Fine finishing of tungsten alloy is required to improve the surface quality of molds and precision instruments. Nevertheless, it is difficult to obtain high-quality surfaces as a result of grain boundary steps attributed to differences in properties of two-phase microstructures. This paper presents a theoretical and experimental investigation on chemical mechanical polishing of W–Ni–Fe alloy. The mechanism of the boundary step generation is illustrated and a model of grain boundary step formation is proposed. The mechanism reveals the effects of mechanical and chemical actions in both surface roughness and material removal. The model was verified by the experiments and the results show that appropriately balancing the mechanical and chemical effects restrains the generation of boundary steps and leads to a fine surface quality with a high removal rate by citric acid-based slurry.

The importance to industry of non-contact bearings is growing rapidly as the demand for highspeed and high-precision manufacturing equipment increases. As a recently developed non-contact technology, near-field acoustic levitation (NFAL) has drawn much attention for the advantages it offers, including no requirement for an external pressurized air supply, its compact structure, and its ability to adapt to its environment. In this paper, the working mechanism of NFAL is introduced in detail and compared to all existing non-contact technologies to demonstrate its versatility and potential for practical applications in industry. The fundamental theory of NFAL, including gas film lubrication theory and acoustic radiation pressure theory is presented. Then, the current stateof- the-art of the design and development of squeeze film air bearings based on NFAL is reviewed. Finally, future trends and obstacles to more widespread use are discussed.

为有效解决金刚石刀具表面轮廓质量评价指标分散、无法进行全面系统测量的难题，基于原子力显微镜和超精密回转轴系，提出了实现前后刀面粗糙度、刃口锋利度和刃口微豁三个关键指标的集成测量方法。根据金刚石刀具表面轮廓质量的测量要求，以原子力显微镜扫描系统、气浮隔振平台、二维移动平台以及精密回转轴系为基础构建测量系统，精确测量了金刚石刀具刃口附近的表面微观形貌；采用基于MATLAB开发的专用测量软件对原始数据进行处理，得到金刚石刀具前后刀面粗糙度值、刃口锋利度值和刃口微豁范围；并对测量误差进行了分析，提出了控制要求。通过上述自主开发的测量仪器，可以高效、完整地描述金刚石刀具表面轮廓质量，能够实现nm级粗糙度、亚μm级锋利度以及μm级微豁的准确测量。