MECHANICAL BEHAVIOUR OF POWDER METALLURGICAL MATERIALS

Abstract

Different powder metallurgy (P /NI) production techniques for some wiclly used metal componds, primarily to t.akc advantage of possibility l.o produce technical pa.rts with near net shape technique inst<•.'acl of t.lw usual w;ty of cast.ing usually followed by expensive machining to achiew the desired geotnetry of the work piece. The selection of investigated P /M alloys :31GL, Udimct-700 and Stellite alloy No.6, were

chosen because of wick spectrum of their technical application and because of the fact

- with some exceptions - ilJal. they arc up to now, uonnil.lly not produce parts by the powder met.allurgiud route. The maHufacturiHg of tl1c pilrts iln.' pcrforn1cd by : I) Met.ill Injection Moulding {MIM)­ debinding- sintcring. In this n1ct.hod (MIM), the powder is first hiudccl into a solid "green body" then extruded similarly to t.lw polymers. 2) Wet. Powder Pouring {WPP)- debin­ ding and sintcring in one process . In both cases ultimate densification to solid density is performed by subsequent" II!Ping" of the siutcred bodies. The new nwi.hodology {WPP) of mixing the powder with tlw binder anclliqnid snspcnsion have been poured on a rubber mold without appling prcssnre. Tl1e process has been carried ont at room temperature. The new technique has been developed as a fast and economic nearest net shape forming. 3) Hot Isostatic Pressing (HIP), only, IIIPing of the powder alloy poured into an adequate formed capsule, which is then cvaci\ated bdore scaling. Widely optimised "prograrns" for dchinding and sintering have been performed to achieve

95 % of the solid desity of the <•.>ud pmducts. The subsequent containerless "HI Ping" of part a.lloy have a.tl.ributed due to the 95 %of the solid density. The samples of the clifl'crent alloys are produced in di[[',,rtcut ways:

1) In the case of :316L steel samples ilre prepared via Mll'vl-sintering and HIPing a.nd compared with samples prepared by HIP and by conventiona.l metal forming processes as hot rolling. Three different time functions for l1cil.l.ing during the HIP process and six different hea.t treatments were applied to optirnize the properties. High temperature creep tests were carried out on tl1e P /I'd material with the difrcreut production and treatment c01ldition. In addition a cornincrci;,l l(()t-rolled tn;licrial was heal. treated and tested.