What are the choices?

Surface Hardening

Metalurgical process by which steel is hardened in a superficial pattern by allowing the penetration of a metallurgical hardening additive such as boron and then processing the parts thermically.

Advantages:

  • There is little change in the geometry of the parts and the final process can be machined easily by grinding.

Disadvantages:

  • The thickness of the hardened steel is relatively shallow and thus limits the field of application to parts for which only small dimentional variations are allowed.

There is an upper limit for the hardness reached (about 60Rc). Beyond this limit mechanical problems can occur.

Hardfacing – Hardsurfacing

These terms are interchangeable and define the physical application of a layer of abrasion and/or erosion resistant material over a specific area of a steel component to increase the resistance to abrasion/erosion.

Advantages:

  1. There is a rather large array of materials and processes to choose from for a particular application.
  2. Proper selection of type of material and thickness of application will increase considerably the life of any part compared to the hardest steel (30 times and more).
  3. In some cases, the abrasion resistance of the overlay can be superior to the abrasion rate of the service that the parts are submitted to.
  4. Certain products and processes allow multiple rebuilding of the wear area, thus increasing dramatically the cost effectiveness of the process.
  5. The effectiveness of some processes enable to use a lower grade of steel while maintaining the original strength of the part.

Limitations:

  1. The overlay changes the profile of the parts and this has to be factored in the design.
  2. There is a definite lack of objective comparative information on the various hardsurfacing products and properties thereof, as most of the information is offered by the manufacturer of specific products.
  3. Most products do not lend themselves to proper engineering specifications, as they are dual or multiphase materials and the technical data is sometimes fuzzy.
  4. Site experimentation can be a lengthy process before a decision can be made regarding product and process.