I. TECHNICAL ASSESSMENT

Operational tests. Final tests of the set of discs and pads. Assessment of operational parameters, i.e.: braking efficiency, comfort of use, degree and manner of wear, and destructive tests in the laboratory to define the condition of the microstructure of the tested brake discs.

I. BRAKE KIT ASSESSMENT:

Checklist of pre-tests conducted:

• Subjective assessment of braking performance.
• Subjective assessment of user comfort.
• Assessment of the brake discs and pads wear.
• Measurement of brake disc thickness using a micrometer.
• Measurement of brake disc axial runout using a professional dial device.

I.I. Assessment of braking performance and user comfort

The user assessment of the Seat Leon test vehicle shows that ABE Performance disc and pad sets work properly.

a)  Seat Leon vehicle. Test set C3S012ABE-P. Distance of 100 thousand km.

The set of discs and pads was used intensively. A distance of 100,000 km was covered during one year, which allowed us to assess the quality of the test set in many ways.

• Right after installation, there was a noticeable insufficient braking efficiency, which is normal. After driving about 200 kilometres, the effectiveness of the brake kit reached an appropriate level.
• After driving about 9,000 km, there was a noticeable vibration on the steering wheel during braking, which disappeared after about 2,000 km. The vibration had not returned by the end of the tests.
• Braking force effectiveness was good in all operating conditions up to a mileage of about 90,000 km. During rainfall, or when a brake system is cold or hot, no unpredictable reactions during braking were observed.
• During the last 10,000 km, with a total mileage of 90 – 100,000 km, a delayed response with poor braking performance for about 1 – 2 seconds during heavy rain was noticed. We had to get used to this, as the phenomenon always occurred during rainfall. In other situations, the brake set behaved correctly.
• No excessive dust and pollution of aluminum rims was noticed. The degree of dustiness and wear of brake pads remains at a satisfactory level.

The overall subjective assessment of the vehicle user is good. The ABE Performance brake set has shown satisfactory braking performance and efficiency. At this stage, the driver would choose to install ABE Performance brake discs and pads again with no hesitation. At the same time, he would decide to replace the disc and pad set after driving 90,000 km., when the first undesirable symptoms became apparent during heavy rainfall. At this point, the set of discs and pads has been disassembled and the performance tests were considered completed. Total distance covered was 100,000 km.

I.II Condition assessment of test brake assemblies

a) Test set C3S012ABE-P. Distance of 100,000 km.

Fig. 1 View of the brake discs

Fig. 2 View of the right brake disc and pads

Fig. 3 View of the left brake disc and pads

The pads show natural signs of wear and tear, adequate to the mileage. An illustrative thickness measurement of the brake pads was performed: 16.21 mm and 16.36 mm. After covering 100,000 kilometres in mixed mode, mostly highways, the ABE Performance brake set shows natural wear. The manner and range of wear, the thickness values obtained and the run-out tolerances of the brake discs have not reached the limits, therefore making it possible to continue the exploitation of the brake set.

II. Material test of brake discs C3S012ABE-P.

This section presents the results of microstructure tests of the brake discs, both new and used, after a mileage of 100,000 km.

Advanced research techniques were used for the test, using scanning electron microscopy (SEM) and X-ray microanalysis (EDS).

Test Methodology

The analysis was carried out in a specialized independent laboratory. An SEM microscope was used to obtain images of surface topography (SE) and material contrast (BSE). EDS allowed us to define the chemical composition of the studied samples at a depth of 1-4 μm. The presentation of the results includes both microscopic images and spectrograms, which provide valuable data on the elemental composition of the tested sets.

a) Microstructure analysis by light microscopy

– New brake disc – sample Ref

Fig. 4 and Fig. 5 View of the contact and non-contact surface zone with the brake pad (undigested sample) with the brake pad (undigested sample)

Fig. 6 and Fig 7 Microstructure of the core, zone 1 and Fig. 7 Microstructure of the core, zone 2 (un-etched sample)

Fig. 8 Microstructure of the core, zone 3 (undigested sample)

Fig. 9 and Fig. 10 View of the contact and non-contact zone with the brake pad (sample etched with Nital)

Fig. 11 and Fig. 12 Microstructure of the core, zones 1 and 2 (Nital-etched sample)

Fig. 13 and Fig. 14 Core microstructure, zone 3 and Close-up of Fig. 13 (sample etched with Nital)

– Brake disc after exploitation – PP sample

Fig. 15 and Fig. 16 View of the contact and non-contact zone with the brake pad (PP sample, untreated and undigested)

Fig. 17 and Fig. 18 Core microstructure, zone 1 and 2 (PP sample, undigested)

Fig. 19 Microstructure of the core, zone 3 (PP sample, undigested)

Fig. 20 and Fig. 21 View of the contact and non-contact zone with the brake pad (PP sample, etched with Nital)

Fig. 22 and Fig. 23 Microstructure of the core, zones 1 and 2 (PP sample, etched with Nital)

Fig. 24 and Fig. 25 Core microstructure, zone 3 and Close-up of Fig. 24 (PP sample, etched with Nital)

–  Brake disc after exploitation – sample LP

Fig. 26 and Fig. 27 View of the contact and non-contact zone with the brake pad (LP sample, undigested)

Fig. 28 and Fig. 29 Core microstructure, zone 1 and 2 (LP sample, undigested)

Fig. 30 Microstructure of the core, zone 3 (LP sample, undigested)

