hBN含量对等离子喷涂NiCr/Cr_3C_2-hBN复合涂层力学性能的影响

采用化工冶金包覆、喷雾造粒和固相合金化技术以Cr3C2和hBN为核心制备了NiCr/Cr3C2-h BN复合粉体,并用等离子喷涂技术制备了NiCr/Cr3C2-hBN涂层,研究了涂层的显微结构、物相组成、显微硬度和结合强度。研究结果表明,等离子喷涂NiCr/Cr3C2-h BN复合涂层呈典型的层状结构,各层之间结合良好。涂层的显微硬度和结合强度均随hBN含量的增加逐渐降低,当hBN含量为20%时,涂层的显微硬度和结合强度分别为NiCr/Cr3C2涂层的66%和50%。涂层断裂位置发生在涂层内部,为典型的脆性断裂。     

激光冲击改善W6M05Cr4V2(M2)高速钢刀具材料耐磨性的研究

目的 研究激光冲击强化(LSP)技术对M2高速钢材料表面抗磨损性能的影响.方法 采用高功率短脉冲的强激光束对M2试样进行激光冲击处理,然后用显微硬度计测量试样冲击区横截面上的纵向显微硬度,用磨损试验机对冲击处理前后的试样进行磨损实验.结果 在铝箔涂层、流水约束层作用下对M2高速钢试样进行激光冲击强化处理,试样强化层中的奥氏体晶粒显著细化.试样冲击区横截面上形成了由表及里的纵向显微硬度梯度,获得了深约0.6 mm的硬化层,表层材料显微硬度峰值高达70HRC左右,比基体硬度提高10％左右.激光冲击处理后的M2试样表面较光洁,磨痕较少,磨痕底部相对平滑,犁沟深度较浅,磨损量较小,稳定磨损阶段较长,表面呈现较好的抗咬合性和较高的耐磨性.结论 经激光冲击处理后,M2高速钢材料强化层所获得的较细晶粒和较高硬度有效改善了表面抗磨损性能,进一步提高了M2高速钢刀具的切削性能与使用寿命.     

强制冷却对IC10合金激光熔覆组织与硬度的影响

为实现IC10定向凝固高温合金高效、高质量的激光熔覆,开发了通水冷却装置实现激光熔覆过程中的强制冷却,研究了不同冷却条件对激光熔覆层定向凝固组织生长和硬度的影响. 结果表明,相较于无冷却条件,在同样激光熔覆工艺参数下采用强制冷却进行激光熔覆会改变熔覆层形貌,并提高柱状晶在熔覆层中的体积分数,有助于得到更多定向连续生长的柱状晶. 此外,强制冷却对于熔覆层各区域硬度无明显影响,但由于强制冷却条件下熔覆层中柱状晶增多,因此高硬度区域增大.     

激光表面处理1.6%C超高碳钢的组织与性能

为了研究激光处理后超高碳钢表面组织及性能的变化,采用2kW连续横流CO2激光器对超高碳钢(C的质量分数为0.016)进行了激光处理,采用扫描电镜观察组织和显微硬度计测量深度方向显微硬度值的方法,进行了理论分析和实验验证,取得了沿深度方向的组织照片和硬度分布曲线。结果表明,激光处理层分为熔凝层、过热层和相变硬化层。熔凝层可观察到胞状树枝晶和离异共晶;相变硬化层组织细小,显微硬度(高达750HV～905HV)高于其它层,是典型的激光淬火组织。随激光功率增大(1000W～1200W),熔凝层中胞状树枝晶和离异共晶增多并细化,马氏体数量减少,各层的宽度、深度均增大,显微硬度降低。这一结果对细化超高碳钢组织和改善其性能是有帮助的。     

