用掺碳活化烧结技术制取碳化硼材料

研究了 3种烧结活化剂 (葡萄糖、酚醛树脂和硬脂酸 )和不同的掺碳量对碳化硼烧结的影响。发现活化剂葡萄糖优于其它两种活化剂 ,以葡萄糖为活化剂 ,掺碳 3%,在 2 2 70℃氢气中常压烧结 1h获得的碳化硼材料密度为 2 .0 6 g/cm3 (相对密度 82 %) ,这一密度高于文献中报道的采用相同粒度粉末制得的结果。     

Boron carbide coating by electromagnetically accelerated plasma spraying

A new system of electromagnetically accelerated plasma spraying (EMAPS) consisting of a pulsed high-current arc-plasma gun and a large flow rate pulsed powder injector has been developed to synthesize a hard and dense coating of boron carbide (B₄C) with a high adhesion. The plasma gun with a co-axial cylindrical electrode configuration generates electromagnetically accelerated arc plasma with a typical velocity and maximum pressure of 1.5–3.0 km/s and 1 MPa, respectively, by discharging a pulsed high current of about 100 kA in peak and about 300 μsec of duration. The heating and accelerating of source powder are accomplished by injecting it into the inter-electrode space of the gun prior to the plasma generation using a newly developed pulsed powder injector that enables a gram of powder to be injected within 1 ms with precisely controlled time delay. With this system, hard B₄C coatings with a high adhesion and crystallinity were successfully formed on mirror-polished stainless (SUS304) substrates without a binder.     

Tool life increase of coated carbide tools by micro blasting

In today’s production engineering nearly every cutting tool is coated. Since using the technology of coating different process chains for reconditioning have been developed. The last innovation is micro blasted coatings, which is the main topic of this paper. Concerning this topic influences on tool life have been investigated. Investigations on the tool life especially of hobbing tools were made thereby and coherences between coating bond, roughness and other attributes were discovered. The investigations were made with an aluminum oxide and a zirconium oxide as blasting abrasives and a variation of the blasting parameters pressure and period. The final result is an optimization of tool wear behavior by micro blasting of the coating.     

Advances in grinding tools and abrasives

Because of their many applications, including automotive, aeronautics, optics, and so forth, demand for grinding tools sees unabated growth. But the energy and resource intensive nature of their manufacture leads to questions of sustainability. This paper details how recent developments in basic tool technology (structure, binder, abrasives) is increasing tool and abrasive resilience while reducing production inputs. The advent of smart grinding tools involving aspects of surface engineering, process hybridization, and process monitoring is also discussed. The paper concludes with an outlook of further energy savings, tool recycling and uses of additive manufacturing with the aim of achieving long-term sustainability.     

微晶氧化铝磨料的特性及制造

主要论述了微晶氧化铝磨料的概念、特性、在磨料行业的特殊地位，微晶氧化铝磨料的生产工艺，并简要介绍了世界上微晶氧化铝磨料的状况，以及微晶氧化铝磨料在中国的现状。     

Boron carbide B4C ceramics with enhanced physico-mechanical properties sintered from multimodal powder of plasma dynamic synthesis

Boron carbide B₄C as one of the hardest materials known is of a great scientific interest for years due to a unique combination of different useful properties. The ceramics on its basis has many prospective applications. However, the widespread usage of this ceramics is limited due to the relatively low fracture toughness as well as the poor sinterability. This work shows the possibility to obtain the ceramics with enhanced physico-mechanical properties based on the powdered boron carbide B₄C prepared by a plasma dynamic method. The key features of this powdered material are a single-crystalline particle structure and their multimodal distribution from several nanometers to several micrometers that is confirmed by the results of both scanning and transmission electron microscopy. Sintering the ceramics based on the as-prepared B₄C powder by SPS technology at the temperature of 1950 °C, pressure of 60 MPa and time exposure of 5 min allows not only achieving the expected values of ceramics density (~99% relative to the theoretical one) but also the high hardness (~37 GPa) and fracture toughness (6.7 ± 0.3 MPa·m^1/2).     

