硬质合金耐磨堆焊材料断裂与韧性的研究

通过对不同类型硬质合金复合耐磨堆焊材料冲击试验的研究,探讨了影响堆焊层韧性的因素,观察分析了其断口形貌和断裂机理,结果表明,堆焊材料的冲击韧性与断口上硬质合金颗粒的面积分数、堆焊方法以及基体金属的显微组织有关,主要取决基体金属韧性和含量,基体金属的韧性越好,含量越多,堆焊材料的韧性越高,在冲击载荷作用下,基体金属断裂表现为高塑性的韧窝断裂,且存在一定撕裂棱,而硬质合金的断裂为脆性穿晶解理断裂或沿晶断裂。     

牙轮钻头强化用YQ4堆焊层组织性能研究

利用自主开发Ni-Cr-B-Si-Cu合金粉研制了YQ4堆焊焊条,采用氧乙炔堆焊工艺制作了堆焊试样,利用剪切实验测试了堆焊层强度,冲击磨料磨损实验测试了试样的耐磨性,利用扫描电子显微镜观察了断口显微组织特征.实验结果表明:YQ4硬质合金堆焊层中过渡层组织细小,耐磨层中脆性硬质合金相上均匀分布了韧性微孔结构低熔点合金,硬质合金分布致密、均匀、多层堆垛,基体与过渡层以及硬质合金之间结合良好,平均剪切强度600 MPa,高于牙轮钻头工作要求,抗冲击磨料磨损能力提高近2倍,在组织与性能上都满足牙轮钻头齿面强化要求.     

锰对厚大断面球铁力学性能和断裂韧性的影响

研究了锰对厚大断面球铁的力学性能及断裂韧性的影响.研究结果表明,锰含量的增加导致试块心部的珠光体含量相对较高,在一定程度上缓解了由石墨形态恶化所造成的抗拉强度下降.随着冷却凝固速度的降低和锰含量的增加,冲击断口形貌和断裂韧性断口形貌由韧-脆混合型断口裂转变为脆性断口.利用扫描电镜动态拉伸原位厚大断面球铁中不同基体组织的断裂过程,珠光体在外力作用下比铁素体容易萌生裂纹,裂纹往往沿着相邻的珠光体团交界扩展.珠光体的塑韧性较低且脆性大.厚大断面球铁中控制珠光体含量,提高铁素体含量,可提高球铁塑韧性.     

碳纳米管增强钛铝基复合材料的组织与性能

采用激光熔铸技术制备碳纳米管增强钛铝合金复合材料,对铸块的组织、结构及断口形貌进行分析。结果表明：铸块的基体主相为TiAl,Ti3Al合金,碳纳米管细化了基体组织晶粒,适量的碳纳米管提高了材料的硬度和韧性,w（CNTs）=1．5％时,复合材料显微硬度（738HV）与相同条件下基体合金硬度（647HV）相比提高了14％,材料断口为韧性断裂。     

亚微细硬质合金三牙轮钻齿的使用与失效分析

将钴含量为13％的亚微细晶粒硬质合金钻齿应用到81／2XA537三牙轮钻头上，并运用扫描电镜和光学显微镜等手段对亚微细晶粒硬质合金钻齿进行了失效分析。分析发现81／2XA537钻头的主要失效形式为崩齿和断齿。在断口分析的基础上，提出了亚微细硬质合金断裂机理为沿晶断裂，而常规硬质合金的断裂机理为穿晶断裂。由于生产工艺问题亚微细合金内部存在粗大的WC晶粒、晶粒偏析以及微裂纹，这些内部缺陷的存在使亚微细合金出现早期失效。     

SiC_f/Ti_2AlNb复合材料高温拉伸断裂行为研究

选用SiC纤维作为增强体,Ti_2AlNb合金为基体,采用磁控溅射法并结合热等静压工艺制备纤维体积分数为50%的SiC_f/Ti_2AlNb复合材料。通过观察该材料的断口表面及断口附近剖面形貌,研究SiC_f/Ti_2AlNb复合材料在750℃高温的拉伸断裂损伤及断裂过程。研究发现,SiC_f/Ti_2AlNb复合材料断口形貌复杂,在高温拉伸实验过程中,复合材料存在的断裂损伤有界面反应层多次断裂、界面脱粘、纤维二次断裂、基体塑性变形、基体韧性断裂、纤维拔出和W芯"拔出"。     

