Chuan Zhen Huang

Research and development of rare-earth cemented carbides

Research, development and application of rare-earth cemented carbides in China are reported and reviewed comprehensively. The adding methods, kinds, forms, contents and acting mechanisms of rare-earth elements are discussed and analyzed in detail. Mechanical properties and cutting performances of these rare-earth-containing cemented carbides are also summarized with detailed analyses and practical application examples in machining various work materials. Problems existing in current research and future research topics in this field are considered further.

Microstructure and Mechanical Properties of Ti(C,N)-TiB2-WC Composite Ceramic Tool Materials

Ti (C,N)-TiB2-WC composite ceramic tool materials with sintering aids such as Ni and Mo were fabricated at a temperature of 1550 °C for 1h sintering duration time in vacuum by a hot-press technique. The microstructure and mechanical properties were investigated. The composite ceramic tool materials were analyzed by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The main phases were composed of Ti (C, N), TiB2, WC and MoC, which indicated that no severe chemical reactions occurred in the composite. The flexural strength, fracture toughness and hardness of Ti (C,N)- 20 wt.%TiB2-WC ceramic material were 795.7 MPa, 6.4 MPa·m1/2 and 19.2 GPa respectively.

The Effect of High Pressure Abrasive Water Jet Cutting Parameters on Cutting Performance of Granite

The effect of cutting parameters such as water pressure, nozzle traverse speed and standoff distance on the granite cutting performance as characterized by kerf width, kerf taper, and striation drag angle are researched with a series of experiments using garnetabrasive and ultra high pressure abrasive water jet numerical control machine tool. The relationship between system pressure and abrasive mass flow rate is also studied. The research results show that the abrasive mass flow rate is only proportional to water pressure and the effect of other cutting parameters is not significant. It is found that an increase in water pressure is associated with an increased kerf width and a decreased kerf taper. The kerf width decreases with the enhancement of nozzle traverse speed, and resulting in a significant increase in kerf taper as the nozzle traverse speed increases. The kerf width increases with the enhancement of standoff distance, and hence it causes a significant increase in kerf taper at the standoff distance domain from 3mm to 4mm and then a little decrease in kerf taper at the standoff distance increasing from 4mm to 5mm. The striation drag angle decreases with an increase in water pressure and a decrease in nozzle traverse speed.

Mechanical property and cutting performance of yttrium-reinforced Al2O3/Ti(C, N) composite ceramic tool material

Effects of yttrium on the mechanical property and the cutting performance of Al2O3/Ti(C,N) composite ceramic tool material have been studied in detail. Results show that the addition of yttrium of a certain amount can noticeably improve the mechanical property of Al2O3/Ti(C,N) ceramic material. As a result, the flexural strength and the fracture toughness amount to 1010 MPa and 6.1 MPam1/2, respectively. Cutting experiments indicate that the developed ceramic tool material not only has better wear resistance but also has higher fracture resistance when machining hardened #45 steel. The fracture resistance of the yttrium-reinforced Al2O3/Ti(C,N) ceramic tool material is about 20% higher than that of the corresponding ceramic tool material without any yttrium additives.

Al2O3/Ti(C0.3N0.7) cutting tool material

Abstract Using a new kind of sintering technique, i.e. repetitious-hot-pressing technique, Al 2 O 3 /Ti(C 0.3 N 0.7 ) cutting tool material was fabricated successfully. This composite has good mechanical properties (Flexural strength 820 MPa, Fracture toughness 7.4 Mpa m 1/2 , Vickers Hardness 20.4 GPa), especially high fracture toughness compared with other Al 2 O 3 -based ceramics. Comparison of the cutting performance of Al 2 O 3 /Ti(C 0.3 N 0.7 ) inserts with those of other two kinds of commercial cutting tool inserts (Brands: SG-4 and LT55) showed that this cutting tool material is suitable for continuously cutting of cast iron, hardened steel, especially intermittent cutting hardened steel.

