First let me introduce the problem. I'm investigating the formation of micropits on carburised gear teeth 16MnCr5 DIN 17221 (HRC 62). Since micropitting is due to surface fatigue (cracks initiate at the surface, propagate underneath and remove eventually small particles), shot peening seems to be a possible solution to increase the fatigue resistance.
I,ve read already several papers on the topic but two major questions still remain:
- What is the exact behaviour of shot peened carburised steel under heavy contact stresses (>225kg/mm²)? Is it true that under these conditions, instead of surface cracks, subsurface cracks initiate and propagate very quickly below the layer strenghtened by shot peening?
-What is the effect of shot peening on nitrided gear teeth in regard to surface fatigue resistance?
I would be very thankful if somebody can answer these questions or give some valuable information.
Philippe Baeten
Department of Metallurgy and Material Science
Catholic University of Leuven
Belgium
