Chang-Min Suh, Sang-Yeob Oh, Young-Sik Pyun
The Journal of Mechanical Science and Technology, vol. 24, no. 5, pp.1061-1066, 2010

Abstract : This experimental studies were carried out in order to understand the effects of the PVD coating and the UNSM treatment of HSS55 (high speed steel 55) during the production of the automotive inner pipe by the plastic deformation of S45C. The field test and the SEM images revealed that the PVD coating is necessary in spite of the high compressive residual stresses which were formed at the head of a punch pin. Upon the application of the AlCrN coating with the UNSM treatment the productivity and reliability of a punch pin had improved more than about 2.6 times compared to that of the TiN coating without the UNSM treatment. It is likely that the improvement is caused by the decreased stress concentration factor by the ‘wrapped in oxides’ inside of an abrasion pit. The abrasion pits were mostly generated within range of 5% ~ 50% of the diameter ratio from the end of a pin and reached the maximum value about 17% from the end of a pin.

Keyword : Physical vapor deposition (PVD); Durability; Punch pin; Ultrasonic nanocrystal surface modification (UNSM); Abrasion pit