ON RESIDUAL STRESS CHANGES AFTER ORTHOGONAL MACHINING OF INDUCTION HARDENED AISI 4340 STEEL

摘要

The aim of this work is to investigate the residual stress changes induced by dry orthogonal machining of induction surface hardened AISI 4340 steel (58-60 HRC). The machining operations were performed using mixed ceramic inserts. Residual stresses were measured using the X-ray diffraction method and the effects of cutting parameters on the residual stresses are investigated in this work. It was found that dry hard machining induces a compressive residual stress state on the surface and below the machined surface. The residual stress distribution is significantly affected by the cutting feed and the cutting speed. When the cutting feed is increased, the compressive surface residual stresses, the maximum compressive peak and the area of the compressive zone are increased too. However, surface residual stress tends to be tensile when the cutting speed is increased. A thin white layer was observed at a high cutting speed and feed. These results show that hard machining process may be an alternative to grinding since an enhanced surface integrity in terms of residual stresses can be achieved.