Wen Feng Ding

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.

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.

Grinding Titanium Alloy with Brazed Monolayer CBN Wheels

This paper deals with an investigation of the grindability of Titanium alloy Ti–6Al–4V with brazed monolayer CBN grinding wheels, and systematically studies the effect of process parameters on specific energy and grinding temperature. In the investigation, a groove is machined with a brazed monolayer CBN grinding wheel, and the dimension accuracy of groove has been proved to meet the design requirements. There is no microcrack in surface layer of the groove, and the depth of work-hardening is less than 40 μm, which indicates that the grinding affected zone is small. The results show that brazed monolayer CBN grinding wheels have excellent performance during grinding titanium alloy.

Finite Element Analysis of Residual Stress in Diamond/Steel Brazed Joint

In the application of brazed diamond tools, residual stress caused by differences in materials properties is an important factor in obtaining good brazing quality. The residual stress in diamond/steel brazed joint is studied by means of finite element method and Raman spectroscopy in this paper. The comparison between the results from the simulations and the measurements shows that a good agreement has been reached. Tensile stress concentration at the diamond edge near interface was observed. High residual stress concentration may cause cracks in diamond. Actually, cracks in diamond caused by brazing residual stress after were observed. The stress concentration of the joint must be reduced to obtain good brazed joint. The change of brazing atmosphere or to adopt the soft brazing alloy will reduce the stress concentration.

Grinding Force and Specific Energy in Plunge Grinding of 20CrMnTi with Monolayer Brazed CBN Wheel

In this paper, plunge grinding experiment was conducted on 20CrMnTi with monolayer brazed cubic boron nitride (CBN) wheel. Surface integrity was evaluated through morphology observing and roughness testing. It is found that surface roughness Ra is lower than 0.8μm. Grinding forces were measured and the effects of process parameters (i.e. workpiece speed and depth of cut) on grinding forces were studied. The changing regulation of specific grinding energy with the increase of equivalent chip thickness was revealed. The result shows that both grinding force and specific energy are lower comparing with white fused alumina (WA) wheels. In general, monolayer brazed CBN wheels perform better in grinding of 20CrMnTi than WA wheels.

Wear Behavior of Ti(N,C)-Al2O3 Coated Cemented Carbide Tools during Milling Ti2AlNb-Based Alloy

Ti2AlNb-based alloy is regarded as lightweight high-temperature structural material, which is expected to replace the nickel-base super alloy due to its low density, high elastic modulus, strength retention at elevated temperature, outstanding oxide resistance. However, these excellent properties also make Ti2AlNb to be difficult-to-cut material. In this paper, the milling experiment of Ti2AlNb alloy was carried out using Ti(N,C)-Al2O3 coated cemented carbide tools. SEM and EDS analysis was utilized to observe the worn tools to determine the tool failure modes and wear mechanisms. Tool life when milling Ti2AlNb was short and heavily dependent on the cutting parameters. During milling, coating material of the tool was separated rapidly from the base material. When the cutting speed exceeded 100m/min, serious cracks appeared on the tool surface. Thermal fatigue, adhesive and attrition were the predominant wear mechanisms of the coated tools.

Experimental Investigation on Surface Topography for PTMCs during High Speed Grinding

The present article deals with the surface topography during high speed grinding of particulate reinforced titanium matrix composites (PTMCs). Scanning electron microscopic images of the ground surface was analyzed. Combining the results presented in this paper, the following results could be summarized: (1) The reinforcing particles of PTMCs are removed by means of voids, pulled-out, fracture or crushed, and micro-cracks, which attributed to the plowing and shearing during high speed grinding. (2) The formation of the fracture pattern of PTMCs is formed due to the wear debris of the abrasion during high speed grinding.

Fabrication of Composite Blocks Containing Alumina Bubble Particles for Porous CBN Abrasive Wheels

Alumina (Al2O3) bubble particles were added into the mixture of CBN abrasive grains, Cu-Sn-Ti alloy and graphite particles to prepare the composite blocks for porous CBN abrasive wheels. The specimens were sintered at the temperature of 920°C for the dwell time of 30 min. The bending strength of the composite blocks was measured by the three-point bending tests. The fracture surface of the blocks was characterized. The results show that, the content of alumina bubble particles does not take significant effect on the mechanical strength of the composite blocks. Even the lowest strength of the composite blocks, 98 MPa, is higher than that of the vitrified CBN abra-sive wheels. Cu-Sn-Ti alloy has bonded firmly alumina particles and CBN grains by means of the chemical reaction and corresponding products. Finally, the chip space was formed through the re-moval of the ceramic wall of the alumina bubble particles within the CBN abrasive wheel during dressing.

Grinding Performance of Metal-Bonded CBN Wheels with Regular Pores

Metal-bonded cBN wheels with regular pores were fabricated using Cu-Sn-Ti alloy, cBN abrasive grains and alumina (Al2O3) bubble particles. Dressing experiments were carried out through rotary dressing method. Subsequently, grinding experiments were conducted on nickel-based superalloy GH4169. Comparative grinding performance was evaluated with vitrified cBN wheels in terms of grinding force and specific grinding energy. The results reveal that the pores in the working layer of the cBN wheels are exposed after rotary dressing. Compared to vitrified cBN wheels, grinding forces and specific grinding energy of the newly developed cBN wheels with regular pores are smaller.

Experimental Study on Performance of Monolayer Brazed Diamond Wheel through Chemical-Mechanical Dressing

The dressing methods of monolayer diamond tool have recently been developed increasingly because a substantial improvement of the ground surface roughness could be achieved with the dressed monolayer diamond tools. In this paper, a new dressing method was proposed, namely chemical-mechanical dressing of the diamond grits. Dressing experiments were carried out on the monolayer brazed diamond grinding wheel. The grit-tip distances from the base of wheel substrate were measured before and after dressing. Grinding experiments were conducted on K9 optical glass after each dressing interval. The roughness parameters of the ground surfaces were measured. The outcome of this attempt appeared highly encouraging, and the dressing of monolayer brazed diamond grinding wheel is effective with the chemical-mechanical dressing.