Differences in Wear and Material Integrity of NAO and Low-Steel Brake Pads under Severe Conditions

Abstract

In this study, through severe reduced-scale braking tests, we investigate the wear and integrity of organic matrix brake pads against gray cast iron (GCI) discs. Two prototype pad materials are designed with the aim of representing a typical non-metal NAO and a low-steel (LS) formulation. The worn surfaces are observed with SEM. The toughness of the pad materials is tested at the raw state and after a heat treatment. During braking, the LS-GCI disc configuration produces heavy wear. The friction parts both keep their macroscopic integrity and wear appears to be homogeneous. The LS pad is mostly covered by a layer of solid oxidized steel. The NAO-GCI disc configuration wears dramatically and cannot reach the end of the test program. The NAO pad suffers many deep cracks. Compacted third body plateaus are scarce and the corresponding disc surface appears to be very heterogeneous. The pad materials both show similar strength at the raw state and similar weakening after heat treatment. However, the NAO material is much more brittle than the LS material in both states, which seems to favor the growth of cracks. The observations of crack faces suggest that long steel fibers in the LS material palliate the brittleness of the matrix, even after heat damage.

Comprehensive Analysis of Current Primary Measures to Mitigate Brake Wear Particle Emissions from Light-Duty Vehicles

“…However, when using NAO brake pads, the increase in pad wear at high mechanical and thermal loads must also be taken into account. In some cases, this has also been reflected in the emission of particulate matter [12,27]; however, in the current study we did not notice such a trend. In particular, it has been reported that (volatile) ultrafine dust is generated by 'outgassing' of the organic lining matrix [11].…”

“…Since this is the standard friction pairing for the European market, it serves as a benchmark in the following analysis and discussion. At this point, high demands in Europe on the braking performance and temperature stability of the friction systems, especially on German motorways, require somewhat aggressive brake pads, which at the same time lead to correspondingly high wear [27]. In particular, it is the wear of the brake disc that comes to the foreground due to the abrasive effect of the ECE brake pads (cf., Figure 5).…”

Brake Wear and Airborne Particle Mass Emissions from Passenger Car Brakes in Dynamometer Experiments based on Worldwide Harmonized Light-Duty Vehicles Test Procedure Brake Cycle

“…Low-steel type brake pads tend to cause more brake emissions than nonsteel pads because of their high level of aggressiveness toward the corresponding gray iron discs. In addition, brake discs with lower surface hardness have higher brake emissions due to higher disc wear [6,[21][22][23][24][25][26][27][28][29]. On the other hand, there have been reports comparing non-steel and steel pads, where pad and disc wear factors are comparable, but brake emissions are lower for non-steel pads [26,27], so the effect of pad and disc wear factors on brake emissions is complex.…”

Study of the Influence of the Copper Component’s Shape on the Properties of the Friction Material Used in Brakes—Part One, Tribological Properties

“…Its use has been forbidden due to its carcinogenic properties [ 5 ]. In brake pads, it worked perfectly as reinforcement [ 6 , 7 ]. It is a fiber of natural origin, so its production did not cause unnecessary contamination.…”