Surface improvement of laser clad Ti-6Al-4V using plain waterjet and pulsed electron beam irradiation

Laser cladding is a flexible process which can be used to enhance the lifetime of components and repair them when worn. This is especially relevant where components are highly valued, and therefore costly to replace. To date, the surface finish achievable by laser cladding is poor and is characterised by ridges which correspond to the individual beads associated with the process. Increasingly laser cladding is being applied to conformal surfaces which are difficult to process by conventional grinding procedures which may also be ineffective because of discontinuous clad regions. There is therefore a need for a freeform approach which is capable of introducing specific surface finishes to complex components. Hence, in this study, a process chain incorporating plain water jet (PWJ) followed by a pulsed electron beam irradiation was used for the surface modification of laser clad surfaces of Ti-6Al-4V. Initially the surface was characterised by large recesses with peak-trough heights of 200 ± 18 μm and waviness of 49 μm. Upon processing employing water head pressure of 345 MPa impinging the clad surface at an angle 90°, 250 mm/min jet traverse speed, 3 mm stand-off distance and 0.25 mm milling overlap with 2 passes, it was possible to eliminate the peak-trough profile by milling to a depth of 480 ± 10 μm. A flat surface characterised by a surface waviness of 14.9 μm, 12.6 μm Ra and 44 μm straightness was achieved. PWJ milled surfaces were characterised by deep cavities, stepped fractured surfaces, cracks and sub-surface tunnels, however, with application of pulsed electron beam irradiation, most of these surface features were eliminated with a relatively smooth surface produced with 6.2 μm Ra finish.