碳化硅磨料在陶瓷磨具中氧化性能的研究

碳化硅磨料在陶瓷磨具中的氧化性能对碳化硅细粒度陶瓷磨具的黑心有直接的影响，也是行业一直关注的问题；本文通过试验、结合化学动力学计算和扫描电镜分析，对碳化硅磨料在陶瓷磨具中的氧化性能进行了初步的研究。试验的计算结果表明：碳化硅磨料在现行的烧成制度下，氧化反应是不可避免的，氧化产物SiO2也不会在SiC磨料表面形成致密保护层；碳化硅磨具产生黑心原因关键在于陶瓷结合剂的性质。陶瓷结合剂的完全烧结温度若略高于烧成温度或能始终保持结合剂的适当开口气孔率，就可能避免产品黑心的产生。     

钢轨打磨技术及磨具研究进展

河南工业大学超硬材料与磨料磨具精密加工技术团队,始建于1989年,2014年入选河南省超精密加工技术创新团队,团队现有科研人员35人(包括17名教授、17名副教授,其中博士25名)。主要研究方向为:高温树脂金刚石/CBN磨具制备技术,高精密柔软金刚石涂附磨具制备技术,低温陶瓷结合剂金刚石/CBN磨具制备技术,磨料磨具磨削基础理论研究、PCD/PCBN复合片制备技术以及金属基超硬磨具的研究等。团队在高铁轨道、智能手机、汽车关键零部件、飞机发动机叶片、高精度轴承、刀具刃具、单晶硅/多晶硅、工程陶瓷、微晶玻璃、石材、高档家具等的精密研磨抛光方面获得了一批原创成果,并已广泛应用。团队在国内外学术刊物上发表论文300余篇,出版超硬材料和磨料磨具专业教材及著作21部;承担国家重大专项、省部级重大重点项目等40余项,获得省部级科技进步奖14项;获得国家发明专利46项,其成果直接转让经费1500余万元,创造直接经济效益20亿元。     

Fine finishing of internal surfaces using elastic abrasives

The paper describes a simple and innovative approach of using elastic abrasives for generating ultra fine finish on internal surfaces of tubular specimens. Elastic abrasive is a unique concept of using abrasive embedded elastomeric balls having the special capability to deform in conformity to work surface and thereby imparting a very fine refinement of its profile without altering the form. The mechanism of material removal in the proposed methodology is analysed using a mathematical model and its validation was done using a systematic experimentation procedure. Response surface methodology using central composite design is applied for the experimental study to investigate the effect of axial pressure, abrasive grain size and longitudinal stroke velocity of elastic abrasives on the surface finish. The process discussed in this paper is a simple and cost effective option to produce micro/nano-finish on the internal surfaces of a wide range of industrial components including hollow specimens, high aspect ratio bores and sleeves.     

超微晶陶瓷氧化铝磨料的研究

本文首先分析了传统刚玉磨料和超微晶陶瓷氧化铝磨料的特点。以A l2O3.H2O和HNO3为原料、Zn(NO3)2溶液为凝胶改良剂、超细Fe2O3为引晶剂、采用溶胶-凝胶工艺制备了超微晶陶瓷氧化铝磨料。对磨料的密度、硬度、韧性及磨削性能进行了测定。用正交实验考察了pH值、引晶剂、凝胶改良剂量等因素对磨料性能的影响。结果表明:各因素的影响顺序为引晶剂Fe2O3%量>酸度pH值>凝胶剂量。引晶剂Fe2O3%量不同,制得的磨料各项性能差别较大,添加量约为0.50%时、制得的磨料具有较佳的性能,磨料的密度为3.91g/mL、显微硬度为236MPa、磨削性能为传统刚玉的3.5倍。磨料性能可以和进口SG磨料相媲美。SEM电镜结果表明:该种磨料的晶粒度比较均匀,颗粒度较小,颗粒间不存在裂痕,样品的粒度在200-400nm。