Hardfacing: Overcoming Wear

Do you know the cost of wear for your company?


  It is estimated that 25% of all energy consumed in the world is wasted due to wear. Scary, is not it? This includes the natural loss of friction between parts of mechanical systems, repair and maintenance of equipment damaged by wear.


 A more formal definition of wear can be made as: the phenomenon of progressive removal of material from one surface of a solid body due to mechanical interaction with another solid, liquid or gaseous body.


  Some authors divide the wear into categories as: wear by physical removal of material by microfractures and wear by chemical dissolution. Besides, different mechanisms work within each division, such as adhesive wear, abrasive, fatigue, corrosive, etc.


  Almost all equipment has its durability and reduced reliability due to the wear and tear of its parts. Taking this into account, we realize that the fight against wear has become a necessity of high importance for the advancement of future technologies.


  One way widely used in industry to minimize the negative effects of wear is to act on the selection of surface material exposed to the phenomenon. In many applications the Hard Coating technique, also known as Hardfacing is the best solution.



  It is a controlled deposition of a protective layer on areas that are exposed to exhausting conditions. This layer, also called hardband, can be applied by almost all methods of welding, from oxy-fuel welding (OAW) to more advanced methods like MIG / MAG-AC, Plasma-powder (PTA-P) and LASER Cladding.



  The applications are diverse. Drill bits from oil wells, solid flow extractor blades, extrusion spindles, mill rolls, excavator teeth, among many other applications that require severe wear resistance.


  The coating usually consists of a matrix of ductile metal alloy involving oxides and carbides of high hardness, composing a material classified as a ceramic-metal type composite. This microstructural configuration presents average properties of both parts, generating a hard layer, resistant to the removal of material, but still tenacious.


In order to choose the best coating and deposition process, analyze the requests to which the part will be subjected. It is crucial to understand the wear mechanism as well as the environmental conditions to make the coating selection.


 Hardfacing is a technique of extreme importance for emerging countries, such as Brazil, still dependent on the sale of commodities from mining and agriculture, activities in which the use of Hardfacing has become indispensable today.


We thank Eng. Pedro Jeager for the valuable technical contribution in co-authoring the article.


References:

http://engenheirodemateriais.com.br/2018/03/14/o-custo-mundial-atrito-e-desgaste/ Influence of tribology on global energy consumption, costs and emissions K. Kato and K. Adachi, Modern Tribology Handbook, CRC Press, 2001

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