Effect Of Lubricant And Process Conditions On Microstructure And Properties Of Warm Compaction Fe-based Powder Metallurgical Materials

The powder metallurgy warm compaction process is is a technology for pressing metal powder to a certain temperature to make high-density powder metallurgy parts.Lubricants and heating process are the key to warm compaction forming technology.In this paper,the microwave-heated process was used to heat warm compaction Fe-Ni-Mo-Cu-C powder metallurgy materials.The effects of Composite lubricants,Fe-based powder,Fe-based powder green compacts and Fe-based powder metallurgy sintered samples were studied by differential scanning calorimetry?DSC?,powder performance testing,green compact and sintered sample density testing,metallographic microstructure observation,scanning electron microscopy equipped with energy dispersive spectroscopy and mechanical properties testing.The main conclusions are as follows:As the content of polyamide wax increases,the glass transition temperature of the composite lubricants increases and the particle size of the lubricant decreases significantly.The flow rate and apparent density of the powder were 33-39 s/50 g and 3.196-3.257 g/cm³,respectively.The green density and bending strength of the samples compacted at 120°C increase initially and then decrease with the increase of the polyamide wax content in the composite lubricant,while the ejection force is reversed.The green density,green strength and ejection force of the A₃ sample with a polyamide wax content of 50 wt%reached 7.11 g/cm³,18.785 MPa,and 3.6 kN,respectively.In the fracture morphology of the warm-compacted samples,the number and size of the pores and the interlocking of the particles between the powders are reduced.Different from compacting samples at room temperature,the green fracture process of the warm compacted samples is more controlled by the interface between the particles and the lubricant.The sintering density of the sample added composite lubricant A₃,compacted at 120°C,was significantly improved to 7.21g/cm³,which was 0.23 g/cm³ higher than that compacted at room temperature.Compared with the Fe-based powders with polyamide wax/polyethylene wax/stearic acid amide composite lubricant A₃,the fluidity of the Fe-based powders with polyoxyethylene composite lubricant B₁ at room temperature increased to 33.4 s/50 g and the fluidity of the Fe-based powder decreased as the heating temperature increased.In microwave heating process,the heating rate of Fe-based powders with smaller mass is faster.With the mass increases,The heating rate curve shows a trend of decreasing.With the increase of compacting pressure,the green density gradually increased.At 650 Mpa compacting pressure,the green density and sintered density of the sample with polyamide wax composite lubricant at microwave heating of 120°C reached 7.21 g/cm³ and 7.417 g/cm³.The green density of Fe-based powder metallurgy sample increases first and then decreases with the increase of lubricant content and reaches the highest performance when the lubricant content is 0.6 wt.%.The properties of Fe-based powder metallurgical materials were improved by warm compaction.The hardness and bending strength of Fe-based powder metallurgical samples were improved most obviously by polyamide wax composite lubricant A₃,reaching 65 HRB and 851.8 MPa.