Effects Of Amide Lubricant And Pre-diffusion Cr On Microstructure And Properties Of Fe-based Powder Metallurgy Materials

Fe based powder metallurgy（PM）materials are the most widely used materials in the powder metallurgy industry at present,and are widely used in automobile industry.The rapid development of the automobile industry promots the rapid growth of the powder metallurgy industry,and the improvement of the performance of the automobile has put forward higher requirement for the performance of Fe based powder metallurgy materials.The existence of pores and the inhomogeneity of microstructure are two important factors that affect the mechanical properties of powder metallurgy materials.Therefore,the mechanical properties of Fe based powder metallurgy materials can be improved by reducing the porosity and improving the uniformity of microstructure.This paper selects Fe-Ni-Mo-Cu-C powder metallurgy material,the effects of EBS and erucylamide composite lubricant with fine graphite powder on the properties of Fe based powder and green compact and the effects of pre-diffusion temperature and pre-diffusion time on the microstructure and properties of Cr contained Fe based powder metallurgy materials were investigated by SEM,EDS,XRD,powder characteristics and mechanical properties tests.Compared with the composite lubricant without fine graphite powder,the dispersibility of composite lubricant can be effectively improved with the addition of fine graphite powder,and the particle size of the lubricant becomes smaller.Compared with Fe based powder without lubricant,the green compact density of Fe based powder increases with the addition of 0.4 wt.%composite lubricant,while the flowability,apparent density and the green compact strength reduces.The flowability,the apparent density,the green compact density and the green compact strength of Fe based powder increase with the increase of amount of fine graphite powder in composite lubricant,but the effects of the amount of fine graphite powder are not obvious when it is more than 3 wt.%.The ejection force of the green compacts is reduced with the addition of the composite lubricants,the maximum ejection force dropps from 5.6 kN without lubricant to 3.9 kN with composite lubricant B₃.And the composite lubricant with the fine graphite powder distributes more uniformly on the fractures,and the particles mesh more closely.Compared with the Fe based powder without pre-diffusion,the distribution uniformity of the Cr element improves in the pre-diffused Fe based powder,and the distribution uniformity of the Cr element improves in the Fe based powder with the pre-diffusion temperature increasing.Compared with the Fe based powder sintered sample without pre-diffusion,with the pre-diffusion temperature increasing,the microstructure of the pre-diffused Fe based powder sintered specimens becomes refined and uniform,the number of fine pores and fracture dimples increases,the microhardness increases and the plastic deformation characteristics are obvious.With the pre-diffusion temperature increasing,the green density and sintered density of the pre-diffused Fe based powder metallurgy sample decrease and a large decrease appears at 840℃.The apparent hardness and bending strength increase firstly and then decreases,and the maximum value reaches at 810℃,81.4HRB and 647.3 MPa,respectively.The distribution uniformity of the Cr element improves in the pre-diffused Fe based powder with the pre-diffusion time.Compared with the Fe based powder sintered sample without pre-diffusion,the microstructure of the pre-diffused Fe based powder sintered specimens becomes refined and uniform,the number of fine pores and fracture dimples increases,the microhardness increases and the plastic deformation characteristics are obvious with the pre-diffusion time.With the prolonging of pre-diffusion time,the green density and sintered density of the pre-diffused Fe based powder metallurgy sample decrease,the apparent hardness and bending strength increase firstly and then decreases,and the maximum value reaches at pre-diffusion 40min,83.5 HRB and645.3 MPa,respectively.