超音速火焰喷涂Cr3C2-NiCr涂层在NaOH 溶液中的腐蚀及冲蚀腐蚀磨损性能

目的 分析超音速火焰喷涂制备的Cr3C2-NiCr涂层在碱性环境中的腐蚀及冲蚀腐蚀磨损性能,揭示涂层腐蚀及冲蚀腐蚀磨损失效机制。方法 利用超音速火焰喷涂技术在45#钢表面制备Cr3C2-NiCr金属陶瓷涂层,采用光学显微镜、显微硬度仪、碱性环境腐蚀性能试验台、电化学分析仪、冲蚀腐蚀磨损试验机、电子天平、扫描电子显微镜,分别对组织结构、显微硬度、碱性环境下耐蚀性能、耐冲蚀腐蚀磨损性能、冲蚀腐蚀磨损损失质量及表面形貌进行测试。结果 Cr3C2-NiCr涂层呈典型层状结构,内部随机分布着孔隙及氧化物,涂层孔隙率及显微硬度平均值分别为1.3%和817HV0.1。在pH=11的NaOH溶液中,涂层的电化学腐蚀电位为-0.38 V,腐蚀反应生成的氧化物可有效阻止腐蚀继续进行,长期浸泡过程中,腐蚀介质通过裂纹或穿透性孔隙渗入涂层内部直至基体表面,并发生腐蚀反应,形成的腐蚀产物逐渐累积并排出至涂层表面,最终形成体积较大且呈团絮状的腐蚀产物。在碱性腐蚀环境下,腐蚀介质加剧冲蚀磨损中的材料消耗。相同条件下,涂层腐蚀冲蚀磨损损失质量明显小于基体材料,涂层的冲蚀腐蚀磨损失效机制主要有腐蚀产物脱落、硬质颗粒剥落、粘结相磨耗、缺陷处因疲劳裂纹整体脱落。结论 在碱性环境中,Cr3C2-NiCr涂层具有较强的耐腐蚀性能,腐蚀介质能加快涂层冲蚀磨损进程,磨损后表面为非光滑表面,使涂层具有较优的抗冲蚀磨损性能,故Cr3C2-NiCr涂层可显著改善基体表面的综合使用性能。     

Microstructure and wear resistance of Fe-based and Co-based coating of AISI H13

Fe-based and Co-based cladding layers were prepared on the surface of AISI H13 hot die steel by laser cladding technology. The microstructure, hardness and abrasion resistance of the two cladding layers were studied by means of optical microscope, scanning electron microscope, rockwell hardness tester, and high temperature friction and wear tester. Also, the red hardness of the cladding layers was measured, after holding the layers at 600 ℃ for 1 hour by muffle furnace and repeated 4 times. The rockwell hardness values of the substrate, the Fe-based and the Co-based alloy coating measured were HRC 47, HRC 52 and HRC 48, respectively. The red hardness values of the substrate and the Fe-based cladding layer were decreased, while that of the Co-based cladding layer was increased. The Co-based cladding layer has the minimal wear loss weight and friction coefficient among them. The wear mechanisms of the substrate, the Fe-based layer and the Cobased layer attribute mainly to abrasive wear, adhesion wear, and both of them, respectively.     

基于HyperWorks的特种车辆摇臂有限元分析

以某型特种车辆摇臂为研究对象,根据摇臂相邻部件系统配合关系确定分析边界,利用Pro/E建立摇臂三维模型,导入HyperWorks软件中添加约束和载荷,利用有限元分析得到摇臂应力、应变结果。分析发现摇臂与轮系配合部位有应力集中现象,如果直接生产制造会有安全风险。依据分析结果对摇臂进行结构优化,对改进后的模型再次进行分析,平衡肘最大应力从752MPa降至516MPa,与轮系配合部位应力降至432MPa,满足设计需求。利用软件分析工具指导产品设计,提前发现并解决应力集中问题,降低新产品研发风险。     

渗氮温度对40Cr钢QPQ组织与性能的影响

采用光学显微镜(OM)对不同渗氮温度QPQ处理的40Cr钢表面渗氮层显微组织进行观察分析,同时进行维氏硬度试验与销盘摩擦磨损试验,获得渗氮层硬度梯度与磨损失重,并观察分析了磨损表面SEM形貌。结果表明,经不同渗氮温度的QPQ处理后,40Cr钢表面均形成了由氧化膜层、化合物层与扩散层构成的表面渗氮层。但随渗氮温度的升高,其渗氮层厚度呈先增加后减小的变化趋势,4种渗氮温度(580、600、620、640 ℃)下样品有效渗层深度分别为0.14、0.20、0.29、0.26 mm。随渗氮温度的升高,磨损量呈先减小后增大的趋势,在620 ℃下达到最低值。4种渗氮温度下磨损形式均以磨粒磨损与粘着磨损为主,但随着渗氮温度升高带来渗氮层厚度与硬度的变化,磨损程度呈现逐渐减轻的趋势。     

