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Effect of elements on performance of alloys in arsenic based conditions

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Heanjia Alloys
Heanjia Alloys

Nickel based alloys such as Hastelloy X and Inconel 617 are evaluated for their performance in atomic energy sector

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Effect of elements on performance of alloys in Arsenic based conditions Nickel isthe mainconstituentinthe initial subscale.Thisisfeaturedtothe higherreactivityof nickel witharseniccomparedwithother elements likechromiumandiron.Forthisreasonnickel quickly reactedwitharsenicinpreference toothercompositionalelements.NiAscancreate several forms basedon ASto Ni ratio.Nickel arsenidiesattemperature of 650oCor 700oC can be noticedas four intermetalliccompounds.Itisanticipatedthatmostarsenicricharsenidesdevelopedinitiallynextto gas-alloysurface interface andthe mostarsenicdeficientarsenidiesnexttothe alloysurface.Due to highdiffusivityof arsenicgasinalloythe nickel arsenideschange fromone phase toanother beginningfromthe surface incontactwithgas environmentandtenthroughthe developedscale and coldalsobe foundtogetherinthe scale.The lattice defectsconcentrationisanticipatedtobe highfromthe beginningof corrosionprocessbecause of the continuouschangingof NiAssystem fromone phase to anotherbasedon the abundance of Arsenicinthe layer.NotjustNiAshave more than one phase howeveralsothe otherelements. Chromiumeffect It was evidentfromthe outcomesthatchromiumdidnotproduce asecuritylayerasthat in the othersystem.Chromiumisalowerreactive elementwithrespecttonickel andarsenic.Thus, chromiumremainedunreactive toarsenictill itsconcentrationreachedaspecific value inalloyside of the arsenic-alloymatrix interface,thenitbegantoproduce Cr arsenides.Thisphenomenacould alsobe explainedasthissubscale mayhave lardervoidsormicrochannelsconcentrationthanthe otherswhichmaybe filledwitharsenic vaporresultinginincreasingthe arsenicvaporpressure in thissubscale thanthe precedingone.Increase invaporpressure resultsindepletingthe lessreactive elementwhilethe higherreactivityelementshadalreadyreactedfromthe normal diffusive arsenic. Effectof iron For HastelloyXandInconel 600 samples,whichcomprisedironasa constituentelementof alloys,it was noticedthatreducingthe nickel concentrationwasaccompaniedbyincreasingthe iron concentrationandvice versa.
Effectof cobalt Howevercobaltismore reactive toarsenicthan ironand itwas anticipatedthatcobaltwasnot foundinthe scale for HastelloyX.Thismightbe due to low concentrationof cobaltinthisalloy, althoughforInconel 617 whichcontainscobaltin12.5% wasfoundinthe scale. Effectof temperature Increasingthe testtemperature from650oC to 700oC, resultedinincreasingthe corrosion susceptibilityandhence metal loss.Thisisbecause arsenicvaporpressure isextremelysensitiveto temperature.Whentemperature is650oC,the vapor pressure is2 bar but whentemperature is increasedto700oC, the pressure reaches5bar. Increase invapor pressure causesincreasedreaction rate andhence corrosionrate. Heanjiaproduceshighstrengthnickel basedsuperalloyswhichare designedforservinginthese challengingapplications.Thesealloysare producedindifferentformsandspecifications,socontact us todayto discussyourrequirement.

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Effect of elements on performance of alloys in arsenic based conditions

  • 1. Effect of elements on performance of alloys in Arsenic based conditions Nickel isthe mainconstituentinthe initial subscale.Thisisfeaturedtothe higherreactivityof nickel witharseniccomparedwithother elements likechromiumandiron.Forthisreasonnickel quickly reactedwitharsenicinpreference toothercompositionalelements.NiAscancreate several forms basedon ASto Ni ratio.Nickel arsenidiesattemperature of 650oCor 700oC can be noticedas four intermetalliccompounds.Itisanticipatedthatmostarsenicricharsenidesdevelopedinitiallynextto gas-alloysurface interface andthe mostarsenicdeficientarsenidiesnexttothe alloysurface.Due to highdiffusivityof arsenicgasinalloythe nickel arsenideschange fromone phase toanother beginningfromthe surface incontactwithgas environmentandtenthroughthe developedscale and coldalsobe foundtogetherinthe scale.The lattice defectsconcentrationisanticipatedtobe highfromthe beginningof corrosionprocessbecause of the continuouschangingof NiAssystem fromone phase to anotherbasedon the abundance of Arsenicinthe layer.NotjustNiAshave more than one phase howeveralsothe otherelements. Chromiumeffect It was evidentfromthe outcomesthatchromiumdidnotproduce asecuritylayerasthat in the othersystem.Chromiumisalowerreactive elementwithrespecttonickel andarsenic.Thus, chromiumremainedunreactive toarsenictill itsconcentrationreachedaspecific value inalloyside of the arsenic-alloymatrix interface,thenitbegantoproduce Cr arsenides.Thisphenomenacould alsobe explainedasthissubscale mayhave lardervoidsormicrochannelsconcentrationthanthe otherswhichmaybe filledwitharsenic vaporresultinginincreasingthe arsenicvaporpressure in thissubscale thanthe precedingone.Increase invaporpressure resultsindepletingthe lessreactive elementwhilethe higherreactivityelementshadalreadyreactedfromthe normal diffusive arsenic. Effectof iron For HastelloyXandInconel 600 samples,whichcomprisedironasa constituentelementof alloys,it was noticedthatreducingthe nickel concentrationwasaccompaniedbyincreasingthe iron concentrationandvice versa.
  • 2. Effectof cobalt Howevercobaltismore reactive toarsenicthan ironand itwas anticipatedthatcobaltwasnot foundinthe scale for HastelloyX.Thismightbe due to low concentrationof cobaltinthisalloy, althoughforInconel 617 whichcontainscobaltin12.5% wasfoundinthe scale. Effectof temperature Increasingthe testtemperature from650oC to 700oC, resultedinincreasingthe corrosion susceptibilityandhence metal loss.Thisisbecause arsenicvaporpressure isextremelysensitiveto temperature.Whentemperature is650oC,the vapor pressure is2 bar but whentemperature is increasedto700oC, the pressure reaches5bar. Increase invapor pressure causesincreasedreaction rate andhence corrosionrate. Heanjiaproduceshighstrengthnickel basedsuperalloyswhichare designedforservinginthese challengingapplications.Thesealloysare producedindifferentformsandspecifications,socontact us todayto discussyourrequirement.