This paper investigated a failure in a ventilated disc brake in an automobile. The failed brake disc had been in service for approximately 10 years. The observed failure was in the form of radial cracks that appeared to have initiated at the outer edge of the disc brake. The cracks were rather straight with no branching. Optical microscope, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) were used to study the microstructure of the failed disc. Vickers microhardness test was also used to evaluate the hardness of the samples. Results showed that the root cause of crack formation, in this case, was related to the excessive wear in the brake disc. Different wear mechanisms, namely abrasive and adhesive wear, were recognized in the failed specimen. Moreover, the worn surface in some areas was covered with fine oxide particles. These particles appeared to have a significant contribution toward abrasion. To further understand the wear mechanisms, pin-on-disc experiments were also conducted on the samples. Results of the pin-on-disc experiments were compared and correlated to the results obtained from the failed brake disc.

No abstract

No abstract

This paper is an attempt to develop an innovative high strength and ductile Ni/Ni3Al/Ni multilayer composite, using spark plasma sintering (SPS). Ni 3 Al powders were first synthesized by mechanical alloying of elemental pure Ni and Al powders. The synthesized intermetallic powders were then mixed with Ni powders in a way that a Ni/Ni 3 Al/Ni multilayer composite can be achieved. Scanning electron microscope, optical microscope, energy dispersive X-ray spectroscopy (EDS), microhardness, and shear punch tests were used to characterize microstructure and mechanical properties of the synthesized composite. Results show that a rather sharp interface with a perfect metallurgical bonding has formed at the Ni/Ni 3 Al joint. The synthesized multilayer composite has a perfect combination of strength and ductility. The maximum shear strength of Ni/Ni 3 Al/Ni multi-layer composite is significantly higher than that of Ni 3 Al, while its ductility is comparable to that of pure Ni.

No abstract