H13钢激光相变硬化的组织与性能试验研究

为提高H13热锻模具的耐磨性能和耐腐蚀性能,利用激光相变硬化技术对H13钢进行处理,采用XRD衍射仪、光学显微镜、扫描电镜、显微硬度仪、电化学工作站及高温摩擦磨损试验机对其相结构、显微硬度、耐腐蚀性及耐高温磨损性能进行测试。硬化层由针状马氏体、板条马氏体和碳化物组成,硬化深度为0.71 mm,显微硬度约为750 HV0.3。在脱模剂溶液中,硬化层的自腐蚀电流密度比基材小一个数量级。硬化层高温磨损的质量为基材的7%,磨损机理以黏着磨损为主,同时伴有磨粒磨损和氧化磨损。     

Mathematical modeling on multi-stage series crushing ratio distribution based on fuzzy physical programming

Double-layer, multi-roller plate crusher is a new device, that uses a multi-stage series crushing style to break particles, with the crushing ratio distribution directly influencing the machine’s performance. Three crushing ratios of 2.25, 2.15 and 2.01, used for fuzzy physical programming, were determined. The comparison of the optimized result between the double-layer multi-roller plate crusher and a high pressure roll grinder showed that the double-layer multi-roller plate crusher had a better performance, reducing crushing force and wear.     

Research on the system configuration and energy control strategy for parallel hydraulic hybrid loader

Aimed at the frequent starts/stops operation characteristics of the loader, an energy saving scheme with parallel hydraulic hybrid system is proposed to regenerate and reuse the braking energy normally lost in a conventional loader. Hydraulic hybrid system is designed and sized to capture braking energy from normal–moderate braking operating modes while ensures hybrid system working in higher efficiency region. According to the higher power density characteristic of hydraulic hybrid system, the regenerative braking strategy and energy reuse strategy are designed to coordinate all the powertrain components in an optimal manner while satisfying performance constraints of loader. Energy controller using logic threshold approach is built up to control the dynamic transitions among the various operation modes. Simulation and experimental results show the parallel hydraulic hybrid loader (PHHL) effectively recovered and reused the braking energy, improved the working performance of loader and effectively reduced the fuel consumption.     

高温超声冲击处理Q345钢焊接接头的疲劳性能

利用自行研制的超声冲击处理装置,对Q345钢对接接头焊趾区分别进行了室温(20℃),250,350及450℃下的高温超声冲击处理,并对处理后接头的疲劳性能进行了研究.结果表明,在应力比R=0.1的条件下,室温及高温超声冲击处理均能有效改善Q345钢对接接头的疲劳性能,且250℃超声冲击处理接头的疲劳性能与原始焊态相比,改善程度最大,高达99.41%.此外,在残余应力和应力集中因素的影响下,焊接接头疲劳强度的改善程度随超声冲击温度的升高呈先上升后下降的趋势.     

Failure of a swing pinion shaft of a dragline

The causes of failure of a swing pinion shaft of a coal handling dragline have been investigated in the present work. Along with the failed shaft, a small piece of material from the tooth of another shaft that rendered design life in service has also been analyzed. The chemical composition and general heat treatment of the shafts were as per recommendation. The microstructure of both the shafts was tempered bainite, which is usual for such pinion shafts. The mechanical properties met the requirement for such applications. The investigation included metallography, microscopy (SEM), hardness and fractography. Analysis revealed fatigue cracks initiated at a number of places along the length of the tooth, and grew to a considerable depth. Improper surface hardening of the pinion teeth is believed to have rendered the teeth susceptible to bending fatigue failure. Other factors like lubrication and impact loads in the tooth roots might have aggravated the failure.     

圆锥破碎机一套多冲程偏心套组件的设计

为了减少圆锥破碎机零部件数量和实现"一套多冲程"的功能,提出一种优化设计偏心套组件关键参数的方法。采用坐标转换的方法建立圆锥破碎机偏心套组件中轴线夹角、相对转角和偏心量与冲程的关系模型,通过优化计算和实例获得某一型号圆锥破碎机的偏心套组件的关键参数,结合三维模型分析,证明优化获得的结果能满足设计需要,对于单缸圆锥破碎机偏心套组件的设计具有一定的参考意义。