Quasicrystalline Coatings Through Laser Processing: A Study on Process Optimisation and Microstructure Evolution
- PDF / 13,806,473 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 86 Downloads / 167 Views
Quasicrystalline coatings through laser processing: A study on process optimisation and microstructure evolution.
K.Chattopadhyay, K.Biswas, S.Bysakh, G.Phanikumar Department of Metallurgy Indian Institute of Science Bangalore 560012, India and A.Weisheit, R.Galun and B.Mordike IWW, Technical University of Clausthal Clausthal-Zellerfeld, Germany ABSTRACT Composite coatings containing quasicrystalline (QC) phases in Al-Cu-Fe alloys were prepared by laser cladding using a mixture of the elemental powders. Two substrates, namely pure aluminum and an Al-Si alloy were used. The clad layers were remelted at different scanning velocities to alter the growth conditions of different phases. The process parameters were optimized to produce quasicrystalline phases. The evolution of the microstructure in the coating layer was characterized by detailed microstructural investigation. The results indicate presence of quasicrystals in the aluminum substrate. However, only approximant phase could be observed in the substrate of Al-Si alloys. It is shown that there is a significant transport of Si atoms from the substrate to the clad layer during the cladding and remelting process. The hardness profiles of coatings on aluminum substrate indicate a very high hardness. The coating on Al-Si alloy, on the other hand, is ductile and soft. The fracture toughness of the hard coating on aluminum was obtained by nano-indentation technique. The K1C value was found to be 1.33 MPa m1/2 which is typical of brittle materials. INTRODUCTION After the discovery of quasicrystals by Shectman et al. in 1984 [1], it took almost ten years to make these new materials industrially useful. The application of quasicrystals is thought of only after the discovery of stable quasicrystalline systems [2]. These materials exhibit attractive properties such as high hardness [3], low thermal conductivity [4], low density, good oxidation and corrosion resistance [5] and low fiction coefficient [6]. Consequently, these materials are found to be potential candidates for various applications such as wear resistant coatings on ductile materials [7], thermal barrier coatings [4], thermoelectric materials [8]. The QC coated nonstick cookware [9] and high strength maraging steels [10] developed by Sandvik steels are already in the market. QC coating has already been tested as thermal barrier coating in aircraft engines [11]. Laser cladding has been extensively used to obtain wear and corrosion resistant coating on different substrates [12]. Laser cladding involves formation of coating by melting the coating material along with a thin layer of substrate with a high power laser beam normal to the surface. Coating forms due to rapid solidification of the melt with material build up on the substrate. There is very few literatures available on laser cladding of quasicrystalline materials. The first K15.3.1
research work on quasicrystalline phase formation by laser melting of ingots of Al-Cu-Fe was reported by Baumeister et al [13]. Auderbert et al. [14] have shown that it poss
Data Loading...
