The MA powder was then plasma sprayed onto weathering steel (Cor-Ten. A242) substrate using ... powder, and nanocrystals in the MA powder and the coating.
JTTEE5 DOI: 10.1007/s11666-014-0065-6 1059-9630/$19.00 Ó ASM International
Satish Tailor, R.M. Mohanty, V.K. Sharma, and P.R. Soni (Submitted October 16, 2013; in revised form December 24, 2013)
6061Al powder with 15 wt.% SiC particulate (SiCp) reinforcement was mechanically alloyed (MA) in a high-energy attrition mill. The MA powder was then plasma sprayed onto weathering steel (Cor-Ten A242) substrate using an atmospheric plasma spray process. Results of particle size analysis and scanning electron microscopy show that the addition of SiC particles as the reinforcement influences on the matrix grain size and morphology. XRD studies revealed embedment of SiCp in the MA-processed composite powder, and nanocrystals in the MA powder and the coating. Microstructural studies showed a uniform distribution of reinforced SiC particles in the coating. The porosity level in the coating was as low as 2% while the coating hardness was increased to 232VHN. The adhesion strength of the coatings was high and this was attributed to higher degree of diffusion at the interface. The wear rate in the coatings was evaluated using a pin-on-disk type tribometer and found to decrease by 50% compared to the 6061Al matrix coating. The wear mechanism in the coating was delamination and oxidative type.
Keywords
aerospace applications, aluminum alloys, automotive applications, ceramic matrix composite feedstock, mechanical alloying feedstock, nanocomposite feedstock, wear-resistant coatings applications
1. Introduction Aluminum matrix composites (AMCs) constitute a class of materials that continue to make major industrial impacts in fields as diverse as aerospace, automotive, and structural applications. 6061-T6 aluminum alloy is one of the most widely used alloys in aircraft and other structural applications, engine pistons and valves, magneto parts, etc. However, low wear resistance is the major limitation of this material. Several attempts have been made to overcome this drawback. Aluminum matrix composites reinforced with ceramic particles have received considerable attention due to the combination of their tribological properties without sacrificing the corrosion resistance of aluminum alloys (Ref 1, 2). Incorporation of Al2O3 or SiC particles in this alloy is increasing; especially in the
Satish Tailor, V.K. Sharma, and P.R. Soni, Department of Metallurgical and Materials Engineering, Malaviya National Institute of Technology, Jaipur 302017, India; and R.M. Mohanty, Council of Scientific and Industrial Research, CSIR-HQS, Rafi Marg, New Delhi 110001, India. Contact e-mail: taylor.nitj@ scientist.com.
Journal of Thermal Spray Technology
automotive industry where wear is the dominant process taking place in pistons, cylinder heads, and connecting rods (Ref 3-9). The effect of adding 10 vol.% of submicron-sized particles of Al2O3 into 6061 aluminum alloy on wear behavior was investigated by Al-Qutub et al. (Ref 10) and a significant improvement in dry wear resistance has been reported. In this respect, the mechanical properties of AMCs can be further enhanced by decreasing the size of ceramic particulates and/or matrix grains from micrometer to the nanometer level. Strength improvements in Al matrix composites of about 20% have been reported (Ref 11). Interestingly, a better ductility of nanostructured nanocomposites compared to nanostructured microcomposites has been reported (Ref 12-14). This is particularly important for structural applications where both high strength and ductility are essential. Mechanical alloying (MA) is well recognized as a method for uniform dispersion of reinforcing particles in the matrix (Ref 15-18). The AMC powders prepared by MA can be deposited onto surfaces of engineering parts using thermal spraying techniques. The coatings prepared by this method exhibit low porosity and high hardness and are relatively well bonded to the substrate being protected. Plasma spray technique is capable of producing denser coatings with superior mechanical properties compared to other thermal spray methods (Ref 15, 17-19). Although there have been several studies on composite coatings with micro-sized hard particles (Ref 20-22), the effect of MA-processed feedstock powder on thermal spray coatings is not well established. The objective of the present work was to investigate the properties of 6061 aluminum alloy matrix coatings containing micro- and nano-sized SiCp developed by means of an approach using MA and the atmospheric plasma spray (APS) process.
Volume 23, Issue 7, pp 1081-1088
Peer Reviewed
Fabrication and Wear Behavior of Nanostructured Plasma-Sprayed 6061Al-SiCp Composite Coating
Peer Reviewed
2. Experimental
hardened steel balls. Ball to powder weight ratio and rotational speed were 10:1 and 350 rpm, respectively. The composite powder mixture was processed in a batch size of 100 g along with 1 wt.% Acrawax carbon (supplied by Lonza Inc., NJ.) as process control agent (PCA). The MA powder was then degassed for one hour at 200 °C in a vacuum of 1 9 102 torr. The MA composite powder was deposited on the grit-blasted weathering steel (Cor-Ten A242) (Table 2) substrates using Sulzer Metco plasma spray equipment with 3 MB gun. APS coatings of the as-received 6061Al and blended 6061A-SiCp powders were also applied onto the substrate for comparison purposes. A coating of about 250 lm thickness was applied in all the cases. The spray parameters are presented in Table 3. The whole concept of 6061Al-SiCp composite powder by MA process and its spraying using APS is schematically shown in Fig. 2.
2.1 Materials 6061Al alloy powder, supplied by the M/S ECKA Granulate Velden GmbH, Germany, with a particle size of
