Teruko Kato

ELID grinding and tribological characteristics of TiAlN film

Abstract This paper presents the results of electrolytic in-process dressing (ELID) grinding experiments performed on TiAlN film and characterization of the tribological characteristics of the produced films. In advanced films coated by physical vapor deposition, such as CrN and TiAlN, the low surface roughness required for attaining superior tribological characteristics is difficult to attain by use of only a coating process. ELID of grinding wheels improves wheel performance, enabling the attainment of specular finishes on brittle materials, with surface roughness on the nanometer scale (4 to 6 nm). In the present study, high-quality TiAlN film surfaces were fabricated by the ELID technique, typically achieving a surface roughness of around Ra 0.0024 μm by employment of a SD#30,000 wheel. Scanning electron microscopy reveals that ELID improved the finish, as indicated by the shape of grinding marks. Chemical element analysis by an energy-dispersed x-ray diffraction system suggests that ELID grinding formed an oxide layer in the machined surface of TiAlN film. Therefore, in addition to the highly smooth surface, an oxide layer formed by ELID grinding imparts superior tribological properties to ELID-ground TiAlN film.

Evaluation of surface characteristics of ground CVD-SiC using cast iron bond diamond wheels

The precision and efficient machining of CVD-SiC ceramic to required quality has not been well established yet. In this paper, a comparative study was conducted to investigate the special aspects in grinding of CVD-SiC ceramic, with ELID method or rotary dressing method. The stability of surface roughness, effects of material properties and dressing methods on grinding results, effects of material properties and dressing methods on surface stress state, and microscopic analysis of ground CVD ceramics by both methods were well analyzed. In addition, a wheel-workpiece interaction model was proposed for the two dressing methods.

A comparative study: surface characteristics of CVD-SiC ground with cast iron bond diamond wheel

Efficient precision machining of CVD-SiC (chemical vapor deposited silicon carbide) reflection mirrors in extremely low surface roughness and high form accuracy is greatly demanded by advanced industrial fields. The existing lapping methods have a great difficulty in satisfying these demands. Some researchers proposed ductile mode grinding technology, but it inevitably required a very expensive grinding machine, and its grinding process with such fine abrasive wheel was usually unstable. Dr. H. Ohmori put forward a new idea of application of ELID-grinding to ultraprecision grinding of CVD-SiC mirrors. The method had a potential to solve the above problem. In this paper, the precision grinding of CVD-SiC was performed by two kinds of methods. One is the ELID grinding; the other is the ordinary grinding with the saw-like-abrasive-stone-dressed cast iron bond diamond wheel. A comparative study of surface characteristics of ground CVD-SiC has been carried out. The following conclusions have been drawn below. (1) The surface characteristics of wheels dressed by these two methods are different. (2) The surface roughness ground by ELID grinding was only slightly better than the one produced by the ordinary grinding method. (3) The microscopic characteristics of CVD-SiC ground by these two methods differed largely. (4) ELID grinding is greatly recommendable in precision grinding of hard-brittle materials on ordinary machines of low rigidity.

Estimation of Tribological Characteristics of Electrolyzed Oxide Layers on ELID-Grinding Wheel Surfaces

The purpose of this work is to investigate tribological characteristics of electrolyzed oxide layers on ELID-grinding wheel surfaces under dry and lubricated conditions. A pin on disk type wear apparatus is used with reciprocating lower disk specimen. Two kinds of carbon bond materials CR and CRB, and cast iron bonded materials SD are used for the disk specimen. The normal load is changed from 0.49 N to 4.9 N. It was found that when two kinds of carbon resin bonded materials are used for disk specimen, friction coefficient of electrolyzed layers has a higher value than that of without electrolyzed layer. Specific wear rate of CR with electrolyzed layer is from 2 to 11 times of the one without electrolyzed layer. Specific wear rate of CRB with electrolyzed layer is from 10 to 128 times of the one without electrolyzed layer. Specific wear rate of SD with electrolyzed layer is from 45 to 461 times of the one without electrolyzed layer.

Friction and Wear Properties of an ELID-Grinding Wheel based on CCD Microscope Observation

The friction and wear properties of an ELID-grinding wheel with an oxide layer were investigated by using a CCD microscope tribosystem under dry and lubricated conditions. When the #400 diamond wheel is used as a disk specimen, the friction coefficient is 0.23-0.58 under dry conditions, and 0.11-0.38 under lubricated conditions. When the #4000 diamond wheel is used, the friction coefficient is 0.16-0.76 under dry conditions, and 0.15-0.38 under lubricated conditions. The specific wear rate (ws) of the #400 or #4000 diamond wheel with an oxide layer has a higher value than that of a cast iron bond wheel under lubricated conditions, when the contact pressure is more than 0.6 MPa. Furthermore, the ws of the #400 or # 4000 diamond wheel with an oxide layer under lubricated conditions has comparatively higher value than that of the #400 or #4000 diamond wheel under dry conditions. If the grain size is large, it is effective to decrease the friction coefficient in order to increase the cutting ability of the diamond grain.

Study on Tribo-Fabrication in Polishing by Nano Diamond Colloid

Now that nano diamonds can be produced stably at low costs, there are growing needs to explore new areas of applications. This report discusses basic polishing experiments performed on nano diamonds to investigate their frictional and wear characteristics during polishing, and the results been obtained. The authors also propose a new terminology “tribo-fabrication” to mean an area of research on tribological phenomena seen with the interface of workpiece and tool surface in ultra-precision fabrication. These new term as well as the polishing characteristics of nano diamond are discussed.

Electrolytic in-process dressing grinding of sapphire with nanodiamond composite wheel

In this paper, nanodiamond (ND) was applied to a processing additives used in the manufacture to a wheel for grinding sapphire. Nanodiamond was produced by the detonation of trinitrotoluene explosives technique, and the tribological characteristics of ND solution were investigated. Sapphire was a difficult material to process with high quality, precision and efficiency. With the aim of reducing friction and friction heat between the wheel and sapphire surfaces, metal resin bonded diamond wheels (#2000, average grain size: 8 µm) containing ND with 0.2, 1.0, and 2.0 vol.% were produced. Appropriate machining parameters were selected for electrolytic in-process dressing (ELID)-grinding process (Ohmori and Nakagawa, 1990), and the grinding behaviour of sapphire was evaluated. In summary, an extremely smooth surface of sapphire wafer was fabricated by using the #2000 metal resin bonded diamond wheel containing 2.0 volume percent ND and a rotary in-feed grinder with ELID.