Journal of Mechanical Science and Technology

, Volume 24, Issue 1, pp 103–106

Surface durability of WC/C-coated case-hardened steel gear



The purpose of this study is to investigate the influence of tungsten carbide/carbon (WC/C) coating on the surface durability of casehardened steel gear. Two kinds of WC/C coatings were deposited on the ground gear pair made of chromium molybdenum steel with carburizing and quenching. One is the conventional WC/C coating, and the other is WC/C coating with about 1 μm CrN interlayer. Here, the WC/C-coated test pinion and the WC/C-coated one with CrN interlayer are represented by WT and ST, respectively. Non-coated test pinion is represented by NT. The surface roughness along the tooth profile direction of WT and ST was almost the same as that of NT. A spur gear test was carried out with an IAE power circulating type gear test rig under EP gear oil lubricating condition. The fatal failure mode of the test pinions was pitting due to surface cracking. The fatigue life of WT was longer than that of NT under a maximum Hertzian stress pmax=1700 MPa. On the other hand, under pmax=1900 MPa, that of WT was as long as that of NT due to the peeling occurrence of the coated layer. Under the comparatively low load condition without peeling occurrence, the surface roughness of WT decreased with the increasing number of cycles, and their fatigue life became longer than that of NT. On the contrary, in the case of ST, the peeling of the coated layer occurred at a comparatively early stage of the gear test, and the dedendum was worn by tens of micrometers. Therefore, in the case of ST, the effect of the WC/C coating disappeared at a comparatively small number of cycles.


Tribology Gear Surface durability Pitting Wear Surface modification Coating WC/C DLC 


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Copyright information

© The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  1. 1.Graduate School of Natural Science and TechnologyOkayama UniversityOkayamaJapan
  2. 2.Department of Mechanics and RoboticsHiroshima International UniversityHiroshimaJapan

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