| Sintering of iron-based powder metallurgy parts products is high-yield andapplication far and widely in the powder metallurgy technology. In recent year,these powder metallurgy parts products are in great request in properties. On theone hand, so study and research of the high-powered iron-based powder metallurgyparts is extraordinary important. On the other hand, it is little report on thecarbusintering of the powder metallurgy compacts, especially, the process of thecarbusintering of the powder metallurgy compacts and the important effectparameters on the carbusintering. The compacts density requests fartherimprovement.Taking account to the raw material source, the economical benefit and thetechnique conditions, we study the preparation technology and the theory researchof high properties iron-based powder metallurgy parts;otherwise, it has the practiceapplication and theory worthiness to research the technology of surface-hardentreatment of powder metallurgy parts.The present paper mostly researches the process of carbusintering technique.Against such a background, this paper was firstly aimed at the current processingroute of the carbusintering for textual research, and then presented a novel andmore feasible approach of solid carbusintering techniques attribute of Fe-Ni,Fe-Ni-Cu–Mo and Fe-Ni-Cu-Cr-Mo material system and feature of thecarbusintering technique, followed with a deep and systematic study to test andrealized it. A basic frame of carbusintering of Fe-Ni typical powder material systemhas been established. The effects treatments on the microstructure had beeninvestigated by means of SEM,OLYMPUS,XRD etc. and the mechanicalproperties are tested by HR-150A sclerometer and MM-200 wear test. The carbonconcentration is maturated by LGP-C/S analyzer.By adjusting carbusintering parameters, the samples treated zone was observedand the properties of carbusintering treated specimens were examined. However wedeeply research the diffusion mechanism of carbusintering during the process. Wehave made several conclusions through theoretical and experimental investigation:(1) The microstructures are constituted of samdwich pearlite, reticulatecementite,pores and carbon in the outside of the carbusintered samples;the microstructuresobtain hypoeutectoid in the center of the carbusintered samples. Themicrostructures are constituted of acicular martensite, remains austenite and fewpores in the outside of the carbusintered samples after quench treatment;and themicrostructures are constituted of lathy martensite, remains austenite and few poresin the center of the carbusintered samples after quench treatment.(2) The carbusintered parts can obtain the refined structures and favorableproperties by proper re-pressed and re-sintering processes. The density is increasedfrom 6.9 g/cm3 to 7.3g/cm3 of the samples after re-pressed and re-sintering. Theappropriate quench temperature is 800℃, and surface hardness can obtain aboveHRC55, the center hardness is about HRC40.(3) For sintering steel, the alloy element Cu is contributed to improve theproperties of the iron-based materials. The 1.5% Cu content is appropriate, thehardness can obtain HRC65. But the alloy element Cu tends to carbides withcarbon atom, so the cementite of the pearlite is alloy cementite. The 1.5-2.0% Crcontent is appropriate;the hardness can obtain about HRC55.(4) The depth of carbusitering is increased with carbusintering time. Therelationship of them is δ2=k.τ function. By experiment data, it can obtaink=0.80~0.81 in 1100℃, k=0.95~0.96 in 1150℃ and k=1.49~1.50 in 1180℃ aftercarbusintering.(5) The carbusintered mechanism accords with Fick' second law, and thediffusing coefficient is temperature and carbon concentration function. Carbonconcentration accords with exponential degressive orderliness. The non-linerregress equation is( ) ( ) Wc =A0 +B1exp ?x/t1+B2exp?x/t2.(6) According to classical diffusion theory, we can obtain that the diffusioncoefficient is D0 =1.515×10-2cm2/s, the diffusion active energy isQ=183.74×103J/mol and the carbon potential is 1.87wt% by steel-sheet method,and the transfer coefficient is β =5.55 ×10-4 cm/s.(7) The solid carbusintered specimens have considerably lower 17% frictioncoefficient compared to conventional sintered specimens, almost all the specimenswith heat treatment have lower friction coefficient compared with these withoutheat treatment. The worn debris was characterized by dark brownish-red color,therefore, it is deduced that oxidation-determined wear may be predominantmechanism for the given testing conditions.In a whole, based on the systematic study of the above three typical powdermaterial systems, a basic frame of solid carbusintering of powder compacts hadbeen established. It is considered that some work in this paper is not only for theimprovement on the current carburization technology, but also the importantsupplement of the conventional solid carburization technology mode and itstheories. Also, it provides a referable processing route and ideology for the currentresearch of solid carburization technology. Therefore, the work in this paper is ofgreat and profound values in theory and practical application.
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