Laser Texturing as Substrate Preparation Technique for Improved Corrosion Performance on WC-Co HVOF Coatings on AZ91DAuthor : Sachpreet Singh Aulakh, Gagandeep Kaushal and Neeraj Bala
Volume 7 No.2 Special Issue:November 2018 pp 80-86
Substrate preparation plays a vital role in the performance of thermal spray coatings. Adherence of the coating to the substrate depends on surface characteristics like; mechanical interlocking, physio-chemical properties of surface and metallurgical bonding. The surface characteristics depend to great extent on the method used for substrate preparation. In the present study, WC-12Co and WC-17Co coatings were deposited on AZ91D samples prepared using laser texturing as substrate preparation technique. Laser textured substrate was characterized using scanning electron microscopy and surface roughness tester. Bond strength of the coating was determined using ASTM 633C pull off test. SEM was used to study the morphology of the coating; XRD/EDAX techniques were used to study the structure of the coatings. Porosity and micro-hardness of the coatings were also measured. Corrosion performance of the coatings was determined using Potentiodynamic and EIS electrochemical corrosion testing techniques. The coatings are found to have good surface and mechanical properties. Both WC-12Co and WC-17Co demonstrated good corrosion performance during electrochemical testing. However, WC-12Co was found to better protect the AZ91D compared to WC-17Co.
AZ91D, Corrosion, HVOF, Laser Texturing, Substrate Preparation
 Yongshan Tao, Tianyingxiong, Chao Sun, Lingyan Kong et al, ―Microstructure and corrosion performance of a cold sprayed aluminium coating on AZ91D magnesium alloy‖, Corrosion Science, Vol. 52, pp. 3191-3197, 2010.
 R Arrabal, A. Pardo, M.C. Merino, M. Mohedano, P. Casajus, S. Merino, ―Al/SiC thermal spray coatings for corrosion protection of Mg-Al alloys in humid and saline environments‖, Surface & Coatings Technology, Vol. 204, pp. 2767-2774, 2010.
 A Pardo, P. Casajus, M. Mohedano, A.E. Coy, F. Viejo, B. Torres, E. Matykina, ―Corrosion protection of Mg/Al alloys by thermal sprayed aluminium coatings‖, Applied Surface Science, Vol. 255, pp. 6968-6977, 2009.
 M. Magnani, P.H. Suegama, N. Espallargas, S. Dosta, C.S. Fugivara, J.M. Guilemany, A.V. Benedetti, ―Influence of HVOF parameters on the corrosion and wear resistance of WC-Co coatings sprayed on AA7050 T7‖, Surface & Coatings Technology, Vol. 202, pp. 4746–475, 2008.
 HarunMindivan, ―Wear behavior of plasma and HVOF sprayed WC-12Co+6% ETFE coatings on AA2024-T6 aluminum alloy‖, Surface & Coatings Technology, Vol. 204, pp. 1870–1874, 2010.
 M. Barletta, G. gBolelli, B. Bonferroni, and L. Lusvarghi, ―Wear and Corrosion Behavior of HVOF-Sprayed WC-CoCr Coatings on Al Alloys‖, Journal of Thermal Spray Technology, Vol.19, No. 1-2 January 2010.
 M. Campo, M. Carboneras, M.D. Lopez, B. Torres, P.Rodrigo, E. Otero, J. Rams, ―Corrosion resistance of thermally sprayed Al and Al/SiC coatings on Mg‖, Surface & Coatings Technology, Vol. 203, pp. 3224-3230, 2009.
 A. Pardo, M.C.Merino, M. Mohedano, P.Casajus, A.E.Coy, R.Arrabal, ―Corrosion behavior of Mg/Al alloys with composite coatings‖, Surface & Coatings Technology, Vol. 203, pp. 1252-1263, 2009.
 Maria Parco, Lidong Zhao, JochenZwick, Kirsten Bobzin, Erich Lugscheider, ―Investigation of HVOF spraying on magnesium alloys‖, Surface & Coatings Technology, Vol. 201 pp. 3269, 2006.
 R.S.C. Paredes, S.C. Amico, A.S.C.M. d‘Oliveira: ―The effect of roughness and pre-heating of the substrate on the morphology of aluminium coatings deposited by thermal spraying‖, Surface & Coatings Technology, Vol. 200, pp. 3049 – 3055, 2006.
 G. Spur, E. Uhlmann, F. Elbing: ―Dry-ice blasting for cleaning: process, optimization and application‖, Wear, pp. 233–235 _1999, pp. 402–411.
 B.J. Griffiths, D.T. Gawne, and D. Dong: ―The Role of Grit Blasting in the Production of High Adhesion Plasma Sprayed Alumina Coatings‖, Proc. Inst. Mech. Eng., Vol. 211, No. 1, part B, pp. 1-9, 1997.
 S. S. Aulakh, G. Kaushal, ―Substrate preparation & thermal spray coating performance – a review‖, International Thermal Spray Conference & Exposition ITSC, Vol. 324, 28, 2016
 A. Lekatou, D. Sioulas, A.E. Karantzalis, D, Grimanelis, ―A comparative study on the microstructure and surface property evaluation of coatings produced from nanostructured and conventional WC-Co powders HVOF sprayed on Al7075‖, Surface and Coatings Technology, Vol. 276, pp. 539-556, 2015.
 J.M. Guilemany, S. Dosta, J.R. Miguel, ―The enhancement of the properties of WC-Co HVOF coatings through the use of nanostructured and microstructured feedstock powders‖, Surface & Coatings Technology, Vol. 201, pp.1180, 2006.
 Chang-Jiu Li, Guan-Jun Yang, ―Relationships between feedstock structure, particle parameter, coating deposition, microstructure and properties for thermally sprayed conventional and nanostructured
WC–Co‖, International journal of refractory metals and hard materials, Vol. 392, 2013.
 Younis, A.A. Alhammali ―Microstructure, mechanical properties and sliding wear behavior ofthermally sprayed cermet coatings‖, PhD thesis, University of Nottingham, U. K, 2016.
 Y. Danlos⁎, S. Costil, H. Liao, C. Coddet, ―Influence of Ti–6Al–4 V and Al 2017 substrate morphology on Ni–Al coating adhesion — Impacts of laser treatments‖, Surface & Coatings Technology, Vol. 205, pp. 2702–2708, 2011.
 M. Parco, Lidong Zhao, JochenZwick et al, ―Investigation of HVOF spraying on magnesium alloys‖, Surface and Coatings Technology, Vol. 201 3269-3274, 2006.
 M. Couto, S. Dosta, J.M. Guilemany, ―Comparison of the mechanical and electromechanical properties of WC-17 and 12Co coatings onto Al7075-T6 obtained by high velocity oxy-fuel and cold gas spraying‖, Surface and Coatings Technology, Vol. 268, pp. 180-189, 2015.
 M. Magnani, P.H. Suegama, N. Espallargas, S. Dosta et al, ―Influence of HVOF parameters on the corrosion and wear resistance of WC-Co coatings sprayed on AA7050 T7‖, Surface and Coatings Technology, Vol. 202, pp. 4746-4757, 2008.
 G.C. Saha, T. I. Khan, G.A. Zhang, ―Erosion-corrosion resistance of microcrystalline and near nanocrystalline WC-17Co high velocity oxy-fuel thermal spray coatings‖, Corrosion Science, Vol. 53, pp. 2106-2114, 2011.
 A. K. Basak, J.-p. Celis et al, ―Effect of nanostructuring and Al alloying on corrosion behavior of thermal sprayed WC-Co coatings‖, Materials Science & Engineering A, Vol. 558, pp. 377-385, 2012.