Optical diagnostics and optimization of the gas-powder flow in the nozzles for laser cladding

Abstract The results of investigation of gas and gas-powder flows in various cladding nozzles are presented and discussed. Schlieren-imaging, high-speed imaging and laser Doppler anemometry were used for optical diagnostics of the flows. It is demonstrated that diameter of the outlet in removable cyclone cap has significant impact on the powder flow pattern in an off-axis nozzle. It provides a convenient way to optimize focusing of the powder flow. It is found that stable vortices that appear near the surface of the substrate significantly reduce efficiency of powder material use when off-axis nozzle is applied. It is demonstrated that excessive shielding gas flow rate in four-stream and coaxial nozzles may lead to defocusing of gas-powder flows. A possibility to increase the efficiency of powder use in various laser cladding nozzles through modification of their design as well as shielding and carrier gases flow rates is discussed.

[1]  B. Laget,et al.  Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components , 2009 .

[2]  A. Gilmutdinov,et al.  Three-dimensional modeling and schlieren visualization of pure Ar plasma flow in inductively coupled plasma torches , 2015 .

[3]  M. Doubenskaia,et al.  Comprehensive analysis of laser cladding by means of optical diagnostics and numerical simulation , 2013 .

[4]  D. Kracht,et al.  Surface texturing by laser cladding , 2011 .

[5]  Radovan Kovacevic,et al.  Numerical simulation and experimental investigation of gas–powder flow from radially symmetrical nozzles in laser-based direct metal deposition , 2007 .

[6]  V. Ocelík,et al.  Analysis of coaxial laser cladding processing conditions , 2005 .

[7]  G. Settles.  Schlieren and shadowgraph techniques , 2001 .

[8]  Igor Smurov,et al.  Physics of Laser Materials Processing: Theory and Experiment , 2011 .

[9]  G. N. Grachev,et al.  Laser-optic Measurements of Velocity of Particles in the Powder Stream at Coaxial Laser Cladding , 2014 .

[10]  Vadim Sufiiarov,et al.  In-situ synthesis of Ti2AlNb-based intermetallic alloy by selective laser melting , 2017 .

[11]  Chi-Chuan Wang,et al.  A visual observation of the air flow pattern for the high speed nozzle applicable to high power laser cutting and welding , 2013 .

[12]  I. Smurov,et al.  Theoretical and Experimental Investigation of Gas Flows, Powder Transport and Heating in Coaxial Laser Direct Metal Deposition (DMD) Process , 2011 .

[13]  Ken Watkins,et al.  Optimisation of layer height control in direct laser deposition , 2004 .