Nageswaran Tamil Alagan, forskarstuderande inom produktionsteknik vid Högskolan Väst presenterar sin licentiatuppsats med titeln "Textured insert for improved heat extraction in combination with high-pressure cooling in turning of superalloys".
Professor Knut Sörby, Institutt för maskinteknikk og produksjon, Norges teknisk-naturvitenskaplige universitet (NTNU)
Professor Gunnar Bolmsjö, Institutionen för ingenjörsvetenskap, Högskolan Väst
Heat generated in a machining process is a common and critical obstacle faced in today's machining industries. The heat generated in the cutting zone has a direct negative influence on the tool life which, in turn, contributes to increase the manufacturing costs. Especially, in machining of Heat Resistant Super Alloys, HRSA this is a very limiting factor. HRSA are capable of retaining their mechanical strength and hardness at elevated temperatures. This property is advantageous in the application in e.g. aero-engines but also a disadvantage, since it also lowers the machinability significantly.
This work is an attempt to improve the heat transfer from the cutting zone, which would lead to an increase in the tool life. To achieve this goal, the cutting tool has been modified to create an improved interface between the coolant and tool in the high-temperature areas.
Two generations of inserts have been designed and investigated. Firstly, an insert with surface texture features has been created with the purpose of increasing the available surface area for heat dissipation: First generation, Gen I. Secondly, a Gen II was designed as a further improvement of Gen I. Here, several channel features on the rake face were added, going from the contact zone to the near proximity of the cutting edge. This with the purpose of improving access to the coolant closer to the cutting edge.
The experiments were conducted in facing operations of Alloy 718 with uncoated round carbide inserts. All experiments were carried out with high-pressure coolant assistance, with a pressure of 16 MPa on the rake face and 8 MPa on the flank face, respectively.
The two generations of inserts, Gen I and Gen II, were experimentally evaluated by tool wear analysis in comparison with a regular insert. The results show that the tool life increased significantly for the Gen I insert, compared to a catastrophic failure of the regular insert at the same conditions. In the case of the Gen II insert, an increase in tool life by approximately 30 to 40 percent compared to Gen I insert was observed.