拉-拉疲劳载荷对孔壁强度的影响

在疲劳断裂的中心圆孔试样孔壁取样进行显微硬度与残余应力的测试,结合有限元模拟结果对测试数据进行分析,从孔壁强度变化的角度研究孔零件在拉-拉载荷作用下发生疲劳断裂的原因。结果表明:疲劳断裂中心圆孔试样孔壁出现显微硬度梯度,长度方向孔壁表面获得最大硬度,宽度方向孔壁亚表层获得最大硬度,说明孔壁不同部位经受循环塑性应力影响程度不同,宽度方向孔壁发生应变硬化后循环软化成为薄弱区域;孔壁不同部位获得不同的切向残余应力场分布,长度方向孔壁表面获得最大残余压应力,宽度方向孔壁亚表层获得最大残余压应力,应力集中效应最强的宽度方向孔壁表面成为薄弱区域。     

Microstructure characterization and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy

The microstructure, microhardness and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy were experimentally investigated. Optical metallography and high-resolution hardness traverses were utilized to characterize the weld nugget, heat affected zone and base metal. The AA6111 spot welds displayed a softer nugget and hardened heat affected zone, compared with the base metal. The through-thickness hardness of the base metal sheet was not constant and had to be carefully considered to determine the effect of welding on material properties. Quasi-static lap-shear tensile tests were used to determine the failure load and failure mode. All tensile specimens failed through the interfacial fracture. This failure mode is consistent with the observed reduced hardness in the weld nugget.     

Effect of PTFE Addition on the Properties of Electroless Ni-Cu-P-PTFE Deposits

采用化学镀的方法,调整化学镀工艺参数,在低碳钢表面获得了PTFE含量不同的Ni-Cu-P-PTFE镀层,研究了PTFE粒子对Ni-Cu-P-PTFE镀层表面形貌、相、显微硬度、结合强度以及摩擦等性能的影响。结果表明,Ni-Cu-P-PTFE镀层的沉积速度随着PTFE浓度的增加而升高。进一步的实验结果表明,由于PTFE颗粒自身的疏松结构和软质特性,PTFE颗粒在镀层中的共沉积会引起Ni-Cu-P-PTFE镀层的显微硬度下降。同时Ni-Cu-P-PTFE镀层的结合强度会随着PTFE浓度的增加而减小。此外,PTFE的添加会使Ni-Cu-P-PTFE镀层的摩擦系数降低,这些结果与PTFE粒子在Ni-Cu-P-PTFE镀层中的含量成反比,而与镀液中PTFE粒子的浓度没有良好的对应关系。     

形变热处理对烧结Cu-Au合金性能与微观组织的影响(英文)

研究Cu-4%Au合金的硬度、显微硬度、导电性和微观组织在形变热处理过程中的变化。在加工硬化后,再对轧制合金在60～350°C温度下退火。由于退火硬化效应,合金的强度增大。结果表明:Cu-Au合金性能在两个阶段都得到改善;合金进行变形量为40%的热轧后,在260°C退火能得到最佳的综合性能。合金的微观组织也在形变热处理过程中发生显著变化。     

Microstructure,adhesion, and tribological properties of conventional plasma-sprayed coatings on steel substrate

A variety of metallic and oxide coatings were deposited under various conditions on 1020 mild steel substrate by conventional plasma spraying. The coating thickness, microhardness, cohesion and adhesion failure loads, friction coefficient, and abrasive wear resistance were evaluated. The coatings were classified as follows, in order of decreasing microhardness and wear resistance: alumina, chromia, 316 stainless steel, Ni-5% Al, elemental aluminum and aluminum-polyester. Wear resistance increased with increasing microhardness and decreasing friction coefficient. The microhardness and wear resistance of high-velocity oxy-fuel (HVOF) diamond jet (DJ)-sprayed aluminum were found to be superior to those of plasma-sprayed aluminum. Plasma or flame-sprayed metallic coatings adhered well to the substrate. The cohesion, adhesion, microhardness, and wear resistance of alumina coatings exceeded those of equally thick chromia coatings.     

Analysis of chemical macroheterogeneity in the vicinity of the fusion boundary in fusion welding

Research results of the supersonic powder surfacing of the high alloys on the surfaces of tube components of steam generating units with boiling bed are covered.