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Plasma carburization at two different methane-to-argon gas ratios (5:5 and 6:5) was carried out on the cast TiAI based alloy of Ti-46.5Al-2.5V-1Cr (mole fraction, %) in order to enhance its wear resistance. The results show that after carburization under both carburizing atmospheres, Ti2AlC and TiC are the main carbides in the carburized layer and the value of surface hardness reaches more than HK 822, but for the carburized TiA; treated at CH4:Ar of 5-5, the surface carbon concentration is higher and the carburized depth is slightly thicker than that of alloy carburized at CH4:Ar of 6:5. The result of the ball-on-disk test against hardening-steel counter bodies shows that the wear resistance of the TiAl based alloy carburized under two different carburizing atmospheres is improved compared with non-carburized TiAl. The tribological property is related to the carbon content, and the carburized layer obtained at CH4:Ar of 5:5 possesses a stable friction coefficient, lower volume loss or wear rate and narrow wear scar, The characteristic of the carburized layer was examined by using optical microscopy, glow discharge spectrum and micro-hardness tester. 相似文献
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TC4 表面等离子 Ni 改性层摩擦磨损研究 总被引:3,自引:3,他引:0
目的研究TC4表面等离子Ni改性层摩擦磨损情况,以提高航空用钛合金的使用寿命。方法以近等原子比Ti Ni二元合金作为源极靶材,利用等离子表面合金化技术在TC4表面制备Ni改性层,考察合金层的组织、成分、相结构以及硬度分布,分析Ni改性层和基体的摩擦学性能。结果 Ni改性层主要由Ti2Ni,Ti Ni,Ti等相组成,Ni原子数分数最高为18%;表面硬度高达625HV;改性后的摩擦系数与基体相近,磨痕宽度是基材的1/3。结论 TC4表面等离子Ni改性层耐磨性增加。 相似文献
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一、引言
在建设服务型政府的理念下,公共管理部门要建设成为服务型部门。作为承担公共管理职能的法定计量技术机构,为了向服务型机构转变要不断提高公共服务形象、提升政府能力,绩效评估问题的研究和引入能为这些改变带来积极的作用。 相似文献
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ISO/IEC 17025:2017 《检测和校准实验室能力的通用要求》对实验室提出新的更规范更科学的要求,明确实验室活动范围不包括持续从外部获得的活动,增加并明确符合性声明的判定规则、新增客户要求的偏离的规定。文章在总结这些变化的基础上,结合应用和实践,对校准实验室实施合同评审活动进行风险点分析并提出相应措施,为校准实验室合同评审工作提供参考。 相似文献
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