激光熔覆层表面皱折成因的研究

本文就激光熔覆过程中,熔覆层表面极易出现的波纹皱折等缺陷的成因及解决途径进行了深入的分析研究。     

Cr12MoV钢表面激光熔覆Ni60合金制备无开裂涂层及摩擦磨损性能研究

为了实现损伤Cr12MoV钢激光再制造,采用激光熔覆Ni60合金制备无开裂涂层。利用着色探伤剂、硬度计、光学显微镜(OM)、X射线衍射仪(XRD)和摩擦磨损仪对所制备Ni60合金涂层的表面开裂、硬度、金相组织进行分析,并用摩擦磨损试验机对比研究了Ni60合金涂层和Cr12MoV钢的摩擦磨损性能。结果表明,当Ni60合金涂层长度L≤9 mm时,涂层表面无开裂;当Ni60合金涂层长度L>9 mm时,开裂区出现在母材邻近区,且随着涂层长度增大,开裂区也出现在涂层表面。要抑制激光熔覆过程中Ni60合金近母材区开裂,关键在于减少热输入对母材区的作用时间。最后,通过优选表面硬度相近的Ni60合金涂层和Cr12MoV钢进行摩擦磨损性能测试,发现两者的摩擦系数与耐磨性能相近,可望为损伤Cr12MoV钢激光再制造提供参考。     

Influence of rapid quenching on cyclic stability of La-Mg-Ni system （AB3-type） electrode alloys

Aiming at the improvement of the cyclic stability of La-Mg-Ni system （PuNi3-type） hydrogen storage alloy, Ni in the alloy was partly substituted by Fe. The electrode alloys of La0.7Mg0.3Co0.45Ni255-xFex （x=0, 0.1, 0.2, 0.3, 0.4） were prepared by casting and rapid quenching. The influence of the quenching on cyclic stability as well as structure of the alloys was investigated in detail. The results of electrochemical measurement indicated that rapid quenching significantly improved cyclic stability. When the quenching rate rose from 0 （As-cast was defined as a quenching rate of 0 m/s） to 30 m/s, the cyclic life of Fe-free alloy （x=-0） increased from 81 to 105 cycles, and for alloy containing Fe（x=0.4）, it grew from 106 to 166 cycles at a current density of 600 mA/g. The results obtained by XRD, TEM and SEM revealed that the as-cast and quenched alloys had multiphase structures, including two major phases （La, Mg）Ni3 and LaNi5 as well as an imptLrity phase LaNi2. Rapid quenching helped the formation of an amorphous-like structure in Fe containing alloys.     

Influences of melt spinning on electrochemical hydrogen storage performance of nanocrystalline and amorphous Mg2Ni-type alloys

In order to improve the electrochemical hydrogen storage performance of the Mg₂Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg₂Ni-type Mg_20−x La _x Ni₁₀ (x=0, 2) alloys were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage properties of the experimental alloys were tested. The results show that no amorphous phase is detected in the as-spun Mg₂₀Ni₁₀ alloy, but the as-spun Mg₁₈La₂Ni₁₀ alloy holds a major amorphous phase. As La content increases from 0 to 2, the maximum discharge capacity of the as-spun (20 m/s) alloys rises from 96.5 to 387.1 mA·h/g, and the capacity retaining rate (S ₂₀) at the 20th cycle grows from 31.3% to 71.7%. Melt-spinning engenders an impactful effect on the electrochemical hydrogen storage performances of the alloys. With the increase in the spinning rate from 0 to 30 m/s, the maximum discharge capacity increases from 30.3 to 135.5 mA·h/g for the Mg₂₀Ni₁₀ alloy, and from 197.2 to 406.5 mA·h/g for the Mg₁₈La₂Ni₁₀ alloy. The capacity retaining rate (S ₂₀) of the Mg₂₀Ni₁₀ alloy at the 20th cycle slightly falls from 36.7% to 27.1%, but it markedly mounts up from 37.3% to 78.3% for the Mg₁₈La₂Ni₁₀ alloy.     

影响贮氢合金电化学性能测试结果的因素——循环次数和充放电制度

较系统地研究了循环次数和充放电制度对贮氢合金电极片的电化学行为产生的影响以及测试时应注意的问题,如测量贮氢合金的放电容量和电压特性一般应在第２５次～３０次循环左右进行、以充放电次数表达的活化速度需注明充放电制度以及测量大电流放电特性应避开小电流放电后的最近几次循环等。     

多冲接触载荷下不锈钢零件激光表面熔覆层组织及其失效行为

采用5kW大功率激光器在不锈钢基材上熔覆Co基合金，制取的涂层质量优于传统的电弧、火焰堆焊以及等离子喷焊工制取的涂层。对氮肥生产上甲胺泵中的进排液组合阀多冲接触表面进行激光熔覆，成功地实现了传统工艺难以完成的涂层强化工艺，上线应用证明其抗多冲接触载荷的明显增强。承受多冲接触载荷的表面强化涂层质量与强化工艺、基体和涂层材料、涂层厚度等有关。涂层厚度应根据多冲接触载荷的性质、应力大小、基体等情况来决定，太薄的涂层会造成或加剧涂层开裂、塌陷等失效行为。激光熔覆为工程中承受多冲载荷的重要零部件表面强化提供了一种更好的工艺方法。     

铸态低钴贮氢合金RE(NiCoMnAlCu)5.1的电化学性能

研究了一系列低钴贮氢合金RE(NiCoAlMnCu)5．1合金的电化学性能。实验发现，稀土中La和Ce含量的变化对合金的放电容量和循环稳定性均有影响，一般是La含量较高的合金最大放电容量也较大，而Ce含量较高的合金循环稳定性较好，活化性和1C放电性能却相差不大。实验结果表明，通过调节混合稀土成分可以使得RE(NiCoMnAlCu)5．1稀土贮氢合金具有良好的综合电化学性能。     

金属功能材料的新近发展

简要介绍了金属功能材料的基本内容、特点和地位，重点论述了国内外几类研究和应用开发比较活跃的新材料领域；讨论了我国金属功能材料的开发简况和发展方向。     

准贝氏体钢渗碳层耐磨性及磨损机制研究

研究了准贝氏体钢销盘磨料磨损和冲击磨料磨损的耐磨性和磨损机制，确定了回火温度对耐磨性的影响，探讨了残余奥氏体的机械稳定性及其对耐磨性的作用。结果表明：准贝氏体钢渗碳层的耐磨性接近或优于18Cr2Ni4WA钢；以微切削型磨料磨损为主的准贝氏体钢渗碳件，宜采用180℃回火，以应变疲劳型磨料磨损为主的准贝氏体钢渗碳件，宜采用280℃回火；残余奥氏体的机械稳定性对材料的耐磨性具有重要作用。对于微切削型磨料磨损，机械稳定性高的残余奥氏体不利于提高耐磨性；对于应变疲劳型磨料磨损，机械稳定性高的残余奥氏体明显提高耐磨性。     

镁基贮氢合金的制备

综述了镁基贮氢合金制备方法的研究进展，对熔炼法、机械合金化法、扩散法、氢化燃烧法、表面处理等几种主要制备镁基贮氢合金的方法的制备过程、影响因素、特点、优缺点等作了阐述，并论述了目前国内外采用不同制备方法所制得的部分镁基贮氢合金的充放氢性能和电化学性能。