An Experimental Study on Milling Al2O3 Ceramics with Abrasive Waterjet

The machining performance of Al2O3 ceramics is studied by abrasive waterjet (AWJ) milling experiment. The machined surface characteristics and the effect of process parameters on machined surface quality are analyzed. The results showed that the nozzle traverse speed and traverse feed have a strong effect on the machined surface quality. The effect of process parameters on material volume removal rate and the milling depth is also researched. The results indicated that the material volume removal rate and the milling depth would be increased at the milling conditions of higher water pressure and bigger standoff distance. However, the milling depth will decrease at the milling conditions of higher traverse speed and higher traverse feed, and the material volume removal rate has a complex variation.

Study on the Multi-Scale Nanocomposite Ceramic Tool Material

An advanced ceramic cutting tool material was developed by means of micro-scale SiC particle cooperating with nano-scale SiC particle dispersion. With the optimal dispersing and fabricating technology, this multi-scale nanocomposite may get both higher flexural strength and fracture toughness than that of the single-scale composite. The improved mechanical properties may be mainly attributed to the inter/intragranular microstructure with a lot of micro-scale SiC particles located on the grain boundary and a few nano-scale SiC particles located in the matrix grain. Because of the thermal expansion mismatch between SiC and Al2O3 resulting in the compressive stress on the SiC/Al2O3 interface, the interface bonding strength between Al2O3 and SiC was reinforced, which can compel the crack propagating into the relatively weak matrix when meeting the SiC particle on the boundary; while the alumina grain boundary is not the same strong as the SiC/Al2O3 interface and the Al2O3 grain, therefore the crack propagates sometimes along the Al2O3 grain boundaries and sometimes through the grains, when reaching to the nano-scale SiC particle inside the matrix, the crack was pinned and then deflected to the sub-grainboundaries. These coexisting transgranular and intergranular fracture mode induced by micro-scale and nano-scale SiC and the fining of matrix grain derived from the nano-scale SiC resulted in the remarkable strengthening and toughening effect.

Simulation of Velocity Field of Two-Phase Flow for Gas and Liquid in the Abrasive Water Jet Nozzle

Simulation on velocity field of gas-liquid flow in the abrasive water jet nozzle was studied by the computed fluid dynamics (CFD) software, The complex velocity field of the flow in the abrasive water jet nozzle can be obtained by means of simulation. The study on the effect of the nozzle inner cone angle on the velocity field shows that the cone angle affects the whirlpool’s intension and position of the whirlpool in the nozzle of abrasive water jet (AWJ), and it also affects velocity ‘s magnitude and distribution of the velocity on the cone surface.

Radial-mode abrasive waterjet turning of short carbon–fiber-reinforced plastics

ABSTRACT An experimental study is carried out for single-pass radial-mode abrasive waterjet (AWJ) turning of a short carbon–fiber-reinforced polyetheretherketone (PEEK) specimen to understand the machining process and the effects of major process variables (feed speed, water pressure, abrasive mass flow rate, nozzle tilt angle, and rotational surface speed) on the major machining performance measures, that is, the depth of cut, material removal rate (MRR) and surface roughness. It is found that high water pressure, normal nozzle impact angle and high rotational speed with suitably selected feed speed and abrasive flow rate may be selected to achieve a high MRR without significantly compromising the surface roughness. Mathematical models for the three cutting performance measures are then developed for use in process control.

Analysis of the machining performance and surface integrity in laser milling of polycrystalline diamonds

The increasing use of diamond cutting tools necessitates the development of compatible fabrication technologies for the diamond tools, especially for three-dimensional surfaces with micron scale accuracy and good surface quality. In this article, the formation mechanism of surfaces milled using a nanosecond pulsed laser on polycrystalline diamond and the effect of process parameters on the milling performance such as material removal rate and surface integrity are investigated based on a statistically designed experiment. It is shown that laser milling is a viable technology for three-dimensional processing of polycrystalline diamonds with good machining rates and acceptable surface quality. A microscopy analysis indicates that diamond graphitization can occur on the milled surfaces, and laser pulse energy and pulse overlap have a significant effect on the milled surface morphology. Characterization of the machined surface/subsurface is conducted using Raman spectroscopy, and the relationships between damaged surface layer thickness and process parameters are discussed. It is found that an optimum pulse overlap together with moderate pulse energy may be used, while the scan overlap should be selected in the vicinity of its optimum value at around 50% for a good surface quality while maintaining a high material removal rate.