Workpiece hardening is a central part of any heat treatment facilities' work output, so it's only logical that several alternative techniques should develop in response to this need for mechanical toughness. Let's compare two of these popular hardening techniques. Essentially, we'll be noting the differences that exist between induction hardening and case hardening technology.
Case hardening technology marries heat with chemistry to create a thermochemical process. Conversely, an induction hardened metal part uses pure electromagnetic energy to “induce” an alternating current within the part. The metal uses this contact-free energy gain to electromagnetically generate heat on the surface of the worked component.
Logistically, a case hardened production run can process more parts simultaneously. Batch hardened work pieces pass quickly through the heat treatment facility due to this parallelism benefit. Conversely, the eddy currents generated within an induction processed setting mandate a piece-by-piece approach.
The gas diffusion batch processing method requires a number of sealed parts, including a closed furnace and a carburizing source. Gas parameters and thermal conditions need to be exactingly monitored if repeatable results are to be maintained. Conversely, the adjustment of the electromagnetic frequency ensures precise control of hardening depth, so repeatable results are much easier to achieve.
Again, it's simply a matter of applying the electrical energy in a directed manner that puts this desirable work feature in the induction hardening win column. Localized alloy hardening is accomplished by optimizing a series of scalable magnetic fields. Unfortunately, a case hardened workpiece can only reproduce this methodology by using special pastes to influence the diffusion process. Not surprisingly, this less than scientific approach cannot be counted upon to create reproducible results.
Geometrically complex parts do benefit from the finite control of an electrically controlled induction mechanism, its magnetic fields and frequency-controlled circuits, but case hardened parts leave the inner core of the workpiece entirely untouched. This means the alloy is still relatively flexible and soft, so it's arguably more workable than the induction processed component.
On weighing the pros and cons of both heat hardening methods, the induction technique is the in-line but scalable winner. It works best on crankshafts and on gear teeth as a localized solution. Case hardening solutions, meanwhile, work best on larger, less geometrically detailed components, especially when they require the speed that comes with a batch processing production run.