YG20C硬质合金冷镦模疲劳断口的电镜研究

作者利用x射线能谱仪对YG20C硬质合金冷镦模进行了成分分析。通过x射线衍射,鉴定了合金的粘结相为βCO。它具有面心立方结构,韧性较好。利用扫描电镜和透射电镜对镦模疲劳断口的宏观和微观形貌进行了仔细的观察研究,并借助于背散电子像测量了WC的颗粒度。作者认为:高钴粗晶粒硬质合金的疲劳裂纹是在韧性的钴相中发展,故冷镦模的疲劳断裂具有一般韧性金属高波周疲劳的特征。     

AA6082铝合金MIG焊接接头组织和疲劳性能分析

采用光学显微镜、扫描电子显微镜、疲劳试验机、显微硬度计等对AA6082铝合金焊接接头的微观组织、显微硬度和疲劳断口特征进行研究.结果表明:焊缝主要为树状晶的铸态组织,熔合区为柱状晶,母材显微组织中α(Al)固溶体基体上均匀分布着强化相Mg_2Si.接头热影响区宽度达到14 mm,存在软化区.对疲劳断口进行微观和宏观分析发现,AA6082铝合金熔化极惰性气体保护(MIG)焊接接头的断口具有解理断裂的特征,同时也有少量的韧性断裂特征,断口中存在解理台阶、韧窝和大量长短不等的二次裂纹.     

45钢堆焊金属组织及显微硬度研究

分别采用D237和D207两种堆焊焊条,以焊条电弧焊工艺在基体材料45钢上进行堆焊,对在相同焊接条件下获得的堆焊金属的显微组织和显微硬度进行了分析,并讨论了合金元素对堆焊层显微组织及显微硬度的影响.结果表明:堆焊层金属的显微组织及显微硬度与焊接线能量有关,与焊条的合金成分及含量有关,与其硬质相的类型、性能及分布等有关;合金元素钼、钒对堆焊金属品粒的细化作用效果明显.     

TiC,NbC,VC,B4C超硬质相耐磨堆焊材料的研究

采用钛、铌、钒、硼等铁合金与石墨等材料的混合粉,用TiC,B_4C硬质合金与F101,F314等自溶合金制成混合复合材料,以等离子转移电弧为热源进行了探索性的耐磨堆焊材料的试验研究。通过堆焊时的冶金反应,在堆焊金属中形成了TiC,NbC,VC等碳化物超硬质相,极大的提高了堆焊金属的硬度和耐磨性。试验数据表明,这种堆焊金属的耐磨性均超过国内目前F31,堆667,堆717堆焊材料的耐磨性,为堆焊材料领域开发新型材料提供了新的途径。     

高铬铸铁型自保护药芯焊丝堆焊组织与性能分析

研制了一种自保护高铬铸铁型药芯焊丝,对其堆焊金属组织与性能进行了分析,结果表明：堆焊金属表面硬度达到HRC60以上,堆焊金属显微组织主要为马氏体＋残余奥氏体＋M7C3型碳化物;初生碳化物主要沿堆焊层向母材方向生长,其表面硬度为HV1783,侧面为HV1127;共晶碳化物围绕在初生碳化物周围生长,其显微硬度为HV830;在相同磨损条件下磨损1h后,堆焊金属相对耐磨性为Q235钢的14倍左右,在药芯中加入适量的稀土氧化物能提高堆焊金属的耐磨性。     

Effect of Titanium Content on Microstructure and Wear Resistance of Hardfacing Alloy

The hardfacing alloys with different concentrations of titanium were deposited on carbon steel substrates by shielded metal arc welding, and the effect of titanium content on the microstructure characteristics of the hardfacing alloys was investigated. The wear resistance test of the hardfacing alloys was carried out by using a slurry rubber wheel abrasion test machine, and the wear behaviour was also studied. The results indicate that the addition of titanium can effectively promote the precipitation of the complex carbides of Nb and Ti due to the prior precipitation of titanium carbide which acts as nucleation sites for complex carbides. With the increase of titanium content, the wear resistance of the hardfacing alloys is increased gradually resulting from the refinement of microstructure and dispersive distribution of fine carbide precipitates. And the wear mechanism is mainly minimum plastic deformation with interrupted grooves due to the strengthening and protecting effects of carbide precipitates.     

