Thermal spray employed for mining equipment? You bet! But before you decide on a thermal spray coating (also known as’hardfacing’), you must first understand the kind of wear. The answers may surprise you.
Abrasive wear can include lower impact, lower stressed conditions. Here, you will see no fracture, no sudden loss in parent material. Rather, material removal is the consequence of scratching, filing, a regular loss in metal at some micro-level. Needless to say, wear rates could be more dramatic when the mined abrasives are sharp, angular in nature. Proper material hardness, such as for example abrasion-resistant steel or ceramic, is key.
Adhesive wear is more of a tearing or material separation between interacting surfaces. It begins with rubbing, and ends with phenomena known as scoring, galling, or seizure. Their occurrence is usually connected with like materials and structure, under an applied load, without lubrication. Here, material choices should consider attributes like ductility, for impact strength. These “softer” alloys available can in fact work harden with impact or deformation. The result is increased strength and resistance to abrasion.
Maybe you have already identified the wear mechanism? Made the appropriate material selection? Well, now it is time to consider thermal spraying. Hardness is the conventional measurement for material choice. Again, remember that, under abrasive conditions, harder material choices, protective coating like tungsten carbide or ceramic coatings are ideal. But also for adhesive wear, where impact strength may be imperative to success, softer, more ductile choices will be the answer.
Did you realize that how (or where) the thermal spray coatings are applied may also decelerate rates of wear? Based on mined material type and shape, the success of a hardface deposit will undoubtedly be in how it is aligned on the surface. Parallel, perpendicular, even coating spacing and overlap could mean the difference between success and failure. Dissimilarity in thermal expansion characteristics between the coating and parent metal is also something to consider.
Any experienced coating provider for mining equipment can tell you: to decelerate wear rates, choose thermal spray.
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William Gunnar, a degreed scientist, researcher, engineer, and friend, has helped a large number of’best of class’product designers and equipment manufacturers — for almost 20 years now — surface engineer with coatings for success.