Friction material

Abstract

A friction material, such as those belonging to the NAO or LS classes. The friction material is substantially free from copper and includes non-spherical particles in the form of powders and/or fibres each constituted by a preferably ferrous metallic core and by an at least partial coating of core formed at least partially or totally by tin and/or tin compounds, such as intermetallic Fe—Sn compounds.

1 . An asbestos-free friction material comprising:
 at least one fibrous base including inorganic and/or organic and/or metallic fibers, at least one filler and at least one binder, the friction material being substantially free from copper and including non-spherical particles that are constituted by a metallic core of asymmetric shape at least partially coated with a layer of at least one of tin or tin compounds and having a granulometry comprised between 0.2 and 600 microns and wherein the non-spherical particles have a surface area between 0.1 and 0.3 m 2 /g.   
     
     
         2 . The asbestos-free friction material of  claim 1 , further belonging to classes known as NAO or LS. 
     
     
         3 . The asbestos-free friction material of  claim 1 , wherein the metallic core comprises iron. 
     
     
         4 . The asbestos-free friction material of  claim 1 , wherein the metallic core comprises steel. 
     
     
         5 . The asbestos-free friction material of  claim 1 , wherein the metallic core comprises one of iron or steel, and wherein tin is present in the at least partial coating in a form of intermetallic iron-tin compounds of a type Fe x Sn y  (where 1<x<5, 1<y<3). 
     
     
         6 . The asbestos-free friction material of  claim 1 , wherein the metallic core of the non-spherical particles are a ferrous metallic cores that are at least partially coated by the layer of at least one of tin or tin compounds and are present in a percentage by volume comprised between 0.5% and 50%, and wherein an Sn content of said particles is comprised between 20% and 30% by weight of an amount of present particles. 
     
     
         7 . The asbestos-free friction material according to  claim 6 , wherein the layer of at least one of tin or tin compounds contains Fe—Sn intermetallic compounds. 
     
     
         8 . The asbestos-free friction material according to  claim 7 , wherein the Fe—Sn intermetallic compounds are present in a percentage by volume between 3% and 20%. 
     
     
         9 . The asbestos-free friction material according to  claim 6 , wherein the at least partial coating of the ferrous metallic cores forming the non-spherical particles also includes FeMeSn ternary intermetallic compounds, where Me is a different metal than Fe. 
     
     
         10 . The asbestos-free friction material according to  claim 1 , further including:
 lubricants/friction modifiers;   abrasives; and   metallic powders.   
     
     
         11 . A friction element comprising a friction layer of the asbestos-free friction material in accordance with  claim 1 . 
     
     
         12 . A braking system comprising:
 a member to be braked;   a brake disc or a brake drum comprised of cast iron or steel; and   at least one braking member comprising a brake pad or brake shoe, the braking member configured to frictionally engage the member to be braked, wherein the braking member has a friction layer intended to cooperate with the member to be braked, the friction layer comprised of an asbestos-free friction material according to  claim 1 .