Influence of Thermal Load on Mechanical Property of Cemented Carbide Material and Heavy Cemented Carbide Inserts Life

A large amount of cutting heat is produced during the heavy cutting process,and insert life is restricted by the effect of thermal load.The thermal load experiment of cemented carbide SCS,WF and YT15 is carried out,and the results show that the bending strength and fracture toughness of cemented carbide material decrease obviously under cyclic thermal load,while in the cooling process,the material mechanical property changes worse suddenly.The high-temperature mechanical property of SCS is the most stable,and that of YT15 is the worst.Further,a relation model among cutting temperature,cutting parameters and insert life is established.Finally,the measures to improve heavy cemented carbide inserts life are summarized from the aspects of cutting parameters selection,insert optimization design and TiCN,Al2O3,TiN complex insert coating.The research results are expected to provide support and reference for heavy cutting technology and insert technology.     

07MnNiCrMoVDR钢焊缝组织与低温冲击韧性分析

采用SMAW焊接工艺焊接低合金高强度07MnNiCrMoVDR钢获得焊接接头,通过焊缝显微组织观察、冲击断口分析、焊缝低温冲击试验,研究了07MnNiCrMoVDR钢焊缝组织与低温冲击韧性。结果表明,焊缝组织由沿晶界分布的先共析铁素体、晶内的针状铁素体和粒状贝氏体构成,针状铁素体以微夹杂物为核心生长。温度为－40 ℃时,不同部位焊缝冲击吸收功随试样截取深度的增大而减小;与近表面处相比,1/2厚度处焊缝冲击吸收功损失约67%,在1/4厚度处,焊缝冲击吸收功随着温度的降低而降低;焊缝的低温冲击韧性符合要求。焊缝冲击断口的表面由凹凸不平变得比较平整,断口的微观形貌由韧窝花样变成解理河流花样。     

Microstructures and properties of WC-20Co-1Y_2O_3 cemented carbide by hot-press and liquid phase sintering

1　INTRODUCTIONInRef .[1],averyinterestingandinexplicablefindingwasreportedthataspecialwhisker likeWCgrainstructure ,mostintherangeof 10 0 2 0 0nmindiameterand 1 2mminlength ,wasformedinWC 2 0Co 1Y2 O3cementedcarbidepreparedbyhot pressbelowtheeutectictemperature .ItwasmentionedinthepaperthatWCpowderwithFisherSubsiereSizer(FSSS)of 1μm ,ultrafineCopowder ,andY2 O3powderof 1μmwereusedastherawmaterialsofWC 8Cocementedcarbide .However ,whetherthesamerawmaterialswereusedinWC 2 0Co …     

Toughening modification of unsaturated polyester resin using HDI trimer

HDI trimer was firstly used to improve the mechanical properties of hydroxyl- terminated unsaturated polyester (UP). Mechanical properties measurements performed on the cured materials demonstrate a distinct improvement in intensity and toughness in the presence of HDI trimer and shows the change trends of increase and then decrease. The morphological analysis of the fracture surfaces shows that the micro-phase separated structures appear in modified UPR systems and changed from dendritric, dimple and to cystiform structures with the increase of HDI trimer content. The presence of the cystiform structures made the modified UPR systems present the best properties. Funded by the Hubei Provincial Natural Science Fundation of China (No.2006ABA321)     

Microstructures and properties of WC-2OCo-1Y2O3 cemented carbide by hot-press and liquid phase sintering

Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake (uneven-ly distributed binder phase), and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2 O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.     

硬质合金中温钎焊技术的实验研究

采用显微结构法,通过观察钎焊接头形成条件,研究了以B-Ag-1为钎料的硬质合金和钢的中温连接技术。实验表明,在感应电流为450～600 A时,B-Ag-1钎料能湿润并在硬质合金上铺展,形成组织均匀的钎缝,同时通过钎料中银原子和铜原子向硬质合金的扩散形成具有一定强度的界面。钎焊温度的降低以及铜缓冲层的加入,大大降低了钎焊过程的热应力,接头和母材上均未发现热裂纹。     

硬质合金中温钎焊技术的实验研究

采用显微结构法,通过观察钎焊接头形成条件,研究了以B-Ag-1为钎料的硬质合金和钢的中温连接技术。实验表明,在感应电流为450～600 A时,B-Ag-1钎料能湿润并在硬质合金上铺展,形成组织均匀的钎缝,同时通过钎料中银原子和铜原子向硬质合金的扩散形成具有一定强度的界面。钎焊温度的降低以及铜缓冲层的加入,大大降低了钎焊过程的热应力,接头和母材上均未发现热裂纹。