Yu Can Fu

The Influence of Grinding Parameters on the Superficial Hardening Effect of 48MnV Microalloyed Steel

The current surface strengthening process of microalloyed unquenched and tempered steel components is usually induction or laser quenching treatment. Subsequent to heat treatment, these structural parts are subjected to grinding, during which impairment of hardened materials can be caused by thermo-mechanical influence of the grinding process. This paper studies a new method of surface heat treatment by making use of grinding heat and stress to create favorable microstructures and promote high wear and fatigue resistance. This work outlines the influence of grinding parameters on the superficial hardening effect of 48MnV microalloyed steel. It was found that the thickness and hardness of the treated surface layer could be up to 1.6mm and HV750 respectively. The beneficial microstructure of the layer was created by an enhanced martensite transformation. It is highly possible that the method can be used to incorporate grinding and surface hardening into a single grinding operation to develop a cost-effective production method.

Fabrication of Monolayer Brazed Diamond Tools with Optimum Grain Distribution

A new generational manufacturing technology for diamond tools on brazing process cooperated with optimum distribution of grains is put forward in this paper. Monolayer brazed diamond tools with optimum grain distribution are manufactured and their machining performance is investigated through experiments. The testing results show that this series of diamond tools are certain to have super outstanding machining performance, which provides an innovative technology for manufacturing new generation of superbrasive tools.

Experimental Study on High Speed Milling of γ-TiAl Alloy

This paper deals with the milling machinability of gamma titanium aluminide at speeds of 60-240m/min. The results showed that surface roughness was less than Ra0.44μm at all cutting speeds used in the tests even when the tool wear reached VB0.2mm. The milling forces increased slightly with increasing cutting speed but increased rapidly with the elevated flank wear value especially for the Fy component. Compared to those of titanium alloy TA15, the milling forces of γ-TiAl were 190%, 180% and 200% greater for Fx, Fy and Fz respectively under the same machining conditions. Workpiece surface has a maximum microhardness of approximately 600HV0.100, and the depth of maximum hardened layer was confined to 180μm below the surface. When cut with TiAlN coated carbide tool, tool life was 35 min which was only about 1/2 of that for titanium alloy TA15.

Brazed CBN Grinding Wheel with Ag-Base Filler Alloy

In this paper, the disadvantages of the current CBN (Cubic Boron Nitride) grinding wheels were firstly introduced briefly, for indicating that it was very urgent and important to develop new kinds of grinding wheels with excellent performance to replace the conventional wheels. Then high temperature brazing experiments of monolayer CBN wheels with Ag-Cu-Ti filler alloy were carried out. The result shows that the filler alloy has good wetting capability towards CBN grits. The results of scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis show that, just because during brazing titanium atoms in filler alloys segregated preferentially to the surface of the CBN to form Ti-nitride or Ti-boride layer by reaction between titanium atoms and nitride and boron atoms at elevated temperature, strong chemical joining was formed in the interface between CBN grits and filler alloys. Finally, the contrastive grinding experiments were performed between the monolayer brazed CBN grinding wheels and the electroplated ones. The results show that the brazed wheels have more excellent performance than the latter.

Form and Distribution Characterization of Reaction Products at the Brazing Interface Between Ni-Cr Alloy and Diamond

In order to reveal the size, number, form and distribution characterization of resultant at the brazing diamond interface using Ni-Cr alloy, vacuum furnace brazing was carried out. SEM-EDS microanalyses have shown that during brazing the chromium present in the alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product. X-ray diffraction revealed that the wetting and bonding behaviour on diamond surface by molten Ni-Cr alloy is realized through Cr3C2 and Cr7C3 which are produced by interaction between Cr atoms of Ni-Cr alloy and C atoms of diamond surface at elevated temperatures. Furthermore, the size, number, form and distribution characterization of Cr3C2 and Cr7C3 were discovered and the brazing mechanism for diamond was illuminated. Introduction Much attention has been paid to brazed diamond tools, among which mono-layer tools are born and come into practical use as a new tool. In mono-layer tools, the size, number, form and distribution characterization of resultant at the brazing interface are key factors to determine the adhesion performance and service life. The main bonding method used for brazing diamond is to utilize alloy containing Cr, Ti, Mo, Zr or V, which are all carbide-forming metals, as brazing materials, and then to braze diamond on a metal substrate in vacuum or inert atmosphere. Many papers have reported on the performance evaluation of cutting or grinding tools by machining test, but few have been found to discuss the form and distribution characterization of resultant at the brazing diamond interface. Therefore the basic objective of the present work was the study on the form and distribution characterization of resultant at the brazing diamond interface using Ni-Cr alloy during vacuum furnace brazing. Experimental Procedure Ni-Cr alloy with a suitable composition was used for brazing purpose. The said alloy was applied on the top surface of the steel, followed by sprinkling of diamond grits on it. The brazing was carried out under vacuum atmosphere at moderate temperature. Results and Discussion The appearance of brazing diamond observed by SEM was shown in Fig.1. The result illustrated that diamond grits were effectively wetted and protrusion height of grit could reach more than 2/3 of its size. SEM-EDS microanalyses (Fig.2) have shown that the chromium present in the alloy segregated during brazing towards the diamond surface, most probably to form chromium carbide. The thermodynamic data presented in Table 1 clearly indicate a high chemical stability of chromium carbide than that of diamond. Therefore under the prevalent brazing condition the formation of chromium carbide at the interface is quite expected. Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 151-153 doi:10.4028/www.scientific.net/KEM.259-260.151

