New High Performance, LowAlloy Steel Powder from

HoeganaesA new high compressibility wateratomiz ed metal powd er which con ­tains Mo as its primary alloying ele­mentand which responds well to heattreatment to provide high tensil eimpact and fatigue properties, waslaun ched at the 1990 PM Conference& Exhibit ion held in Pittsburgh inMay. According to William H.Michael, vice- president of sales andmarketing at Hoeganaes Corp., thenew steel powd er - designatedAncorstcol 85 HP (0.84MoO.14Mn-

. 0.01C-0.07 O2 - can be compacted todensities much higher than the cur­rent prealloyed nickel-molybdenum4600-grade powd ers. For exampl e,green density of 6.8 g/cm3 can beachieved at a compactin g pressure of30 tsi, 7.0 g/cm? at 40 tsi,and in excessof 7.2 g/cm? at 50 tsi.Research work done at Hoeganaes'metal powder plant in Riverton, NewJersey. has shown that sintered

powder over the past two and a halfyears was to extend PM part perfor­mance close to that of their wroughtcounterparts, particularly for highstrength compon ents now demand edfor applications such as aut omotivetrans mission and engine compo­nents.Michael also stated that the powderwas ideally suited for double press/double sintering operations (OP/OS)where densities of up to 7.4/7.5 g/crn!are attainable. In tests done to eva­luate the properties of OPIDSAncorst eel 85HP, compacts pressedat 45 tsi were presintered at ca. HOOF.repressed at 45 tsi and sintered at2050F for 30 min. in dissociatedammonia to final densities of 7.51 g/em". Addit ional heat treatment [aus­teniti zing at 1650F for 30 min. in dis­sociated ammonia follow ed · byquenching in oil prehea ted to 150F,and tempering for 60 min. in argon to

William H Micha el presented details ofHoeganaes' ne whigh-performance 101V alloy steel powder at Pittsburgh

FIG. 1 Photomicrograph ofAncorsteel85 HP mixed with 0.2% graph itein the as-sintered condition. The structure is made up of two consti­tuents;polygonal ferritegrains and an aggregate ofaccicular f errite andcarbide (dark etching). The etchant was 2% nital, 4% picral (frompaper by Fulmer and Causton. presented 1990PMConference. Pittsburgh)

FIG.2 Photomicrograph ofAncorsteel85 HPmixed with 0.4% graphitein the as-sintered condition. Th e structure is a uniform aggregate ofacdcular ferrite and carbide. Th e etchant was 2% nital, 4% picral(from paper by Fulm er and Causton, presented 1990 PM Conference,Pittsburgh)

FIG. 3 Fatigue performance and tensile strength of Ancorsteel 85 HP

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Ancorsteel 85HP containing 0.2%graphite has a mixed structure ofpolygonal ferrite [Fig.I ] and a darkeretching constituent that is an aggre­gate of accicular ferrite and carbides.At graph ite addit ions above 0.4% themicrostructure is an uniform aggre­gate of accicular ferrite and carbidethrough out (Fig.2). The companystated that it is thi s uniform microst­ructure which produces consistentmechanical prop erties and dimen­sional change char acteristics over therange ofgraphite additions from 0.4 to0.8%.Michael stated that the new wateratomized prealloyed powder is themost versatile low alloy steel powd eron the market in North America. andclaimed that it sur passed any otherlow alloy steel powder both in per­formance and economics. He said thatthe objective in developing this new

prevent decarburi zation) of the OP/OS compacts showed a tensile andfatigue strength of 182,671 and 63.336psi respectively, which compares fav­ourably with high temperature sin­tered DPIDSPM low alloy steel basedon 4600V powder fFig.3).In add ition to offering similar perfor­mance to existing nickel steel alloys.the Mo-alloy steel powder also avoidsthe price instability that is associatedwith the nickel market. It was statedthat the price of the new powder islower than both Hoeganaes Ancors­teel4600V and Ancorsleel 2000, bothprealloyed nickel steel powd ers.Michael also believed that the newpowd er would form the basis for thedevelopment of other new high per­formance steel s, particularly forcomponents requi ring high densityand hardenability.

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MPR July/August 1990 565