Performance Evaluation of Cryogenically Treated Worn CBN Insert by Turning Process

Abstract

Machining of materials is to produce desired shape and size with smooth surfaces for the performance. Machining is carried out using various cutting tools starting high speed steel to recently developed tools like CBN and PCBN etc. These tools are used to machine difficult to cut materials like high strength alloy steels, stainless steel, Inconel 718, Titanium etc. The inserts used are thrown out or no longer required for finish machining. It can be used for rough machining where smooth surface is not primary important and subjected to subsequent machining using fresh inserts. The used inserts can be used subsequently by subjecting them cryogenic treatment at – 196◦ C in a closed chamber. It is longer process for more than 30 hours in a liquid nitrogen chamber. This treatment gives additional strength to cutting inserts to improve the cutting ability and wear resistance. The components used in high strength applications like an aerospace, automobile industries are treated with cryogenic process to improve wear strength. The operating parameters are cutting velocity, feed rate and constant depth of cut. In this research, CBN inserts after turning for 750 mm length was cryogenically treated and again used with same operating parameters as previous machining conditions. Each inserts were measured for flank wear by Scanning Electron Microscope (SEM) after treatment and re-used with same turning conditions as before. Performances of all inserts used were producing the same results or results near to same. The treated inserts were acting as fresh cutting edges. The results showed that cryogenically processed CBN inserts performed very close to previous results.