Laser surface allloying of titanium with vanadiumcarbide and molybdenumdisilicide to improve wear resistance

The wear properties of Titanium and its alloys are particulary interesting. Titanium alloys posses a high specific strength and a good corrosion resistance but comparatively bad tribological properties. Reduction of friction and wear by laser surface treatment assumes therefore particular significance. This paper reports about the surface alloying of Titanium with Vanadiumcarbide (VC) and Molybdenum-disilicide (MoSi₂) using a CO₂-laser. V and Mo stabilize the β phase but do not form compounds with Ti. C and Si show only a low solubility in α and β but form the hard phases TiC and Ti₅Si₃. By varying the process parameters layers with melted depths between 300 and 800 μm and a hardness of 400–750 HV were produced. The VC particles can be dispersed or dissolved. The matrix consists of fine TiC precipitations and a solid solution of (α+β). In the system Ti-Si-Mo a lamellar- and fibre-like eutectic and needle-like (Ti,Mo)₅Si₃ precipitations were formed. The brittleness of the layers was determined by indention with a Vickers pyramid and impact erosion tests.