Laser surface alloying of titanium alloy with silver: Microstructure, hardness and corrosion property

In this study, silver (Ag) was surface-alloyed in TC4 alloy (Ti6Al4V) with a high-power diode laser (HPDL). The Ag content in the alloyed layers were controlled to be 5 to 24 wt%. The microstructure, hardness and corrosion properties of the alloyed layers are affected by the Ag content. The hardness of TC4 alloy, when laser surface-alloyed with 14 wt% Ag increased from 381 HV0.2 to a maximum value of 569 HV0.2, caused by the formation of hard intermetallic phases (Ti2Ag and TiAg) in the α-Ti matrix. However, with the increase of Ag content to 24 wt% the hardness of the alloy was lowered to 456 HV0.2, result of the formation of a soft Ag-rich phase. In addition, observing a decrease in corrosion resistance of the laser surface-alloyed TC4 with a high Ag content, which is attributed to micro-galvanic effect between the α-Ti and Ti2Ag, TiAg and Ag-rich phase.