Dry Sliding Behavior and Particulate Emissions of a SiC-graphite Composite Friction Material Paired with HVOF-Coated Counterface

Abstract

Dry sliding wear tests and corresponding particulate matter (PM) analysis were conducted on a newly developed SiC-graphite-based composite friction material, paired with two types of HVOF counterface/discs: WC-CoCr and WC-FeCrAlY coatings, with a conventional martensitic stainless steel counterface as a reference. The trials were conducted on a pin-on-disc testing equipment at room temperature and a constant sliding velocity and contact pressure of 7 m/s and 0.5 MPa, respectively. The coefficient of friction (CoF) curves with the uncoated disc exhibited considerable fluctuations. On the other hand, the coated discs featured an increase in the CoF at the beginning of the tests, followed by either a continuous reduction until the end of the testing duration or the attainment of a steady state regime. The pin wear and emissions with both coatings were appreciably lower when compared to the trials with the uncoated disc. The evaluation of the friction layer observed a significant contribution of the counterface for all the pairings. The PM analysis was conducted on the particles that were lying in the range of 10 μm and 2.5 μm on a scanning electron microscope (SEM), and particles from 2.5 μm and 1 μm on transmission electron microscope (TEM), with an emphasis on the particles that were detached from the pin surface and friction layer to explain the wear mechanisms for each pairing. Through this, the need for the proper selection of both friction material and counterface to avoid the emission of harmful compounds in the environment was highlighted.

A novel study on the reduction of non-exhaust particulate matter emissions through system vibration control

“…4 a, wherein, the limited extension of the secondary contact plateaus can be observed. Numerous studies 13 – 15 have shown that the predominant PM constituents are detached secondary plateaus. With the high removal of the secondary plateaus in the BC specimens, a naturally high emission magnitude of fine particles (Fig.…”

“…The air from the laboratory (A) is pulled in using a fan (B), which is circulated in a High-Efficiency Particulate Air (HEPA) filter (C) to remove any dust speckles and impurities, thereby, resulting in purified air (particle concentration maintained below 10 #/cm 3 ) being introduced in the PoD chamber (D). The air velocity was maintained at 11.5 m/s 13 . To obtain particle concentration, a TSI ® (TSI Incorporated, Shoreview, USA) Optical Particle Sizer Spectrometer (OPS, model 3330) was connected to the PoD tribometer at Site F in Fig.…”

“…Wear particles, including the emitted airborne particles, are generally a result of the disruption of the secondary plateaus 10 – 14 . As far as the emission evaluation is concerned, by following a pre-defined protocol 13 , 15 , a ‘model scenario’ of PM emissions can be achieved through a pin on disc (PoD) tribometer, as it can be completely enclosed and its ‘environment’ can be easily controlled 3 .…”

A novel path towards limiting non-exhaust particulate matter emissions of a commercial friction material through the addition of metallurgical slag

“…The air from the laboratory (A) is taken in through a fan (B), which was circulated in a High-Efficiency Particulate Air (HEPA) filter (C) to remove any impurities and dust particles and resulting in the introduction of clean air inside the PoD chamber (D). The air velocity was kept at 11.5 m/s, the magnitude obtained from a previous study 31,32 . Before testing, the air cleanliness was rigorously monitored and maintained below 1 #/cm 3 .…”

“…The OPS can measure the total particle number concentration in the size range from 0.3 μm to 10 μm, divided into 16 channels, and with a sampling frequency of 1 Hz. The OPS records and measures particle concentration up to 3000 particles/cm 3 , working with a self-controlled sampling flow rate of 1 l/min 32,33 .…”