a Fe 2 B tworzy się faza ciekła. Wskutek ograniczonej rozpuszczalności boru w żelazie proces spiekania przebiega przy ciągłej obecności fazy ciekłej, co w konsekwencji wpływa na zmiany w morfologii porowatości , wzrost zagęszczenia i podwyższenie właściwości mechani...

Elastic Properties and Structural Observations of Distaloy Sa Powder Sintered With Boron and Carbon

“…It was found that, in the activated sintering process, the following compounds are formed in the Distaloy SA with 0.6 wt.% B specimen: Fe 2 B, FeMo 2 B 2 , and NiB; while, in the sample made of Distaloy SA with C and B -Fe 2 B, NiB, and Mo 2 B are present. As mentioned in [6,[11][12][13][14][15], the effective role of the borides is to decrease the sintering temperature and increase the amount of liquid phase. It is also to note that, in the samples containing carbon, cementite Fe 3 C is formed.…”

Effect of molybdenum addition on the mechanical properties of sinter-forged Fe–Cu–C alloys

“…for the improvement of specific properties like strength, hardness, toughness, frictional and anti-frictional properties, wear resistance, fatigue, etc. [18][19][20][21][22][23][24][25][26][27][28].…”

In Situ Formation of TiB2 in Fe-B System with Titanium Addition and Its Influence on Phase Composition, Sintering Process and Mechanical Properties

“…There is, however, no agreement between these 158 results in respect to the magnitude of changes. The shrinkage observed in dilatometric samples was 159 heavily impaired by the evaporation of the boron from the sample surface[22]. Missing boron 160 resulted in creation of smaller amount of eyectic phase.…”