Product Code: ICAL08_1104

Laser Alloying of Al with Ti and Ni Based Powders to Improve Wear Resistance and Hardness
Authors:
Lipson Rampedi, CSIR National Laser Centre; Pretoria Southwest Africa
Luyolo Mabhali, CSIR National Laser Centre; Pretoria Southwest Africa
Sisa Pityana, CSIR National Laser Centre; Pretoria Southwest Africa
Presented at ICALEO 2008

Laser surface alloying of aluminium AA 1200 was performed with a 4.4 kW Rofin Sinar Nd:YAG laser to improve its hardness and wear resistance. Alloying was carried out by depositing Ni and Ti based powders with different weight ratios on the aluminium substrate at different laser scanning speeds. The intermetallics formed were examined using optical and scanning electron microscopy and phases identified by XRD and EDX analytical techniques. The abrasive wear tests were conducted in accordance with the ASTM B611-85 standard using silica sand abrasives with the sieve grading of 45 AFS. A homogeneous alloyed layer was obtained at 0.010 m/s and 0.012 m/s laser scanning speed. SEM micrograph consisted of a dendritic microstructure. Preliminary results showed a decrease in hardness as the Ti wt% increased (or Ni wt% decreased). The decrease in the hardness was due to powder being un-dissolved in the melt pool, thus not forming intermetallic phases. The wear resistance also followed a similar trend. Optimum hardness and wear resistance were achieved with 20 wt% Ti and 80 wt% Ni powders at 0.010 m/s laser scanning speed. XRD analysis revealed the intermetallic formed contained NiAl3, Al3Ni2, NiTi and TiAl3.