Characterization of tool wear when machining Alloy 718 with high pressure cooling using conventional and surface-modified WC–Co tools

Coolant supplied by high pressure into the cutting zone has shown the lower thermal loads on the tool when machining difficult-to-cut materials as the Alloy 718. In this study, we investigate how the combination of high-pressure cooling and tool-surface modifications can lead to further improvements regarding tool life. The general approach is to enhance the coolant-tool interaction by increasing the contact area. Therefore, we machined cooling features into flank and rake faces of commercially available cemented tungsten carbide inserts. In this way, the surface area was increased by ~ 12 %. After the cutting tests, the tools were analyzed by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Compared with conventional tools, the tool modifications reduced the flank wear by 45 % for the investigated cutting parameters. Furthermore, we were able to significantly increase the cutting speed and feed rate without failure of the tool. The investigated surface modifications have great potential to enhance the productivity of metal cutting processes

The effect of grain size and hardness of Waspaloy on the wear of cemented carbide tools

The effects of grain size and hardness of Waspaloy on the wear of cemented carbide tools were examined by measuring the actual progression of the tool wear in a specific transverse turning operation. Four different conditions of the material from the same batch were studied: fine-grain material in the solution-annealed condition and in the precipitation-hardened condition, as well as large-grain material for the same two conditions. While flank wear, as expected, correlated strongly with hardness, there was basically no effect on the flank wear by the grain size. Notch wear was significant for the large-grain-size material conditions only and was associated with inhomogeneous deformation and burr formation. The deformed layers in the machined surfaces were deeper for the large-grain-size material, but with no obvious effect of hardness

The effect of grain size and hardness of wrought Alloy 718 on the wear of cemented carbide tools

The effects of grain size and hardness of wrought Alloy 718 on the wear of cemented carbide tools were examined by measuring the actual progression of wear in a specific transverse turning operation. Four different conditions of the same material from the same batch were studied fine grain material in the soft, solution annealed state and in the precipitation hardened state, and large grain material in the same two conditions. While flank wear, as expected, correlated strongly with hardness the effect of grain size was much more limited. A striking effect was that of the grain size on the notch wear - one of the limiting factors for tool life - which could be clearly related to the amount of burrs formed in the large grain size material both in the solution annealed and fully precipitation hardened condition. The influence of grain size and hardness on the deformed layer of the work piece material and on the morphology of the chips was clearly visible. (c) 2010 Elsevier B.V. All rights reserved

Feature extraction-based prediction of tool wear of Inconel 718 in face turning

Tool wear is a recurring topic in the cutting field, so obtaining knowledge about the tool wear process and the capability of predicting tool wear is of special importance. Cutting processes can be optimised with predictive models that are able to forecast tool wear with a suitable level of accuracy. This research focuses on the application of some regression approaches, based on machine learning techniques, to a face-turning process for Inconel 718. To begin with, feature extraction of the cutting forces is considered, to generate regression models. Subsequently, the regression models are improved with a reduced set of features obtained by computing the feature importance. The results provide evidence that the gradient-boosting regressor allows an increment in the wear prediction accuracy and the random forest regressor has the capability of detecting relevant features that characterise the turning process. They also reveal higher accuracy in predicting tool wear under high-pressure cooling as opposed to conventional lubrication.The work was performed as a part of the HIMMOVAL project (grant agreement number: 620134) within the Clean Sky programme, which relates to the SAGE2 project oriented to geared open rotor development, enabling the delivery of the demonstrator part. The work of Roberto Santana has been funded by the IT-609-13 programme (Basque Government) and TIN2016-78365-R (Spanish Ministry of Economy, Industry and Competitiveness)

Grit Blasting for Removal of Recast Layer from EDM Process on Inconel 718 Shaft : An Evaluation of Surface Integrity

The heat generated during EDM melts the work material and thereby allows large amounts to be removed, but an unfavorable surface of a recast layer (RCL) will also be created. This layer has entirely different properties compared to the bulk. Hence, it is of great interest to efficiently remove this layer and to verify that it has been removed. The main objective of this work has been to study the efficiency of grit blasting for removal of RCL on an EDM aero space shaft. Additionally, x-ray fluorescence (XRF) has been evaluated as a nondestructive measurement to determine RCL presence. The results show that the grit-blasting processing parameters have strong influence on the ability to remove RCL and at the same time introduce beneficial compressive stresses even after short exposure time. Longer exposure will remove the RCL from the surface but also increase the risk that a larger amount of the blasting medium will get stuck into the surface. This investigation shows that a short exposure time in combination with a short grit-blasting nozzle distance is the most preferable process setting. It was further found that handheld XRF equipment can be used as a nondestructive measurement in order to evaluate the amount of RCL present on an EDM surface. This was realized by analyzing the residual elements from the EDM wire

Surface integrity after post processing of EDM processed Inconel 718 shaft

Electrical discharge machining (EDM) is considered as an efficient alternative to conventional material removal concepts that allows for much higher material removal rates. However, EDM generates unwanted features such as re-cast layer (RCL), tensile residual stresses and a rough surface. In order to recover the surface integrity, different post processes has been compared: high-pressure water jet (HPWJ), grit blasting (GB) and shot peening (SP). Surface integrity has been evaluated regarding microstructure, residual stresses, chemical content and surface roughness. The results showed that a combination of two post processes is required in order to restore an EDM processed surface of discontinuous islands of RCL. HPWJ was superior for removing RCL closely followed by grit blasting. However, grit blasting showed embedded grit blasting abrasive into the surface. Regarding surface roughness, it was shown that both grit blasting and HPWJ caused a roughening of the surface topography while shot peening generates a comparably smoother surface. All three post processes showed compressive residual stresses in the surface where shot peening generated the highest amplitude and penetration depths. However, the microstructure close to the surface revealed that shot peening had generated cracks parallel to the surface. The results strongly state how important it is to evaluate the surface at each of the different subsequent process steps in order to avoid initiation of cracks.First Online: 22 November 2017</p