An experimental investigation was conducted to clarify the role of an assist gas during gas-assisted laser-metal drilling for incident laser fluxes on the order of 106 W/cm2. In particular, the effect of change in absorptivity and other thermophysical properties associated with metal oxide formation on laser drilling time was investigated. A 100-W, average power, pulsed Nd-YAG laser was used to drill holes in A16061, Cu, 304 stainless steel, and low C steel. A coaxial nozzle was used to supply an assist gas during the drilling process. The minimum pulse width (drilling time) required to drill a hole through a given thickness of metal sample using argon and oxygen assist gas was determined. The results showed that the oxide formed during laser drilling with oxygen affected the drilling time two ways: 1) by changing the absorptivity of the surface and 2) by changing the temperature required to expel the molten material (due to the difference in melting point of the metal and metal oxide). It was concluded that these two competing effects determine whether an oxygen assist gas jet is helpful in low-power drilling of metals.
ASJC Scopus subject areas
- Condensed Matter Physics