Pressing vacuum sintering of multipowders for manufacturing novel engine valve seat on Gleeble 1500 simulator

Patented Fe based multipowders for manufacturing novel engine valve seat were compacted and sintered using a Gleeble 1500 thermal simulator system. Microstructures and properties of the sintered alloy have been studied by hardness test, optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) analysis. Results indicate that a sintered alloy with a hardness of 38 HRC and a density of 7·23 g cm⁻³ can be obtained when the green compacts are sintered at 1240°C for 30 min. It is found that lattice parameters of the alloy matrix increase with increasing sintering temperature. Additionally, the investigation of green compacts’ shrinkage during sintering shows that there is a threshold value for the density of the green compacts. When the density of the green compacts is lower than that value, the density of the sintered alloy remains almost constant with increasing density of green compacts. An equation to calculate the threshold density has been suggested as νρ² = C ₁ ρ² + C ₂ m² + C ₃ m ρ.