Titanium diboride (TiB2) and titanium carbonitride (Ti(C,N)) coatings are widely used as reinforcing materials in applications demanding high corrosion and wear resistance. In this paper, plain carbon steel has been surface alloyed with TiB2 by plasma transferred arc (PTA) technique using two different gas atmospheres. The first metal matrix composite (MMC) is produced with TiB2 particles and argon as shielding and plasma gas. In addition, a mixture of Ar and 5% N2 was used as shielding and plasma gas for producing of second MMC coating. The microstructure of both alloyed layers consists of primary titanium boride particles surrounded by a eutectic matrix, containing ferrite, eutectic boride, and titanium carbonitrides. The presence of these carbonitrides is more intense in the case of the N-enriched alloyed layer, as it was also proved via X-ray Diffraction. The alloyed layers are susceptible to pitting corrosion in 3.5% NaCl or 1？N H2SO4. The alloyed layer produced with nitrogen mixture gas is slightly more noble than the one produced with pure Ar. The metallic-ferritic matrix corrodes in 6% FeCl3？6H2O leaving TiB2 particles protruding from the matrix. The wear performance of both TiB2 MMC depends on the counterbody (tool steel or alumina ball). 1. Introduction Titanium diboride (TiB2) and titanium carbonitride (Ti(C,N)) hard coatings are widely used in applications demanding high corrosion and wear resistance. As titanium has a strong affinity for boron nitrogen and carbon, it combines with these elements in order to form stable titanium borides, nitrides, and carbonitrides, which can be successfully used as reinforcing materials in metal matrix composites (MMCs). In previous studies, TiN and Ti(C,N) coatings are incorporated on various substrates by cathodic arc ion plating process [1, 2], physical vapour deposition [3], and plasma-assisted chemical vapour deposition [4]. In addition, TiB2 particles reinforce different substrates by electron beam [5, 6], laser [7–11], or pulsed electrode surfacing [10–12] techniques. In this study, two different metal matrix composites reinforced with TiB2 are produced on a plain carbon steel substrate by plasma transferred arc (PTA) technique. The first metal matrix composite (MMC) is reinforced with TiB2 particles, while the second one is a nitrogen-enriched TiB2 MMC. The reinforcement with TiB2 particles is achieved by particles of the initial TiB2 powder, whereas the nitrogen is incorporated into the steel surface from the plasma and shielded gas, which is a mixture of Ar and 5% N2. Following their production,
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