INFLUENCE OF SURFACE MORPHOLOGY ON THE MICROHARDNESS OF ELECTROLESS Ni-B DEPOSIT REVEALED BY AFM OBSERVATION

Introduction　　 Electroless Ni- B alloy has many advantagessuch as superior hardness,excellent wear- resis-tance and some special electrical and magneticproperties[1,2 ] . It can be prepared with eitherDimethylamineborane( DMAB) or sodium borohy-dride as reductant[3 ,4] .The deposits with lowerboron contentwhich are mainly applied to electron-ic industry[5] are prepared by DMAB.While sodi-um borohydride can bring about higher boron con-tent deposits which are chiefly used as wear- resis-…     

INFLUENCE OF SURFACE MORPHOLOGY ON THE MICROHARDNESS OF ELECTROLEESS NI-B DEPOSIT REVEALED BY AFM OBSERVATION

A crystalline and non-crystalline two-phase Ni-B coating was prepared by electroless deposition with potassium borohydride as reducing agent. When the deposit was heated from 10 C to 500 C, it took place three kinds of phase transformation and formed corresponding nickel borides. An Atomic Force Microscopy (AFM) was used to directly view the surface morphologies of the samples in various treated states. The AFM images indicate that nano-dimensional protrusions grow on the surface of the deposit grain during some heat treatment processes,and they are distinguished greatly from the small bulges existing in the as-plated deposit. Further studies show that the microhardness related to the surface topography of thecoating to some extent. Especially when a two-step heat treatment process was performed, the nano-dimensional protrusions on the grain surface grew upt to 40～100nm in diameter and 10～20 nm in height, and the deposit microhardness reached up to HV1500～ 1600 in the meantime.     

潜射导弹综合保障仿真评估研究

综合保障的实践表明,保障任务的核心问题就是如何维护复杂装备的系统可靠度和运行可用度,综合保障仿真评估是衡量保障效果既经济又切实可行的方法。针对潜射导弹武器系统特点,建立了基于任务时间线的仿真模型,提出了仿真系统总体结构及设计思想,分析了仿真流程,说明具体实现方法。最后,以某型潜射导弹为原型进行实例验证,仿真结果表明所建模型能够很好的反映装备实际组成和运行情况。     

Technology Problems of Laser Cladding Procedure for in-situ TiCp／Al Composite Layer on Aluminum Alloy

IntroductionLaser cladding on aluminum alloy surface is avalid means to improve its surface characteristic.In the past researches,the self- molten alloys wereusually used for laser claddings to improve surfacewear resistance of aluminum alloys[1,2 ] .However,owing to great difference of heat expansion coeffi-cients between aluminum alloy substrate and cladmaterials,such as Ni- Cr- Si- B,Ni- Cr- Al,the big-ger strain in clad layer is formed during solidifica-tion,which results in a lot of cr…