Microstructure and Performance of Porous Ni-Cr Alloy Bonded Diamond Grinding Wheel

Although the porous metal bonded diamond grinding wheel, which has recently been developed, had an excellent grinding performance for hard-brittle materials, its applications were only in precision grinding in past study. A new method for fabricating the new porous metal bonded diamond grinding wheel by Ni-Cr alloy as bond and vacuum loose powder sintering was proposed in this paper. The morphology of cross section of the segments and microstructure of interface between diamond grits and bond were analyzed. The wetting mechanism between Ni-Cr alloy bond and diamond is reacting wetting. Machining performance experiments about grinding ratio and surface roughness have been carried out. The testing results show that the porous Ni-Cr alloy bonded diamond grinding wheel has certainly fine machining performance in high grinding force occasion, and the maximal grinding ratio and best surface roughness were 6660 and 1.08 m, respectively.

Machining Performance of Brazed Diamond Wire Saw with Optimum Grain Distribution

A kind of new monolayer brazed diamond wire saw with both chemical bonding at the interface between diamond grits and brazing alloy and optimum grits distribution was made. And a machining performance comparative experiment was carried out between the sintered diamond saw from Italy and the brazed one mentioned above. The sawn material is marble with middle hardness. The testing results show that the wire saw with a brazed bonding diamond grid can achieve two to three times the working efficiency of conventional sintered diamond saw, and the corresponding service life can do 3~4 times. Furthermore, the grits of the brazed diamond wire fail mainly in micro fracture modes other than pull-out ones of the sintered diamond saw grits, indicating the strong retention of brazing alloy to the diamond grits. Almost no grits pulling out for brazed diamond wire saw is the key factor of its longer service life, and the optimum distribution and micro fracture of the brazed diamond wire grits raise the machining efficiency.

Measurement Technique of Grinding Wheel Topography Based on Binocular Stereo Vision

Measurement of the grinding wheel topography and its change in machining process is important for revealing the grinding principle of high-temperature brazed mono-layer super-abrasive grinding wheel. A new approach of measuring grinding wheel topography based on binocular stereovision is presented. Firstly, the binocular images are achieved while the optical axes of the two cameras are parallel, and a corner reflection function algorithm is applied to detect corners. Secondly, in order to get matching corners, optimal matching template is obtained by matching curves. The experimental results show that the sequential similarity matching operation with optimal template has advantages of high accuracy, and less error matching. Finally, the height of the corners is obtained by calculating their parallax on left and right image, and the height error is less than 5%.

High-Speed Turning of Titanium Matrix Composites with PCD and Carbide Tools

High-speed turning tests were performed on vol.10%(TiCp+TiBw)/TC4 composite (TMC) in the speed range of 60-120m/min using PCD and carbide tools to investigate the tool life, tool wear, cutting temperatures and cutting forces. The results showed that the carbide tool was not suit for the machining of TMC. Tool life of PCD was confined to 12 min for all the cutting conditions. Flank wear increased obviously with the increasing cutting speed especially when the cutting speed surpassed 80m/min. PCD tool mainly took place chipping, peeling, abrasive wear and adhesive wear at the rake face and flank. The cutting temperatures of carbide were about 1.5-2.0 times higher than that of the PCD. Under the same cutting condition, cutting temperature of TMC was nearly 100°C higher than that of the TC4 matrix. The cutting forces were confined to 130N and 150N for the PCD and carbide tool respectively. For the carbide the cutting forces slightly decreased when the cutting speed increased from 60m/min to 120m/min. When using the worn tool, the cutting forces significantly decreased with the increasing cutting speed especially for the peripheral force component.

Forces and Chip Morphology of Nickel-Based Superalloy Inconel 718 during High Speed Grinding with Single Grain

Single-grain grinding test plays an important part in studying the high speed grinding mechanism of materials. In this paper, a new experimental system for high speed grinding test with single diamond grain is presented. The differences of surface topography and chip morphology of Inconel 718 machined by single diamond grain and single CBN grain were evaluated. The grinding forces and corresponding maximum undeformed chip thickness were measured under different grinding speeds. The chips, characterized by crack and segment band feature like the cutting segmented chips, were collected to study the high speed grinding mechanism of nickel-based superalloy. The results show that the grinding speed has an important effect on the forces and chip formation, partly due to the temperature variation. As the speed increases, the groove surface becomes smoother.