Microstructure and high temperature tribological behavior of laser cladding Ni60A alloys coatings on 45 steel substrate

The crack-free Ni60 A coating was fabricated on 45 steel substrate by laser cladding and the microstructure including solidification characteristics, phases constitution and phase distribution was systematically investigated. The high temperature friction and wear behavior of the cladding coating and substrate sliding against GCr15 ball under different loads was systematically evaluated. It was found that the coating has homogenous and fine microstructure consisting of γ（Ni） solid solution, a considerable amount of network Ni-Ni3 B eutectics, m^23C6 with the floret-shape structure and Cr B with the dark spot-shape structure uniformly distributing in interdendritic eutectics. The microhardness of the coating is about 2.6 times as much as that of the substrate. The coating produces higher friction values than the substrate under the same load condition, but the friction process on the coating keeps relatively stable. Wear rates of the coating are about 1/6.2 of that of the substrate under the higher load（300 g）. Wear mechanism of the substrate includes adhesion wear, abrasive wear, severe plastic deformation and oxidation wear, while that of the coating is merely a combination of mild abrasive wear and moderate oxidation wear.

Effect of initial deposition behavior on properties of electroless Ni-P coating on ZK60 and ME20 magnesium alloys

The composition of magnesium alloys is greatly associated with initial deposition behavior of electroless Ni-P coatings.Thus,the initial deposition behavior of electroless Ni–P coatings on ZK60 and ME20 alloys was investigated.The results indicated that differences in the alloy compositions significantly influenced the initial deposition process and the adhesive strength,corrosion resistance,and crystal structure.The initial deposition of coatings on ZK60 and ME20 alloys preferentially occurred on the precipitates.The precipitates in ZK60 alloy had higher chemical activity after HF activation and controlled the initial deposition rate of the coating.The initial deposition rate of the coating on ME20 alloy mainly depended on the density of the Mg F2 film formed by HF activation rather than on the precipitates.Owing to differences in the initial deposition process,the coating on ZK60 alloy had higher adhesive strength and better corrosion resistance than that on ME20 alloy.The coatings on ZK60 and ME20 alloys mainly had crystalline structures,and the coating on ME20 alloy had also a slight microcrystalline structure.

THE MULTI-LAYER LASER CLADDING OF Ni60 ALLOY

The Multi layer coating of Ni60 alloy was got by multi layer laser cladding. The height of the coating was about 12mm and the wall of the coating was perpendicular to the base. The microstructure of the coating was made up of fine dendrite. The conjunction between layers was good.

Magnetization-Enhanced Dislocation Motion and Decreased Yield Strength of 60Fe40Ni Alloy

Using a special constant deflection device, the changes in dislocation configuration ahead of a loaded crack tip for 60Fe40Ni alloy. before and after magnetization in a magnetic field, have been studied in TEM. The results showed that the magnetization for 60Fe40Ni alloy could enhance dislocation emission, multiplication and motion. Also, the mechanical properties of 60Fe40Ni alloy, in air and in the magnetic field respectively have been investigated using the slow strain rate tension. And the results indicated that magnetization could make the yield strength corresponding to decrease by 26 percent, but did not influence the ultimate tensile strength and the fracture strain, which showed that magnetization could enhance plastic deformation.

铝合金表面等离子喷涂镍基涂层的耐磨损腐蚀行为

采用等离子喷涂技术在7075铝合金基体上制备了Ni 60+35%WC合金涂层,通过光学显微镜及数字显微硬度计对涂层形貌及力学性能进行了表征。通过UMT-5摩擦试验机对基体试样和涂层试样进行了摩擦试验;通过向高压釜中冲氮气模拟不同静水压力,结合电化学技术测试涂层在不同静水压力3.5%NaCl溶液中的耐蚀性。结果表明:Ni 60+35%WC涂层结构致密,孔隙和裂纹少,涂层与铝合金的结合属于机械结合,涂层的硬度远高于铝合金基体;涂层的磨损率远低于铝合金基体。随着静水压力的增大,涂层及基体在3.5%NaCl溶液中的耐蚀性均降低。

SCF-Xα-SW程序和LMTO程序的改进及其在固体体系中的应用

在ＹＨ１／ＹＨ２计算机上将多重散射Ｘα自洽场方法（ＳＣＦＸαＳＷ）程序和线性Ｍｕｆｉｎｔｉｎ轨道方法（ＬＭＴＯ）程序做了改进，实现了向量化和并行化。研究了Ｃ６０的能级；计算了苯分子从１ｅ１ｇ，２ｅ２ｇ和１ａ２ｕ开始激发的１０８个Ｒｙｄｂｅｒｇ态单电子轨道激发能，即１ｅ１ｇ，２ｅ２ｇ，１ａ２ｕ→ｋａ１ｇ（ｋ＝３－１１），ｋｅ２ｇ（ｋ＝２－７），ｋｅ１ｕ（ｋ＝３－８），ｋｅ１ｇ（ｋ＝２－５），ｋｅ２ｇ（ｋ＝３－５），ｋｅ２ｕ（ｋ＝２－３），ｋｂ２ｕ（ｋ＝２－３），ｋｂ１ｕ（ｋ＝２－３），１ｂ１ｇ，１ｂ２ｇ；