Mechanical and corrosion properties of sintered duplex stainless steels

Mechanical and corrosion properties of sintered duplex stainless steels

M.Youseffi, K.O.Loke. (University of Yorkhire, Bradford, (Quebec Metal Powders Ltd, It was reported that 304L stainless steel parts had been made...

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M.Youseffi, K.O.Loke. (University of Yorkhire,

Bradford,

(Quebec

Metal

Powders Ltd,

It was reported that 304L stainless steel parts had been made at injection pressures below 1 MP?, using a complex polyolefin-liquid paraffin binder. Solvent (water or ethanol) and thermal debinding were used with good shape retention. Sintering attained density of near 8.0 g.cmd3, and tensile strength of 600 MPa with 45% elongation. Feedstock solids loading of 62.5% was mouldable but there was barrel seizure at 65% solids. The method was shown to allow less equipment wear, less anisotropy in parts and reduced costs.

It was noted that steels made from diffusion bonded powders exhibit good dynamic properties. This was attributed to Ni-rich zones, retained austenite and the type of martensite, which depend on process conditions. The effects of sintering temperature, 1120 or 1250 “C, 0.5 to l.O%C and other process conditions, on diffusion of Ni in diffusion bonded Fe4.O%Ni-1.5%Cu-0.5%Mo were investigated. Samples were characterized by microscopy and electron probe microanalysis to determine the proportions of micro-constituents.

Effects of particle size distribution and binder characteristics on feedstock flow

Binder treated analogues of diffusion alloyed steels

R.M.Germatlet al. (Penn State University,USA.) The effects of powder particle size distribution and binder characteristics on feedstock viscosity were discussed. Flow was shown to depend on inter-particle separation and rheological properties of the binder. The role of particle size distribution on interparticle distance and the role in prediction of flow properties were presented. Effects of particle orientation close to tool walls and lubricating effects of binder were considered. A two-dimensional model, to aid in understanding flow of suspensions, was described.

Injection moulding of microparts C.Kukla.

(Battenfeld

Injection

M&ding

Technology,

AL6ti.)

The trend to miniaturization of parts was noted and use of powder injection moulding to make small components was discussed. It was reported that servo-electric-micro-moulding machines were available for manufacture of small parts.

Simulation of injection moulding effects of thermal and inertial effects on flow stability J.F.Heru et al. (NationalResearchCouncil,Canada.) It was reported that a three-dimensional transient finite element method had been used to optimize MIM. Inertial effects and free surfaces were considered. Flow of 17-4 stainless steel powder with a water-soluble binder, used to make thick parts through a diaphragm gate, was simulated to identify thermal and flow conditions giving rise to symmetric and asymmetric flow. The simulation predicted observed non-uniform unstable flow and provided guidance in achieving stable operation.

Diffusion alloys _ Effects of sintering temperature

carbon content and heat treatment on properties of steel

40

L.Tremblay, EChagnon. Cal&l.)

UK.)

MPR June 2001

et al.

Effects of sintering conditions and heat treatment on steel from diffusion bonded powders G.Silva

et al. (Polytechnic

ofMilan, Italy.)

A study of the effects of sintering conditions on structure and properties of diffusion bonded Fe-1.75%Ni-1.5%Cu-0.5%Mo-0.2%C was described. Sintering was either at 1120 “C for 30 min in endo-gas for one or more times or once at 1250 “C for 1 h in N-H-CH,. Sintering once at 1250 “C gave similar results to sintering several times at 1120 “C. Materials did not homogenize even after prolonged sintering.

High density steels Hardenability of sintered boroncarbon steels R.J.Caurton et al. (HoeganaesCarp, USA.) The effect of less than O.O9%B on hardenability of Fe-B-0.3%C steels was investigated. Jominy test bars were cold isostatically pressed and sintered at 1120 or 1230 “C in dry H. It was shown that B enhances hardenability and hardness particularly on sintering at 1230 “C.

High density high strength [email protected] steel matrix composites R.R.PhiUips.(EngineeredPressedMammals,USA.) Production of a Ni-Mn-Mo steel matrix composite was described. Samples were pressed at 420 or 640 MPa and sintered using a commercial cycle. The composite was formed in situ during sintering. Structures and properties were described. Properties could be enhanced by heat treatment to promote secondary hardening.

High density PM steel N.S.Myers, University,

R.M.Germn. USA.)

(Pennsylvania

Stainless steels

.

Corrosion of austenitic stainless steels containing boron

(HoeganaesCarp, USA.) The mechanical properties of rwo steels, made from diffusion bonded powder with Cu added or with 2%Cu and 4%Ni were described. R.J.Cau.stm

It was noted that a challenge to the PM industry is to produce steels with densities exceeding 7.2 g.cms3 by a single-press/singlesinter route. Methods not allowing open porosity, such as casting and forging, were mentioned. A study incorporating new and existing technology to attain near full density in Ni-Mo steels, with minimum distortion was reported. The investigation concentrated on elimination of final porosity, heat treatment response, optimization of properties and reproducibility.

State

P.K.Samal,J.B.TeweIl. (OMG Americas, USA.) It was noted that a small amount of B enhances sintering, strength and ductility of stainless steels. The paper reported studies of the effect of B on corrosion resistance of a range of stainless steels in 5%NaCl solution. Comparison was made with stainless steels densified by impregnation with resin.

Effect of structure and pore morphology on strength and creep of PM stainless steels et al. (Pennsylua$a State Uniuersiry, USA.) Properties of PM alloys were discussed with reference to structure and pore characteristics. Studies of the effects of structure, porosity and related sintering parameters on mechanical and corrosion properties were described. It was established that there are relationships between fatigue properties and porosity and between creep properties and density. There were wide variations in creep rupture times, which were attributed to statistical distributions of pores. B.A.Shaw

Mechanical and corrosion properties of sintered duplex stainless steels A.Molimti

et al (University

ofTrento,

Trento, Italy.)

Properties of duplex stainless steels were discussed. An investigation of mechanical and corrosion properties of these stainless steels, made from water atomized austenitic 316L and ferritic 434L powders, was described. Properties were correlated with structures. Large differences between the duplex steels and the ferritic and austenitic steels were found.

Copper and copper alloys Properties of copper-silver and dispersion strengthened copper H.E.Kelley

et al. (American C&met,

USA.)

The need for materials with high strength and thermal conductivity at elevated temperatures was discussed with regard to the use of Cu-Ag and dispersion strengthened Cu. Properties of sintered alloys were studied at

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