The Need for Hardness and Toughness


Toughness is not often discussed by distributors of standard grades of AR plate, such as AR400 or AR500 and their various trade names. Hardness is their primary focus for wear resistance. Hardness is defined as the resistance to penetration, and is necessary where hard or sharp materials are in motion against a solid surface.

However, the “harder the better” is not always true. Wear research has demonstrated that the main way solid surfaces wear out cannot be prevented merely by hardness. Most wear is caused by fracture, defined as the abrupt removal of material by breaking, chipping, or cutting. Examples of fracture wear include knife edges, blades and concrete surfaces. These items are worn not by a gradual removal of the surface or by penetration by hard, sharp objects, but by a chipping and breaking away of the surface particles by fracture. The property that resists fracture is toughness, largely sacrificed in the making of AR plate, but engineered from the start in Mangabraze.

With hard facing and overlays, other engineers have tried to achieve what has always been there in Mangabraze. But why deal with the numerous problems encountered with overlay?

This custom made plate, exclusive to Baldwin, is specially milled for toughness as well as hardness. The 2% level of Manganese (compared to 1% in generic AR plate) allows for the formation of carbides, highly compact binary compounds of carbon and heavy metals, that promote high degrees of wear resistance such as those used in metal-cutting carbide tool bits.

The 1 1/2% level of Nickel (compared to trace – 0.1% in generic AR plate) promotes deeper, more uniform hardening by essentially acting as structural supports within the steel.

What results is a steel that will not crack and will not wear out. Mangabraze is a long-lasting plate that can greatly reduce cost over the long term, can save valuable time, and can prevent the headaches that result from applied plate failure.

Useful Terms

Wear is defined as damage to a solid surface resulting from motion between that surface and any contacting substance.

Types of Wear*:

  1. Abrasion is a type of wear caused by hard particles or protrusions being forced against a surface.
  2. Surface fatigue or fracture occurs when there is extensive and repeated friction between the solid surface and a substance repeatedly sliding or rolling upon it.

Principles of Wear Resistance:

  1. Hardness is the resistance to penetration or abrasion.
  2. Toughness is the resistance to internal fracture created by extensive use.

Only Mangabraze has both.

*other types of wear include erosion and adhesive wear