L. Vijayaraghavan

Chip morphology: an indicator of response of composite material to grinding

MMCs can respond differently neither as a ductile material nor as a brittle material. This is reflected in the morphology of the chip collected during grinding of Al/SiCp metal matrix composite. The chip morphology further depends on condition prevailing over the stagnation zone. In this paper, the observation on chip morphology is correlated with the different process parameters like grinding temperature, acoustic emission and vibration. The results show that chip morphology is a reliable indicator of the response of composite material to grinding.

Grinding of Metal Matrix Composites

The metal-matrix composites are difficult-to-machine materials, since the matrix and reinforcement possess widely-different properties. The manufacturing methodology adopted has significant effect on material and product performance. This chapter presents details on the influence of reinforcement size, grinding abrasive material and grit size on the grindability of Al/SiCp metal-matrix composites. Different performance indicators namely grinding force, temperature and acoustic emission, along with surface texture of the ground surface and chip morphology are discussed.

Effect of cutting parameters on cutting force and surface roughness during machining microalloyed steel: Comparison between ferrite–pearlite, tempered martensite and ferrite–bainite–martensite microstructures

Three different microstructures, namely ferrite–pearlite, tempered martensite and ferrite–bainite–martensite of 38MnSiVS5 microalloyed steel, were produced using controlled thermomechanical processing. The properties are comparable to quenched and tempered steel. The developed microstructures were turned to evaluate their machinability. Mixed modes of response were observed while ferrite–bainite–martensite microstructure exhibits better machinability by way of good surface texture/finish, the ferrite–pearlite microstructure of least strength encounters smaller cutting force.

Effect of microstructure on the surface finish during machining of V-microalloyed steel: Comparison between ferrite–bainite–martensite and ferrite–pearlite microstructures

Multiphase ferrite–bainite–martensite microalloyed steel produced through a two-step cooling followed by annealing route and a ferrite–pearlite steel obtained through air-cooling after forging were subjected to turning operation. The influence of process parameters such as cutting speed, feed and depth of cut on surface roughness on both materials was compared. The results show that the multiphase microalloyed steel exhibited high surface finish than air-cooled steel. The analysis of variance shows that the contribution of cutting speed and depth of cut on surface roughness are insignificant for both ferrite–bainite–martensite and ferrite–pearlite microstructures.

Influence of minimum quantity lubrication on the high speed turning of aerospace material superalloy Inconel 718

Superalloy, Inconel 718 is termed as ‘difficult to cut’ material due to its poor machinability. In order to effectively take advantage of inherent properties such as high temperature resistance, corrosion resistance, creep resistance, and high strength to weight ratio and longer operational life of Inconel 718, it is necessary to improve its machinability. Hence, researchers and industry are working to explore the machinability characteristics of this material particularly with respect to high speed machining (HSM). In these investigations machinability characteristics of Inconel 718 under dry and minimum quantity lubrication (MQL) conditions were evaluated with respect to cutting forces, surface roughness and tool wear using K20 tungsten carbide cutting tool. Moreover, X-ray diffraction analysis of the collected chips was carried out to study the direct effect of dry and MQL cutting conditions to confirm the experimental results obtained. It was observed that machining of Inconel 718 under MQL condition ...

Effect of grinding on subsurface modifications of pre-sintered zirconia under different cooling and lubrication conditions

Pre-sintered zirconia is preferred as a restoration material in dental applications due to its excellent strength and fracture toughness. When abrasive processes were used to obtain the required shape of (Y-TZP) yttria-stabilized tetragonal pre-sintered zirconia, it resulted in material strength degradation in the presence of coolant. Therefore, experiments were carried out on pre-sintered zirconia with diamond grinding wheel to evaluate the performance of cooling conditions such as dry, wet and minimum quantity lubrication (MQL). The effects of different environments on the grinding performance were studied based on the temperature distribution, phase transformation, flexural strength, microhardness and edge chipping damage. The Raman spectroscopy and X-ray diffraction analysis were used to estimate the quantity of monoclinic phase in pre-sintered zirconia. The temperature rise of the workpiece material during the grinding experiment was not higher and insufficient to cause the thermal stresses. The microstructural changes induced by grinding under different cooling strategies were associated with the quantitative assessment of monoclinic phase. The flexural strength of ground components was improved in the dry condition compared to the other process due to the absence of the defective layer and the occurrence of Y3+ ions segregation. After grinding, there was a slight decrease in the hardness value by (1-8 HV), which was due to the formation of microcracks in the subsurface layer of the ground surface. In addition, to ensure the presence of microcracks, the edge chipping depth was measured. The damage depth obtained from the wet condition showed a higher value of 30 µm compared to the dry and MQL conditions.

Temperature measurement during grinding of metal matrix composites

Grinding is a high specific energy process which generates significant amount of heat and has potential to cause surface and sub-surface damage. During grinding of advanced materials like metal matrix composites, which has a relatively softer matrix (Al), it is essential to have better idea of the grinding temperature, so as to reduce/avoid the effects of grinding temperature on the work material being ground. This paper deals with issue related to measurement of temperature during grinding of Al/SiCp metal matrix composites. From the study, it was observed that although the temperature measured by the pyrometer is less owing to factors like emissivity and specific heat capacity, the actual temperature prevalent at the wheel-work interface could have been higher, as confirmed from the SEM of the machined surface.