Fig. 31 and Fig. 32 View of the contact and non-contact zone with the brake pad (LP sample, etched with Nital)

Fig. 33 and Fig. 34 Core microstructure, zone 1 and 2 (LP sample, etched with Nital)

Fig. 35 and Fig. 36 Core microstructure, zone 3 and Close-up of Fig. 35 (LP sample, etched with Nital)

b) Microstructure analysis by the SEM scanning microscope

–  New brake disc – sample Ref

Fig. 37-38 View of brake pad contact surface zone (Ref sample, etched with Nital, SE and BSE images)

Figure 39-40 Close-up of Figure 37 (SE image) and close-up of Figure 37 (BSE image)

Fig. 41 Distribution of elements from Fig. 39, along with marked areas of analysis

Fig. 42 Distribution of each element from Fig. 41

X-ray spectra from Fig. 41 with element content are shown below:

– Brake disc after exploitation – PP sample

Fig. 43 View of the contact surface zone with brake pad (PP sample, etched with Nital, SE image)

Fig. 44 View of the contact surface zone with brake pad (PP sample, etched with Nital, BSE image)

Fig. 45 Close-up of Fig. 43 (SE image)

Fig. 46 Close-up of Fig. 44 (BSE image)

Fig. 47 Distribution of elements from Fig. 45, along with marked areas of analysis

Fig. 48 Distribution of each element from Fig. 45

X-ray spectra from Fig. 47, with the element content, are shown below:

– Brake disc after exploitation – sample LP

Fig. 49 View of the contact surface zone with brake pad (LP sample, etched with Nital, SE image)

Fig. 50 View of the contact surface zone with brake pad (LP sample, etched with Nital, BSE image)

Fig. 51 Close-up of Fig. 49 (SE image)

Fig. 52 Close-up of Fig. 49 (BSE image)

Fig. 53 Distribution of elements from Fig. 51, along with marked areas of analysis

Fig. 54 Distribution of elements from Fig. 52

X-ray spectra of Fig. 53, with the element content, are shown below:

III. CONCLUSIONS

As expected, it’s time for the final test results and observations derived from the exploitation of ABE Performance tested brake kit. The detailed process of exploitation tests and the results of the specialized research on the microstructure of the brake discs are included above in the report.

Experts from the Bureau of Technical Expertise and Training (BETiS) have finally completed the tests of a set assembled in a Seat Leon vehicle, No. C3S012ABE-P. The tests were carried out to assess the comfort of use, and the degree and manner of wear and tear, and specialized research was carried out in the laboratory to determine the state of the microstructure of the tested brake discs after use.

ABE Performance brake discs and pads in a Seat Leon vehicle have covered a mileage of 100,000 km, which should be considered a very good result.

Right after the brake sets were assembled, they needed several hundred kilometres (200 – 300 km) to achieve full braking performance. After the discs and pads were run in, no significant performance issues were found. Only, after a certain mileage (about 9,000 km), vibrations were noticed on the steering wheel during braking, which intensified as the temperature of the brake discs increased. It is important that after a mileage of about 2 thousand km, the phenomenon disappeared, and the vibration did not reoccur up to a mileage of about 90 thousand km.

The effectiveness of the braking system and comfort were rated highly. Over a distance of 90,000 km, no malfunctions and no difference in performance were observed during operation in various conditions, i.e. hot, cold as well as in rain, compared to other well-known and more recognizable manufacturers of brake components.

During the last mileage of about 10,000 km, with a total mileage of 90 – 100,000 km, a delayed response and poor braking performance for about 1 – 2 seconds during heavy rainfall were observed. In other situations, the brake set behaved perfectly.

The degree of wear and tear on the set remains at a satisfactory level:

– C3S012ABE-P discs, after covering 100,000 km., at high-speed routes, have a thickness of 24.10/24.25 [mm] (nominally 25.01 mm) while the minimum thickness, which qualifies discs for replacement, is 22 mm.

Referring to specialized laboratory tests of the brake discs, it should be said that microstructural analysis revealed that both new and used brake discs have microstructures of grey cast iron with lamellar graphite and perlitic matrix. A lower amount of graphite was observed in the contact zones of the brake pads, which is typical of areas exposed to wear.

EDS microanalysis indicated the presence of discharges containing Mn, S, Si, N, O, C, Ce, with differences in the concentrations of these elements that are related to local oxidation of the material.

Despite visible traces of oxidation and less graphite in zones of contact with the pads, the tests showed no significant differences in the microstructures of new and used discs. This is probably due to metallurgical processes that are controlled to ensure high wear resistance of the brake disc material. The presence of specific mineral discharges may also play a role in the self-repair process of the microstructure during exploitation.

It should be said that this test provides important information on the impact of exploitation on the microstructure of brake discs, indicating that even after long-term use, the material preserves properties close to those of new discs.

SEM and EDS analysis is a valuable tool in assessing the quality and durability of brake discs. The presented test results not only confirm the high quality of the materials used in the production of the tested brake discs (C3S012ABE-P), but also provide increased safety for vehicle users.

Summary

Tests carried out have shown that the tested ABE Performance brake set (C3S012ABE-P) meets the stringent requirements for the quality of materials used, safety, performance, and comfort. Without a doubt, they can be an alternative to more well-known and recognizable manufacturers of brake discs and pads. During 90,000 kilometres, the brake discs and pads showed adequate effectiveness and predictability of performance, which should be recognized as a good result. In addition, during specialized laboratory tests, they did not show abnormal traces of structural change resulting from, for example, high temperatures.