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.54. 北京科技大学学报 第29卷 Wear properties of reactive plasma clad(Cr,Fe)7C3/Y Fe ceramal composite coat- ings LIU Junbo),WANG Limei,HUANG Jihua2) 1)Department of Mechanical and Electronic Engineering.Weifang University.Weifang 261041,China 2)Materials Science and Engineering School.University of Science and Technology Beijing.Beijing 100083.China 3)Department of Information and Control Engineering.Weifang University,Weifang 261061,China ABSTRACT An in-situ reinforcing phase(Cr,Fe)7C3 ceramal composite coating was fabricated on the substrate of a 0.45%carbon steel using Fe-Cr C elemental powder blending by reactive plasma clad process.The mi- crostructure and micro-hardness of the coating were evaluated by SEM,XRD,EDS and micro-hardness instru- ment,the room temperature and high temperature wear properties were evaluated under dry sliding wear test conditions,and the wear mechanism was discussed.The results indicated that the reactive plasma clad ceramal composite coating has a rapidly solidified microstructure consisting of primary (Cr,Fe)7C3 and(Cr,Fe)7C3/Y Fe eutectics,with excellent wear properties under both room temperature and high temperature sliding wear test conditions. KEY WORDS ceramal composite coating;reactive plasma clad;microstructure;wear properties (上接第38页) In situ study of deformation and fracture process in wheel steel and effect of hydro- gen SHI Dongmei,LI Jinxu,DUAN Guihua),REN Xuechong,CHU Wuyang,QIAO Lijie, JIANG Bo),CHEN Gang2),CUI Yinhui2) 1)Materials Science and Engineering School.University of Science and Technology Beijing.Beijing 100083.China 2)Technology Center of Ma'anshan Steel Iron Corporation.Ma'anshan 432000.China ABSTRACI In situ tensile tests in scanning electron microscope (SEM)were carried out using single edge notched specimens of no larger than 0.5mm in thickness made of CL60 wheel steel with or without hydrogen charging.Observations under optical microscope (OM)were also done to a wedge opening loading (WOL)spec- imen with a thickness of 30mm which was precracked.The result shows that,for the thinner specimen,plastic deformation occurs firstly in proeutectoid ferrite and then grows along the prior austenite grain boundary,and then,a microcrack initiates and propagates preferentially at the interface of proeutectoid ferrite and pearlite colony.The process of deformation and fracture is almost same each other for both specimens with and without hydrogen,except that the microcrack initiates more frequently by way of inclusion separating and shelling from matrix for the specimen with hydrogen.The fracture surface fractograph of the thinner specimen is ductile frac- ture.However,for the thicker specimen (WOL),plastic deformation and cracking mainly occurs in the pearlite colony,which results in cleavage fracture. KEY WORDS wheel steel;in-situ tension:plastic deformation zone;microcrackWear properties of reactive plasma clad （CrFe）7C3／γ－Fe ceramal composite coatings LIU Junbo 12）WA NG L imei 3）HUA NG Jihua 2） 1） Department of Mechanical and Electronic EngineeringWeifang UniversityWeifang261041China 2） Materials Science and Engineering SchoolUniversity of Science and Technology BeijingBeijing100083China 3） Department of Information and Control EngineeringWeifang UniversityWeifang261061China ABSTRACT An in-situ reinforcing phase （CrFe）7C3ceramal composite coating was fabricated on the substrate of a0∙45％ carbon steel using Fe－Cr－C elemental powder blending by reactive plasma clad process．The microstructure and micro-hardness of the coating were evaluated by SEMXRDEDS and micro-hardness instrumentthe room temperature and high temperature wear properties were evaluated under dry sliding wear test conditionsand the wear mechanism was discussed．The results indicated that the reactive plasma clad ceramal composite coating has a rapidly solidified microstructure consisting of primary （CrFe）7C3 and （CrFe）7C3／γ－ Fe eutecticswith excellent wear properties under both room-temperature and high-temperature sliding wear test conditions． KEY WORDS ceramal composite coating；reactive plasma clad；microstructure；wear properties （上接第38页） In situ study of deformation and fracture process in wheel steel and effect of hydrogen SHI Dongmei 1）LI Jinxu 1）DUA N Guihua 1）REN Xuechong 1）CHU W uyang 1）QIAO L ijie 1） JIA NG Bo 2）CHEN Gang 2）CUI Y inhui 2） 1） Materials Science and Engineering SchoolUniversity of Science and Technology BeijingBeijing100083China 2） Technology Center of Ma’anshan Steel ＆ Iron CorporationMa’anshan432000China ABSTRACT In situ tensile tests in scanning electron microscope （SEM） were carried out using single-edge notched specimens of no larger than0∙5mm in thickness made of CL60wheel steel with or without hydrogen charging．Observations under optical microscope （OM） were also done to a wedge opening-loading （WOL） specimen with a thickness of30mm which was precracked．The result shows thatfor the thinner specimenplastic deformation occurs firstly in proeutectoid ferrite and then grows along the prior austenite grain boundaryand thena microcrack initiates and propagates preferentially at the interface of proeutectoid ferrite and pearlite colony．The process of deformation and fracture is almost same each other for both specimens with and without hydrogenexcept that the microcrack initiates more frequently by way of inclusion separating and shelling from matrix for the specimen with hydrogen．The fracture surface fractograph of the thinner specimen is ductile fracture．Howeverfor the thicker specimen （WOL）plastic deformation and cracking mainly occurs in the pearlite colonywhich results in cleavage fracture． KEY WORDS wheel steel；in-situ tension；plastic deformation zone；microcrack ·54· 北 京 科 技 大 学 学 报 第29卷