Roles of Iron Metal Powders in Semi-Metallic Friction Materials
For more than 50 years, iron metal powders have been successfully applied in semi-metallic friction materials for OEM and aftermarket applications in North America. The advantages of using iron metal powders in brake formulations stems from its ability to enhance friction performance, to reduce brake/rotor wear, to make it easier to manufacture brake linings and to provide a cost-effective brake material. However, there are few publications exploring the roles of iron metal powders in friction materials due to manufacturing know-how reasons and/or lack knowledge in understanding powder characteristics of iron metal powders manufactured by different manufacturing methods and processes. On the other hand, more and more modified iron and alloyed iron powders have been developed in last 10 years. Many of them have unique chemical and physical properties and have been found wide applications in different industries including friction. However, the advantages of these modified iron-based powders have not been discussed in the past. This paper investigates the roles of different types of iron metal powders manufactured today and discusses the effect of using various raw materials, production methods and processing technologies on the key characteristics of iron powder such as particle size, particle density, and particle morphology. In order to evaluate the effect of iron metal powders on friction noise and performance, dynamometer tests were performed based on a modified noise testing procedure. The testing results indicated that the difference in powder characteristics of iron metal powder could greatly affect the performance of brake materials, especially on co-efficient of friction and braking noise.