Customers may ask for a hard coating, but often what they’re really asking for is a wear resistant coating. What’s the difference and which is better? The answer depends on your specific application. Hardness measures a material’s resistance to permanent deformation (indentation, scratching, bending, etc). Wear Resistance measures a material’s resistance to material loss by continuous mechanical action (rubbing, grinding, abrasion, etc). A material might be wear resistant (“tough”) but not particularly hard, OR a hard material might be wear resistant but not particularly tough….

Wear Resistance (Toughness)

Toughness is a material’s ability to absorb energy and deform without fracturing. For example, think of a car tire. Tires are not particularly hard. You can stick your fingernail in some tires, but the tire bounces right back even after extreme deformation (elastic deformation). Even if a tire is permanently deformed (plastic deformation), it rarely tears or breaks. Yet these same tires take a lonnnnnng time to wear out despite rolling on much harder surfaces. (Yes, a fast car doing a burnout can go through a tire quickly, but you get the point.) Tires also withstand extreme temperatures and shock (potholes). They are tough, they deform, and they absorb a lot of energy before failure. Tires are wear resistant, but they are not very hard.

Hardness

Hard material like glass might have excellent resistance to deformation but can be brittle, susceptible to shock, or can be damaged when exposed to high temperature gradients. Glass is hard and wear resistant, but not “tough”. Some hard materials, like Stellite and Colmonoy, are better at resisting stress and shock than others. Simply asking for a hard material may not be the most appropriate selection criteria for your material. You may end up getting glass when what you REALLY want is rubber.

Palmer Can Help You With Hard Facing and Thermal Spray

Are you tired of continuously replacing your process components time and time again? Do you find yourself “caught between a rock and a hard place” of juggling your short-term budget limitations vs maintaining your equipment with a long-term “cost of ownership” approach? Do yourself a favor – don’t replace your high-wear components before FIRST speaking with Palmer Tool about the potential benefits of HVOF or PTA to EXTEND the service life of your equipment.
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