Hi mjdrogan
to the Surface Engineering Forum.
Quote:The information above is very useful and relevant to me, but are there any BS EN ISO standards that define the thickness of the case hardening and what hardness tests should be used.
Not sure any of these standards would be particularly helpful in answering your specific question. Usually, this is driven more by customer requirements, part function and materials.
Total case depth I would define as the point/depth where the diffusion element (carbon, nitrogen, etc. depending on process) becomes equal to the core/original material. This may be indicated/specified/measured by:
* hardness traverse - the point where hardness becomes equal to core hardness
* metallography - the point where micro-structural changes equal the core.
* stepped layer chemical analysis
Effective case depth I would define as the point where the diffusion element or hardness reaches a certain specified minimum value.
* hardness traverse - point where minimum specified hardness is achieved.
* metallography - point where specified structural changes occur
* Fractured cross-section
* stepped layer chemical analysis
Value to use to determine effective case depth is usually chosen by customer requirements, part function, materials used and ultimate surface hardness.
Quote:From what you have said and what I already believed Rockwell C is not suitable for 0.35mm nitrided steel surface hardness tests. instead Vickers hardness at 10kgf is far more suitable.
Hardness traverses on cross-section is best done with low load Vickers hardness test or better with micro-hardness test with Vickers or Knoop.
Surface hardness test again Vickers or Knoop. Select load best suited to case depth. Slow and labour intensive as surface requires good quality finishing/polishing. Rockwell and Superficial Rockwell, select scale/load to suit case depth. Fast, simple, better for higher volume (if there is sufficient depth of hardening to support test).