原位自生钢基复合材料耐磨性能的研究

用铸造的方法制备了原位自生复合碳化物[(Ti,W,Cr,V,Nb)C]增强钢基复合材料,并对该复合材料的磨粒磨损性能及磨损机理进行了研究。结果表明,采用该方法制备的钢基自生复合材料中,自生碳化物颗粒细小、圆整、且分布均匀,碳化物颗粒增强相体积分数达到42.8%;原位自生钢基复合材料的耐磨性能优良。在磨粒磨损条件下,其磨损机制主要是显微切削、颗粒脱落和脆性剥落;稀土和合金元素能够提高原位自生钢基复合材料的耐磨性能。     

A359-Zr(CO3)2体系反应合成复合材料的组织及润滑磨损性哪

研究了新型反应体系A359-Zr（CO3）2熔体反应法制备的（Al3Zr＋Al2O3）p／A359复合材料边界油润滑条件下的滑动磨损性能。结果表明，由于颗粒的支撑减磨作用，复合材料的磨损量随载荷的增大和时间的延长均远小于基体材料，当载荷为1176N时体积分数为12％的复合材料磨损量为4．9mg，而基体材料的磨损量为27．5mg，复合材料比基体材料耐磨性提高了6倍；由磨损表面SEN观察表明：基体A359合金存在严重粘着和变形，表现为粘着磨损和剥层磨损，复合材料的磨损类型表现为磨粒磨损。     

Effects of temperature and current density on the surface hardness and tribological properties of Ti-6Al-4V alloy by molten salt carburization

Surface hardening of Ti-6Al-4V alloy was achieved by carburization in a molten salt bath containing BaCO₃ as the carbon-yielding agent with electrolysis within the temperature range 790–930°C. The hardness of the total carburizing layer (TCD) is influenced by the bath temperature, the applied current density and the carburizing period. The major hardening effect is considered to be the formation of a solid solution of carbon in -Ti. The oxide film wrapping at the outermost surface of cathodically charged specimens, identified to be mainly BaTiO₃, was formed irrespective of the bath temperature during the quenching process and has no effect on the surface hardening. The optimal carburizing parameters obtained in this study for surface hardening are carburizing at 930±10°C (bath temperature) and 0.3 A/Cm² (applied current density) for 90 min (carburizing period), while those for tribological properties improvement are carburizing at 860±5°C and 0.3 A/Cm² for 90 min.     

Bio-mimetic surface structuring of coating for tribological applications

A novel multilayered coating was developed for applications associated with friction reduction and wear resistance improvement. The nano-engineered coating integrates a soft lubricating layer, consisting of MoS₂-PTFE, onto hard load-supporting layers, with controlled surface morphology (roughness and patterning) of cBN-TiN. The coating was synthesized by sequential procedures including electrostatic spray deposition of cBN particles with different average particle sizes, chemical vapor deposition of TiN, deposition of nano- and micro-sized MoS₂ dispersed in PTFE, and curing. The effect of cBN particle size (with different combinations of particle size) and deposition parameters (specifically electrical voltage) on the cBN-TiN surface morphology were studied experimentally and optimized. SEM characterization of the as-synthesized cBN-TiN coating shows surface features similar to that of colocasia esculenta, with alternating nano- and micro-sized domes and “pockets”; the MoS₂-PTFE top layer has MoS₂ particles retained in the pockets by a basket structure formed during PTFE curing. Tribological and scratch tests were carried out for the as-prepared cBN-TiN and cBN-TiN/MoS₂-PTFE multilayered coatings. Sliding test results demonstrate significantly lower friction coefficient for the multilayered coating, showing that the unique integration of soft lubricating layer and biomimetically structured hard layer can effectively improve tribological performance. It is suggested that lubrication at the frictional contacts was realized by continuous release of the lubricants, MoS₂ and PTFE, from the pockets.     

Microstructure and tribological properties of Cuss-toughened Cr–Cu–Si metal silicide alloys

Wear resistant Cr–Cu–Si metal silicide alloys with different Cu contents were fabricated by the laser melting process. The Cr–Cu–Si alloys have a similar microstructure consisting of the Cr₅Si₃/CrSi dual-phase primary dendrites and the interdendritic Cu-based solid solution (Cu_ss). The Cu content has no effect on the phase constitutions of the alloys. The Cr₅Si₃/CrSi dendrite volume fraction and hardness of the Cr–Cu–Si alloys decrease with the increasing Cu content. Wear test results indicate that all the Cu_ss-toughened metal silicide alloys have excellent wear resistance and low coefficient of friction. Wear resistance increases and friction coefficient decreases with the decreasing Cu content.     

