Norihiko Narutaki

High-speed machining of Inconel 718 with ceramic tools

Summary High speed machining for Inconel 718 was carried out with SiC whisker reinforced alumina, silicon nitride and TiC added alumina ceramic tools. In this test, not only the commercial available inserts, square type 120408 or button type 120400, but also specially designed cutting edges were tried. The SiC whisker tool showed the best performance in respect of notch wear at the cutting speed of under 300m/min. However, when the speed exceed -400m/min., the TiC added alumina ceramic tool showed the smallest wear compare to other tools. Specially designed cutting edge made the notch wear small.

Study on Machining of Titanium Alloys

Summary In this study, an experimental investigation to improve the machining efficiency of titanium alloys has been conducted. In machining titanium alloys, generally, the cutting tools wear off very rapidly because of the high cutting temperature resulted from the low thermal conductivity and density of the work material. In order to increase the tool life, it is necessary to suppress the cutting heat as much as possible. In this experiment, a natural diamond tool characterized by the highest thermal conductivity of all the tool materials available was utilized by applying abundant water-soluble coolant. It was found that the natural diamond tool exhibits an excellent cutting performance in machining titanium alloys, and the cutting speed could be increased up to 3.33 m/s when applying abundant coolant. In addition, the quality of surface machined with the natural diamond tool was found to be better than those with the other tools.

The formation of a protective oxide layer in machining resulphurized free-cutting steels and cast irons

Abstract The effect of a protective oxide layer on tool surfaces in machining resulphurized steels and cast irons has been studied. In the case of resulphurized steels a protective layer was formed on TiC-added carbide tools and alumina ceramic tools when cutting steels containing a high level of oxygen and proper contents of aluminium and silicon, and the layer suppressed the wear of these tools. A protective layer was also observed on silicon nitride ceramic tools when turning cast irons containing a high level of oxygen and a proper content of aluminium. The wear of the ceramic tool in cutting FeSi deoxidized resulphurized steels was serious, and in some cases the crater depth of the tool became larger than that of the carbide tool.

Machinability of pearlitic cast iron with Cubic Boron Nitride (CBN) cutting tools

In order to increase the accurate finishing productivity of pearlitic cast iron, face milling by CBN (Cubic Boron Nitride) cutting tools was studied. The main focus of the study is the machinability investigation of pearlitic cast iron with CBN cutting tools by studying the relationships among machining conditions such as feed rate, cutting speed as well as CBN cutting tool type, tool wear, workpiece surface quality, cutting forces, and cutting temperature. In addition, an emphasis is put on the effect of Al additive in pearlitic cast iron on its machinability and tool wear characteristics. High-speed milling experiments with CBN cutting tools were conducted on a vertical machining center under different machining conditions. The results obtained provide a useful understanding of milling performance by CBN cutting tools.

Cutting Performance and Wear Characteristics of an Alumina-Zirconia Ceramic Tool in High-speed Face Milling

Summary High speed face milling for plain carbon steel S45C was carried out with ceramic tools. Pure alumina. T/C added alumina, and Zirconia toughened alumina ceramic tools were mainly used. Among the tested ceramic tools, the zirconia toughened alumina ceramic tool! showed the largest crater wear resistance in high speed face billing. However, in turning the same steel, the crater wear resistance of the ceramic tool was almost the same degree as compared to the other ceramic tools. The superior wear resistance of the zirconia toughered alumina ceramic tool is based on its stability for the reaction to Fe0 at high temperature.

High Speed Machining: A Review from a Viewpoint of Chip Formation

This paper describes strong nonlinearity in log V-log L relationship, which is often found in machining of supperalloys, titanium alloys, hardened steels, cast irons, etc. The nonlinearity plays an important and favorable role in extension of life-span cutting distance at higher cutting speeds; that is, in a certain range of cutting speed, life-span cutting distance increases with cutting speed. Results of tool wear in a sliding test and cutting experiments, which showed the evidences of strong nonlinearity, were investigated and the mechanisms causing the nonlinearity were discussed.

Cutting performance of high purity alumina ceramic tools formed by a high-speed centrifugal compaction process

Abstract Using a high-speed centrifugal compaction process (centrifugal force: 1 × 104 −2 × 104 G) developed by the authors, a slip prepared from alumina powder with a purity of 99.99% and an average particle size of 0.22 μ m was compacted, and sintered at 1230 °C for 1.5 hours in the atmosphere. The sintered compact has superior mechanical properties, including a 3 - point bending strength of 1330 MPa and a Vickers hardness of 2100. The cutting performance of this alumina sintered compact was studied. The results show that tools manufactured using the subject high-speed centrifugal compaction process have relatively high wear resistance and fracture resistance as compared with commercially available high purity alumina ceramic tools.

Suppression of tool wear by using an inert gas in face milling

Abstract In order to reduce crater wear and thermal cracks of cutting tool in high speed face milling of plain carbon steels, an inert gas, which flowed through a spindle of a milling machine, was used. Nitrogen gas was supplied through spindle to the cutting edge so that the cutting edge would not be oxidized. The effects of the nitrogen gas on the tool failure were influenced by shape of the nozzle and velocity of the gas from the nozzle. Under the good conditions, crater wear of the carbide tool P10 was reduced by 50% compared to cutting in the air.

Machinability of BN Added Steels. Third Report. Machinability in Face Milling.

This paper deals with machinability of BN added steels in face milling. In this study, work materials including different content levels of Al, B and N were cut with a carbide tool P10, a TiN cennet tool, a TiC cermet tool and a TiCN coated carbide tool. When face milling the steels with the carbide tool P10 and the cermet tools at the cutting speed over 200 m/min, steels containing Al, B and N caused much smaller flank wear but larger crater wear than S45C. While in face milling of BN added steels by the TiCN coated tool at the cutting speed of 300 m/min, the crater wear rate was drastically reduced than that of S45C. In the cace of face milling in low oxygen atmosphere, crater wear of the carbide tool were also reduced. It was concluded that the machinability of BN added steels in face milling was influenced by tool materials, Al, B and N content of work materials and cutting atmosphere.

Drilling of Beta-Titanium Alloy.

This study aims to clarify the drilling properties and to find out the optimum drilling procedure for high strength titanium alloy (beta-titanium alloy; Ti-3Al-8V-6Cr-4Mo-4Zr). The various drilling tests with high speed steel (H.S.S.) and carbide drills were conducted under the wet cutting conditions. Cutting force, drill life, drill wear etc. when cutting the alloy were compared with those of Ti-6Al-4V. The results obtained were as follows: (1) The drill geometries recommended for Ti-3Al-8V-6Cr-4Mo-4Zr were the almost same as the geometries for Ti-6Al-4V. (2) Not only the average cutting force but also vibration of the force when drilling Ti-3Al-8V-6Cr-4Mo-4Zr was higher than that of Ti-6Al-4V. (3) In the case of carbide drill, the fracture of cutting edge occurred very frequently by the jamming of chip, and drill life became very short. (4) Carbide solid drill showed over 3 times longer life than H.S.S. drill when smooth chip discharge was achieved by the adoption of the drill cutting edge with nick and the step-feed drilling without the pulling out motion.