Coaxial laser cladding of cobalt-base alloy Stellite^TM 6 on gray cast iron/investigations on friction, wear versus commercial brake pad, and corrosion characteristics

Abstract

Environmental legislation and the electrification of vehicles place increased requirements on brake disks in terms of wear and corrosion resistance. Departing from a preliminary study, the present investigation examined the friction and wear behavior as well as the corrosion properties of Stellite™ 6 coatings on gray cast iron, which were deposited by laser cladding. The friction and wear experiments were conducted on a pin-on-disk tribometer at contact pressures of 1.0 and 2.0 MPa as well as rotation speeds of 0.2, 0.4, 0.6, 0.8, and 2.0 m/s. The pins are manufactured from an automotive semi-metallic brake pad. The friction behavior of gray cast iron and Stellite™ 6 coatings is similar under changing test conditions. The tribological behavior is strongly influenced by the microstructural and mechanical properties of the coatings and the brake pad material. A third body layer of contact patches is formed on Stellite™ 6, which mainly consists of brake pad components. The transformation of the Co-matrix (fcc → hcp), subsurface fatigue, and tribo-oxidation are the main wear mechanism for Stellite™ 6. The electrochemical characteristics were analyzed by potentiodynamic polarization, and the corrosion rate was determined with Tafel plots in 3.5% NaCl solution, respectively. Compared to gray cast iron, Stellite™ 6 coatings have a pronounced corrosion resistance due to the formation of a protective passive layer of Co and Cr oxides. This corrosion resistance is mainly influenced by the microstructure. The corrosion rate of the coatings increases in parallel with the Fe dilution.

Corrosion Stiction in Automotive Braking Systems

“…As an example, Chioibasu et al [ 70 ] reported that the corrosion rate of gray cast-iron brake discs coated with Inconel 718 by direct energy deposition was significantly lower than that of the bare discs. A similar effect is reported also for stellite coatings on gray cast-iron brake discs [ 71 ].…”

Microstructure, Mechanical Properties, and Corrosion Behavior of Co‐Based Stellite 6 Multilayer Overlays Deposited on ASTM A36 Steel by Gas Metal Arc Welding Process

“…This higher corrosion resistance is attributed to the formation of strong Cr and Co oxide films in the hardfaced stellite specimens and it is identical to the previous findings. [62][63][64][65][66][67] Stellite-6 is an excellent corrosion resistance material because of the high-chromium content, enabling it to form a strong oxide film on the surface. [65,68] The passive film formed on the stellite-6-deposited specimen is stable, while the substrate underwent severe corrosion damage and the electrochemical characteristics confirm the corrosion trend.…”

“…The increase in pitting resistance of hardfaced stellite-6 specimen is mainly confirmed by the fraction of Cr, W, and Co fraction from SEM-EDS analysis. [66,67] Further, the overlapped portion of the overlays offers excellent corrosion resistance because of the remelting phenomenon. [72] From the micrographs, it is clear that the pitting is severe at the substrate side.…”

Development of Brake Pad Using Palm Kernel Shell Reinforcement Polymer Composite

“…In this study, voc palm kernel brake are compared to asbestos-containing industrial brake pads. [7] In light of the current state of research, the following objectives have been established for the scope of this study • Development of Break pad using PKS powder, epoxy resin, carbon, Aluminium oxide, Hardener, and calcium carbonate.…”