Coatings for Automotive Gray Cast Iron Brake Discs: A Review

Abstract

Gray cast iron (GCI) is a popular automotive brake disc material by virtue of its high melting point as well as excellent heat storage and damping capability. GCI is also attractive because of its good castability and machinability, combined with its cost-effectiveness. Although several lightweight alloys have been explored as alternatives in an attempt to achieve weight reduction, their widespread use has been limited by low melting point and high inherent costs. Therefore, GCI is still the preferred material for brake discs due to its robust performance. However, poor corrosion resistance and excessive wear of brake disc material during service continue to be areas of concern, with the latter leading to brake emissions in the form of dust and particulate matter that have adverse effects on human health. With the exhaust emission norms becoming increasingly stringent, it is important to address the problem of brake disc wear without compromising the braking performance of the material. Surface treatment of GCI brake discs in the form of a suitable coating represents a promising solution to this problem. This paper reviews the different coating technologies and materials that have been traditionally used and examines the prospects of some emergent thermal spray technologies, along with the industrial implications of adopting them for brake disc applications.

Overview of the French Operational Network for In Situ Observation of PM Chemical Composition and Sources in Urban Environments (CARA Program)

“…The first one-Road transport 1-exhibits a relatively low EC/OC ratio (0.5) and includes almost all antimony and tin measured at this station, whereas the second one-Road transport 2-displays a much higher EC/OC ratio (about 2.6) and a high chromium contribution. These profiles suggest a possible differentiation of (i) light-duty vehicles equipped with gasoline engine and metalloid-lined brakes, and (ii) other types of (heavy-duty) vehicles equipped with diesel engine and/or chrome plated cast iron brakes [85]. Alternatively, it might also be hypothesized that the first factor mainly corresponds to non-exhaust vehicular emissions while the second one is primarily composed of exhaust emissions (with chromium, but also other elements, such as molybdenum or copper, possibly originating from catalyst converters).…”

Mechanical and Magnetic Properties of the High-Entropy Alloys for Combinatorial Approaches

“…Magnets embedded in the discs for regenerative braking induces a current and allows power to be drawn to the electric motor that drives the wheels. There are several material requirements for this application, such as the density, thermal conductivity, thermal expansion, hardness, Poisson's ratio, and Young's modulus [84], while the maximum energy product (BH max , units J m 3 ) is also important. For these applications, Young's modulus-coercive force and Young's modulus-remanent induction relationships are summarized in Figure 5; Figure 6, respectively.…”

Developing Material Requirements for Automotive Brake Disc

“…The prevalence of non-exhaust discharge will attract new legislations and policies from the government in the future. As a consequence of the impending regulations to control non-exhaust emissions, the automakers will be forced to seek for alternative brake disc and pad materials or modify the existing ones using surface treatment technology [9] in order to meet these stringent regulations, and thus, will drive new markets for brake materials in the coming years.…”