Recast and oxide formation in laser-drilled acute holes in CMSX-4 nickel single-crystal superalloy

Abstract The present study investigates the effects of four controllable variables on the metallurgy and geometry of acute (30° to surface) laser percussion drilled holes in 2 mm thick flat pieces of nickel superalloy: CMSX-4. Design of experiment (DOE) and statistical modelling were used in the experimental study to understand parameter interactions. Assist gas pressure, nozzle stand-off distance, focal plane position (FPP), and number of pulses were chosen as the independent process variables. A central composite design (CCD) was chosen as it offered the most economical number of experiments for the required information. The response surface method (RSM) was used to develop three models. The significant factors in each model were identified based on the analysis of variance (ANOVA), and the models were checked by complete residual analysis. It was found that a high FPP and high nozzle stand off gave the minimum entrance oxide layer thickness whereas the recast layer was minimized for a zero FPP and high pulse number.

[1]  Juan Carlos Hernandez-Castaneda,et al.  Statistical analysis of ytterbium-doped fibre laser cutting of dry pine wood , 2009 .

[2]  Shrikant V. Joshi,et al.  A statistical approach to determine process parameter impact in Nd : YAG laser drilling of IN718 and Ti-6Al-4V sheets , 2005 .

[3]  Lennie E. N. Lim,et al.  Optimization of laser deep-hole drilling of Inconel 718 using the Taguchi method , 1993 .

[4]  M. Ghoreishi,et al.  Statistical modelling of laser percussion drilling for hole taper and circularity control , 2002 .

[5]  U. Krupp,et al.  Study of the oxide scale integrity on Ni‐base alloy CMSX‐4 during isothermal and thermal‐cycling exposure , 2006 .

[6]  J. Folkes,et al.  Laser drilling of cooling holes in aeroengines: state of the art and future challenges , 2004 .

[7]  William B. Tiffany.  Drilling, Marking And Other Applications For Industrial Nd:YAG Lasers , 1985, Photonics West - Lasers and Applications in Science and Engineering.

[8]  Stephen T. Newman,et al.  State of the art electrical discharge machining (EDM) , 2003 .

[9]  B. Yilbas.  Investigation into drilling speed during laser drilling of metals , 1988 .

[10]  B. Yilbas.  Parametric study to improve laser hole drilling process , 1997 .

[11]  O. B. Nakhjavani,et al.  Optimisation of effective factors in geometrical specifications of laser percussion drilled holes , 2008 .

[12]  S. Sarkar,et al.  Film cooling on a turbine guide vane: A numerical analysis with a multigrid technique , 2001 .

[13]  Nd:Yag Laser Applications Survey , 1983 .

[14]  B. S. Yilbas,et al.  Laser hole drilling quality and efficiency assessment , 2004 .

[15]  Lin Li,et al.  Comparative statistical analysis of hole taper and circularity in laser percussion drilling , 2002 .

[16]  Michael W.S. Lau,et al.  A technical review of the laser drilling of aerospace materials , 1994 .

[17]  Ronald Scott Bunker,et al.  A review of shaped hole turbine film-cooling technology , 2005 .