Abstract:
Wear resistant surfaces with high toughness and impact resistant properties are
to be created to improve the life cycle cost of brake discs for trains. A potential
solution to this industrial problem is to use an arc cladding process. This work
describes the application of gas tungsten arc welding (GTAW) for a structural
ceramic Metal Matrix Composite (MMC) on steel. The structure of the two
ceramics examined indicates the possibility of development of a wear resistant
surface, which would extend the life of the brake disc. Silicon Carbide (SiC)
and Tungsten Carbide (WC) ceramics were studied to embed them in a steel
matrix by an advanced GTAW method. WC particles penetrated the liquid weld
pool and also partially dissolved in the steel matrix, whereas, SiC because of
the physical properties never penetrated deeper into the weld pool but
segregated on the surface. Successful embedding and bonding of WC led to
the decision to exercise an in-depth analysis of the bonding between the WC
particles and the matrix. Chemical analysis of the matrix revealed more WC
dissolution as compared to particle form within the clad. It was observed that
WC reinforcement particles built a strong chemical bond with the steel matrix.
This was shown by electron backscatter diffraction (EBSD) analysis. The hard
clad layer composed of WC reinforced steel matrix gave an matching friction
coefficient to high-strength steel in cold wear conditions through Pin-on-Disc
wear and friction testing. A prototype railway brake disc was created with the
established GTAW parameters to find out the difficulties of producing industrial
scale components.
