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ID:36596551
大小:11.66 MB
页数:133页
时间:2019-05-12
《WCCo复合粉的原位合成与块体硬质合金的烧结》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、北京工业大学博士学位论文WC-Co复合粉的原位合成与块体硬质合金的烧结姓名:刘文彬申请学位级别:博士专业:材料科学与工程指导教师:张久兴;宋晓艳20090301北京工业大学工学博士学位论文体材料。全面研究了SPS各工艺参数对烧结硬质合金块体显微组织和性能的影响。实验结果表明,超细复合粉的致密化开始于8040C,于11750C固相致密化结束:烧结温度、烧结压力和保温时间明显影响WC平均晶粒尺寸及尺寸分布进而影响力学性能。在优化工艺参数一烧结温度13250C、烧结压力50MPa、保温6.8min的条件下,获得W
2、C.6Co硬质合金块体材料的优良综合性能:硬度92.6HRA、断裂韧性12MPa·m¨2、横向断裂强度为2180MPa。探讨了复合粉中添加晶粒生长抑制剂对烧结块体WC晶粒尺寸和硬度、韧性的影响,并讨论了硬质合金块体材料的断裂机制。关键词WC.Co复合粉:原位反应合成:反应热力学;放电等离子烧结:力学性能ABSTRACTABSTRACTComparedtomicro·-grainedalloy,ultrafine·-grainedandnanocrystallinecementedcarbideshavemu
3、chhigherhardness,wearresistant,fracturetoughnessandtransverserupturestrength.Therefore,theresearchontheultrafine—grainedandnanocrystallineWC·Cocementedcarbidesbecomesanimportantdevelopingdirectioninthehardmetalindustry.ThesynthesisofWC—Copowderanditssinter
4、ingaretwokeystepsinpreparingtheultrafinestructuredcememedcarbides.Firstly,takingadvantageofsparkplasmasintering(SPS)technique,weinvestigatedtherapidrouteforsynthesisofWC-6wt.%Cocompositepowderbyinsitureductionandcarbonizationreactionsandimmediateconsolidat
5、ingthecompositepowderintothebulkinSPSsystem,usinglow—costtungstenoxide,cobaltoxideandcarbonblackasrawmaterials.Thewholeprocesswimthedurationlessthan30mincouldbedividedintofourstages,i.e.,theheatingofthepowdermixture,insitureductionandcarbonizationreactions
6、,sinteringdensificationandisothermalholding。Theeffectsofmillingtimeontheparticlesizeandsizedistribution,andtheeffectsoftheamountofcarbonadditioninthemixturepowders,thereactiontemperature,thesinteringtemperature,theholdingtimeandthesinteringpressureonthepha
7、sesandpropertiesoftheas-sinteredbulk,wereanalyzedsystematically.Thecementedcarbidesbulkswithhighdensityandgoodcombinedmechanicalproperties、Ⅳereobtained.ThemechanismoftherapidinsitupreparationofcementedcarbidesbulksintheSPSsystemWasproposedforthefrsttime.Ac
8、cordingtOthephenomenonofmeltingorboilingatthesinteringneckandthethermodynamicsofreactions,thereasonsoftheincreasedrateinthenon-equilibriumreactionsandthedifferencesofthereactionamountandthetypeandamountofther
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