高强度铸造铝合金凝固过程中的元素偏析

通过液淬的方法，研究Al-4.5Cu合金及添加Si,Mn,Ni,Zr元素后合金的凝固过程及溶质分布。结果表明，将Si,Mn,Ni,Zr元素的加入，都能使Al-Cu合金的结晶温度间隔不同程度地减少，其中Al4.5Cu3Si的结晶温度间隔最小，Cu的分布,特点是：晶界高于晶内，一次晶界高于二次晶界”，并随着温度的降低Cu向晶界偏析的趋势加剧，Ni的分布，晶界高于晶内，Mn的分布，晶界高于晶内，但差别不大，Zr在晶界与枝晶间的偏析处的含量较高。     

Characterization of in situ synthesized TiC particle reinforced Fe-based composite coatings produced by multi-pass overlapping GTAW melting process

In this paper, in situ synthesized TiC particles reinforced Fe-based surface composite coatings by multi-pass overlapping gas tungsten arc welding (GTAW) melting process employing a proper amount of graphite and ferrotitanium (FeTi) on AISI 1020 steel substrate was produced. The microstructure and wear properties of the composite coatings were investigated by means of an electron microprobe microanalysis (EPMA), X-ray diffractometer and wear tester. The results showed that the multi-pass overlapping GTAW melting surface composite coatings can be obtained under suitable welding parameters, and no crack and porosity are found in the tracks. The X-ray and EPMA results confirm that TiC particles can be formed via reaction of FeTi and graphite during multi-pass overlapping GTAW melting process. TiC particles present cubic and dendrite shape in the non-overlapping zone. It is found that there occurred TiC particles coarsening at the overlap regions, which can lead to detrimental effects on the hardness and wear performance. Composite coatings give a high hardness and excellent wear resistance; and the wear friction coefficient of the coating is less than that of the 1020 steel. As a result, multi-pass overlapping GTAW melting process can be used effectively for producing surface composite coatings with a pre-placed powder to improve wear resistance of the AISI 1020 steel.     

An Investigation of Grinding with Electroplated CBN Wheels

Grinding of hardened bearing steel with electroplated CBN wheels was Investigated with particular attention to how the wear of the abrasive grains affects the wheel topography and grinding performance during the wheel ire. Power, surface roughness, and wheel topography data were obtained throughout the wheel life for internal cylindrical grinding. Dulling of CBN gratis by attrition was found to cause an increase in the grinding power, but the degree of dulling was restricted mainly by grain fracture and also by grain pullout. Grain fracture and pullout had a much smaller effect on the progressive increase in active grain density, which caused the surface roughness to progressively decrease. Wheel failure tended to occur by stripping of the abrasive layer when the radial wear reached about 70% - 60% of the grain dimension     

无氰电刷镀金技术在航天工业中的应用

应用FJY-18无氰电刷镀金技术制得的金镀层具有孔隙率低、色泽金黄、光亮、结合力好,镀厚能力大于20μm,显微硬度HV=130～150,施工温度范围宽、无毒等特点,该技术已用于航天工业中某一关键部件的表面减磨密封镀金.     

不同载荷下CuZnAl合金干滑动磨损性能研究

对CuZnAl（RE）形状记忆合金采用不同热处理工艺后,进行了干滑动磨损试验.在不同相变温度、不同载荷、不同磨损时间的条件下,做了CuZnAl（RE）形状记忆合金的干磨损试验,并与ZQSn5-5-5和ZQAl9-4做了对比,用电子扫描显微镜和X衍射仪对磨损表面和磨屑相组成进行了观察和检测.试验结果表明,晶粒细化与锻打能提高合金的耐磨性,合金的M相比β相耐磨,两级时效处理的合金耐磨性能优于分级淬火处理的合金.CuZnAL（RE）形状记忆合金的耐磨性优于ZQSn5-5-5和ZQAl9-4.CuZnAl（RE）形状记忆合金磨损机制主要为粘着磨损、剥离磨损和磨粒磨损.