Powder blown laser cladding of vertical surfaces

Powder blown laser cladding is widely applied in industry to achieve functional surface modifications for corrosion or wear resistance. Commonly this is deposited in the 1G flat position in accordance to the ASME BPVC Section IX (equivalent to the ISO 6947 PA position). For certain applications, however, especially large and heavy components which are difficult to manipulate, the cladding of vertical surfaces would be beneficial – cladding in 2G horizontal position in accordance to the ASMCE BPVC Section IX (equivalently to the ISO 6947 PC position). The task of cladding vertical surfaces requires a specially designed cladding head. The aim of this report is to present those initial results observed through depositing powder in this attitude using a high power diode laser (HPDL). It was observed that the change of the position of the cladded surface from flat to horizontal or vertical affects the cladding process. The reason for this is that gravity affects the powder stream and weld pool in a different way. An optimized parameter set for the 1G (PA) cladding resulted in inferior clads with extensive dilution leading to inhomogeneous properties within the clad; therefore a specific cladding parameter set for the 2G (PC) position had to be developed. Different laser beam sizes and cladding parameters were investigated with the aim of achieving well bonded, crack-free overlapping beads with minimal dilution. The results indicate that the amount of transport gas and the position of a laser head critically influence the clad quality and that generally a smaller laser spot gives better results.