1995 Volume 13 Issue 3 Pages 395-403
The effect of alloying conditions on the formation of alloyed layer on A5083 aluminum alloy surface has been investigated by using plasma transferred arc (PTA) process with TiC as powder alloyed material.
As process parameters, electrode polarity, kind of shielding gas, plasma arc current, powder feeding rate and travel speed were discussed.
The alloying conditions were 100-250 A in plasma arc current, 100-1000 mm/min in travel speed, 5-15 g/min in powder feeding rate with different combination of polarity and shielding gas, namely DCEN-Ar, AC-Ar and DCEN-He.
Alloyed layer with smooth surface can be easily obtained by PTA process with DCEN-He and AC -Ar, but was difficult with DCEN-Ar because molten pool surface was covered with thick oxide film which prevented smooth injection of TiC powder into molten pool.
Higher arc current and lower travel speed made easy to form the alloyed layer.
Injection efficiency (ratio of the gained TiC amount in alloyed layer to TiC amount fed) increased with the increase of a surface area of molten pool and reached almost 100% in DCEN-He.
Volume fraction of TiC in alloyed layer increased with the increase of plasma arc current and powder feeding rate, but was likely to saturate to a limited value.
It was made clear that DCEN-He was the most superior process to show the wider optimum range of alloying conditions even at high travel speed of 500 mm/min and large injection efficiency and volume fraction of TiC than AC-Ar and DCEN-Ar.
This beneficial effect of DCEN-He in PTA process was consider to high temperature of molten pool surface about 1000°C in DCEN-He, which was much higher in AC-Ar of about 700°C, because this high temperature of molten pool enabled the smooth injection of TiC particle into molten Al pool due to good wettability between TiC particle and molten Al.
