Advanced Materials Research Vols. 126-128

Abstract: In order to understand the friction characteristics of hot-pressing bit matrix and granite under dry sliding conditions, the influence law of hardness and diamond concentration to the friction coefficient was analyzed and discussed with the data of friction coefficient and torque under different conditions. Three groups of hot-pressing matrix samples of different hardness and three groups of hot-pressing matrix samples with different diamond concentration were chosen. The friction and wear tests were carried out between hot-pressing matrix samples and granite samples. The results showed that the friction torque and coefficient firstly increased, and then decreased with the increase of hardness in dry friction experiments between granite sample and matrix sample without diamond. Compared with data from matrix sample without diamond, the friction torque and friction coefficient decreased significantly when test was carried between granite sample and impregnated diamond matrix sample. The friction torque and coefficient increased with the increase of diamond concentration.

Abstract: In this paper, the effects of the surface asperity wavelength, reduction and lubrication (friction) on the surface roughness transformation of the oxide scale have been studied. The simulation results show that the oxide scale surface roughness decreases with an increase of the average asperity wavelength and reduction. The initial surface roughness affects the decrease rate of surface roughness when the reduction increases. The surface roughness of the oxide scale and steel is quite close when the rolling with lubrication and both of them are reduced with reduction, and the surface roughness of the oxide scale is reduced less comparing with that of without lubrication case. The calculated roughness is close to the measured data.

Abstract: The monolayer brazed diamond tools have recently been used increasingly in hard-brittle materials grinding because of their excellent grinding performances as long tool life, high material removal rate and large inter-grit chip space, etc. However, they possess an inherent shortcoming of the high roughness of the grinding surface. This work is an attempt to reduce the over-protruded grits of the monolayer brazed diamond wheel so that precision grinding operations can be executed effectively. In this investigation, the monolayer brazed diamond wheels with regular distribution pattern of grit have been dressed by a special conditioning process and used in precision grinding experiments on Li-Ti ferrite. The outcome of this attempt appeared highly encouraging. A substantial improvement of the ground surface roughness could be achieved with the dressed monolayer brazed diamond wheels.

Abstract: The grinding should be improved to be the skill-free process executed based on the quantified criteria. In this study, the evaluation methods are applied to evaluate the dressing process to clarify how the dressing changes the cutting-edge distribution. From the results, the following facts have been clarified: There is the critical value of the depth of cut for suppressing the release of grain. The spark-out in dressing releases grains damaged by collision with dresser, and then, it also increases the cutting-edge density.

Abstract: This paper reports a systematic investigation of a nozzle-type ELID grinding characteristics of cemented carbides. Two groups of experimental scheme were carried on by using fine grain cast iron diamond wheel and nozzle-type ELID grinding apparatus. The grinding forces were measured by a dynamometer and the ground surfaces were characterized using scanning electron microscopy (SEM) and atomic force microscope (AFM). The influences of electrolytic and grinding parameters on grinding force were discussed. The material removal mode and micro-morphology characteristics were also analyzed.

Abstract: Due to the continual improvement of CMP technologies, and the need for polishing delicate wafers at high speed, graphite impregnated pads (GiP) dressed by brazed organic dia mond disks (BODD) can double the throughput of wafer-pass at the reduced cost of ownership (CoO). The increased polishing rate is due to the act of nano graphite particles that absorb slurry. The nano graphite particles coated with chemical and abrasive can achieve high removal rate without causing scratches on the wafer. In addition, nano graphite particles do not stick to wafer surfaces, so they can be cleaned easily. BODD can uniquely dress GiP to create slurry channels so the pore free pad is not bottlenecked by slurry supply. This paper also demonstrated the low stress polishing by applying ultrasound during the CMP process.

Abstract: Titanium is a metal material which has many excellent properties; it has been widely used in many fields. In this paper, plane abrasive machining is carried out for Titanium plate. The surface roughness and morphology of Ti-plate is compared after fixed and loose abrasive machining. The experiment proved that the drop magnitude of Ra in loose abrasives machining is great larger than that in fixed abrasive when grit size is nearly equal, and the improvement of surface defect such as some directional marks, deep scratch and bits in loose abrasives machining is rapider and quicker than that in fixed abrasives during same machining time. The results of experiments indicts that loose abrasive machining is better than fixed abrasive in reducing surface roughness and improving surface morphology, since the higher density of active abrasives and machining force uniformity.

Abstract: This research studies an effective polishing process to elevate the surface precision and homogeneity by improving the polishing trajectory of magnetic brush. The moment of magnetic brush is a key influence factor on finishing characteristics, but in conventional plane magnetic abrasive Polishing process, the movements of magnetic brush is relatively simple. In this paper a polishing process using the complex polishing trajectory of magnetic brush has been modified and studied by use of newly designed experiment device. The linear movement of workpiece, the rotation and revolution or movement in XY coordinate plane of magnetic brush can be realized by this device. In comparison with conventional method, variation regularity about surface roughness and the material removal are been studied. According to experimental results for polishing trajectory of magnetic brush, finishing characteristics was clarified. The results show that studies on polishing trajectory of magnetic brush are more valuable and the experimental researches are consistent with theoretical analysis. In addition, the accuracy of plane magnetic abrasive finishing can be elevated in terms of the reasonable planning for polishing trajectory of magnetic brush.

Abstract: In order to reduce or eliminate the surface defects caused by abrasive grains and improve the efficiency of ultra-precision processing, the technique of semi-fixed machining has been proposed for machining advanced ceramics. A semi-fixed abrasive tool (SFAT) has been manufactured; it has performances of semi-fixed machining technique. This document demonstrates wear characteristics of SFAT through experiments of machining silicon wafer. It showed that wet status or dry status of SFAT has greatly influenced wear characteristics of SFAT. Wear characteristic of SFAT presented mostly blockage and little grain-off occurred in dry status; mostly grain-off and little blockage presented in wet status.