原位冶金法制备 WC／Ni 复合材料的形貌特性及性能研究

研究了采用直流电弧原位冶金技术制备 WC ／Ni 复合材料的方法和组织性能。试验结果表明,生成的WC 颗粒在制备的 WC ／Ni 复合材料的底部和顶部中的分布和尺寸都不同,底部分布较少并成散乱分布,尺寸达到100～200μm;顶部分布较多且有序分布,尺寸为10～20μm。基体为 Al0．9 Ni4．22相且硬度整体一致,WC 组织颗粒的宏观形貌为三棱柱,微观则为层片状结构,且其硬度根据所处位置不同而有一定变化,最大值可达到2331.99 HV。     

激光熔覆Ni基WC涂层内铸造WC颗粒溶解特征的研究

采用激光熔覆的方法在Q235钢表面制备了wc颗粒强化的Ni基涂层。研究了铸造wc颗粒在涂层内的溶解特征。结果表明：铸造wc颗粒在涂层底部几乎完全溶解并与扩散进入的Fe发生共晶反应形成粗大的鱼骨状形貌特征M6C型碳化物;在涂层中部,铸造wc颗粒完全溶解并析出M7C3,M12C与M23C6型碳化物;在涂层边部,大部分铸造wc颗粒发生部分溶解形成3—5μm的M6C合金化反应层,保持了原有多角状结构与高硬度特征。     

不同Co含量对超音速火焰喷涂WC-xCo-3Cr涂层组织和性能的影响

通过超音速火焰喷涂工艺在Cr12模具钢表面上喷涂制备了WC-x Co-3Cr(x=8,10,12,14)涂层,并采用金相显微镜、扫描电镜、显微硬度仪和摩擦磨损试验机表征分析涂层的微观结构、显微硬度、耐磨损性能和耐腐蚀性,考察了不同Co含量对涂层组织和性能的影响。结果表明,Cr12模具钢超音速火焰喷涂后表面的耐磨损性能比喷涂前的基体耐磨损性能有较大的提高;表面硬度在不同程度上都得到提高,界面结合良好,其中WC-10Co-3Cr涂层的组织致密性最好、显微硬度最高、耐磨损及耐腐蚀性能最好。     

Value differences in foreign students

The Rokeach Value Survey was administered to four equivalent groups of students studying in London. It was hypothesized that a number of differences would occur between these groups based on their country of origin, respective affluence and traditional cultural values. Half of the values showed significant differences between groups with the British Control Group and the Europeans being most often more similar to each other than the other groups. The Africans were most different from the three other groups. These results were interpreted in terms of cultural and economic differences and related specifically to the literature of sojourner adjustment. Limitations of the research are also noted.     

On the relevance of signal detection theory to the correction for guessing

This paper shows how alternatives to the conventional guessing correction may be derived from considerations similar to the signal detection theory of psychophysics. Methods of experimentally determining the right correction are briefly suggested.     

超音速火焰喷涂在流体机械中的应用

介绍了超音速火焰喷涂装置的结构组成和工作原理,喷涂零件处理方法和应用效果。超音速火焰喷涂提高了水轮机、阀门等流体机械过流部件的抗磨蚀性能,已经成为目前国内外普遍采用的抗磨蚀工艺,在某些水电厂河流泥沙、水泥浆矿物体、硅粉等行业恶劣工况中得到了实际应用,并取得了良好的综合效益,具有较高的推广价值。     

WC弥散强化铜的物理性能

文章介绍了WC弥散强化铜的制备过程，通过比较WC弥散强化铜和纯铜的有关性能（硬度、电阻率、密度），指出WC弥散强化铜是一种有潜力的强化铜，且当浇结温度为950℃，WC的体积分数为1.2%时，弥散强化铜的综合性能较好。     

Influence of Heat Treatment on Microstructure and Sliding Wear Behavior of Fe-Al/WC Composite Coatings

Researchershavebecomeincreasinglyinterestedinironaluminideintermetallics (includingFe3AlandFeAl)since 1970sinviewofthecombinationoflowcost,lowerdensity ,remarkableresistancetoerosion ,sulfidizingandoxidizingathightemperature .However ,industrialap plicationofthesealloyshasbeenverylimitedduetotheirpoorductilityandfracturetoughnessatroomtemperatureaswellastheirdifficultyinshaping[1] .Somestudieshaveindicatedthatcoatingstructuralmaterialswithironaluminidesbyusingthermalsprayingwillnotonlysolveth…     

激光熔覆制备纳米WC/Co复合涂层的研究

采用横流2．0kwCO2激光器，在45号钢表面制备了表面较平整、较细密、基本消除了裂纹与孔隙并与基体呈冶金结合的纳米WC／Co复合涂层。通过SEM，EDAX，XRD，AFM及NanoIndenterXP分析了熔覆层的显微组织、成分、物相及结合强度。结果表明，涂层的显微组织为涂层中镶嵌着大量与Ni基合金结合良好的WC／Co颗粒，其中在原子力显微镜下可见相当数量的粒度≤100nm的纳米颗粒。涂层的结合强度比传统热喷涂提高了2．3倍。涂层中纳米WC／Co在激光熔覆中的纳米效应起着重要作用。