Optimising grey iron powder compacts

Abstract

The grey iron microstructure Fe-2C-2Si powder based compact is tailored by different kinds of in situ and post sintering processing. This has been achieved by combining thermodynamic and kinetics modelling of microstructure development with sintering and controlled heat treatment experiments of tensile test specimens die compacted at 600 MPa. Applying optimised sintering conditions led to a grey iron like microstructure with 95% relative sintered density. Sinter hardening the compacts led to 500 MPa in yield strength and 600 MPa in ultimate tensile strength in combination with ductile fracture. Quenched and tempered condition showed the same strength values, but combined with brittle fracture due to martensitic structure. Pore rounding and partial pore filling by graphite were obtained by austenising isothermal hold during the cooling of the sintering cycle.

Graphite pore filling and surface blistering of sintered Fe–C–Si

“…The microstructure of sintered alloys containing high C and with no Si and cooled at low cooling rates may contain almost no graphite, higher amounts of pearlite and Fe 3 P if P was used as an alloying element. 11 Whereas, the alloys containing high C, Si and P result in more graphite, less pearlite and no Fe 3 P in the microstructure.…”

“…The composition of alloy 4 has been chosen from a previous study with an optimum sintering temperature of 1250uC. 3 This sintering temperature is sufficient to provide 20% liquid phase necessary to achieve the highest sinter density by taking into account C loss during the sintering cycle. In this study, however, the temperature is lowered to 1245uC to insure that no slumping occurs.…”

“…After austenitising, the components can be cooled using moderate cooling rates to obtain a pearlitic matrix or quenched in quenching media to obtain a martensitic matrix. 2,3 The main problem in the development of this approach is related to the occurrence of surface blistering in the as sintered material when sintering in N 2 atmosphere; however, blistering is not observed when sintering in vacuum. Surface blistering is related to entrapped gas pressure in the sintered material, and C deposition in the surface layer of sintered PM compacts causes significant changes in the as sintered material.…”

“…After austenitising, the components can be cooled using moderate cooling rates to obtain a pearlitic matrix or quenched in quenching media to obtain a martensitic matrix. 2,3…”

Surface and Subsurface Defects Investigation of Ni-Ti Samples Processed by Different Fabrication Methods

“…Strengthening and enhancing the properties of the composite material by alloy it with another element like iron or copper was done by Khraisat and Abu Jadayil (2010) and Khraisat et al (2009). Abu Jadayil (2010) investigated the most recent techniques of the solid object modeling.…”