SiC-reinforced Al–12Si alloy coatings were produced using the Cold Gas Dynamic Spraying process. Blends of several compositional variations of Al–12Si and SiC particles were created and subsequently sprayed. The microstructural features of the resulting coatings are examined and the mechanical properties, in particular the adhesion strength and the hardness, of the composite coatings are reported. The results show that, depending on the initial SiC volume fraction of the blend, between 50% and 33% of the SiC in the feedstock powder was retained in the coatings. The adhesion strength of the coatings to their substrates was found to slightly decrease with increasing SiC content while the inclusion of SiC particles within the Al–12Si matrix improved significantly the hardness of the coating.

Properties of SiC-reinforced aluminum alloy coatings produced by the cold gas dynamic spraying process

The work presented in this paper examine the possibility of using the pulsed gas dynamic spraying (PGDS) process as a new production technique of Al–12Si alloy coatings and (Al–12Si + SiC p ) composite coatings using feedstock powder containing 20, 40, and 60 (vol.%) reinforcement particles. In this study the effect of the processing conditions, in particular the gas preheating temperature and pressure and the feedstock particle preheating temperature on the coatings microstructure is investigated in order to optimize the spray parameters. Different analysis techniques (OM, SEM, XRD, and microhardness) as well as adhesion strength testing are used to characterize the coatings produced. Detailed comparisons of powders and coatings microstructure, phase composition, microhardness and adhesion strength are presented and discussed. Moreover similarities and differences with coatings prepared by other techniques, namely thermal spray (TS) and cold gas dynamic spray (CGDS), are presented and discussed. It was found that PGDS allows producing dense Al–12Si alloy coatings and (Al–12Si + SiC p ) composite coatings with good adhesion properties while retaining a large fraction of the SiC p present in the feedstock powder. Using the shear test standard (EN 15340), analysis showed that the adhesion strength of the PGDS coatings was slightly superior to the CGDS coatings, but still lower than TS coatings. It was also demonstrated that the adhesion strength decreases as the SiC content in the coating increases.

SiC particulate reinforced Al-12Si alloy composite coatings produced by the pulsed gas dynamic spray process: Microstructure and properties

Aluminum hybrid composite coatings containing SiC and graphite particles by plasma spraying

The corrosion behaviour of aluminium/silicon carbide (Al/SiC) composite coatings deposited by thermal spray on AZ31, AZ80 and AZ91D magnesium-aluminium alloys was investigated by electrochemical and gravimetric measurements in 3.5 wt.% NaCl solution at 22 °C. Corrosion products were examined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and low-angle X-ray diffraction (XRD). Al/SiC composite coatings in the as-sprayed state revealed high level of porosity with poor bonding at the Al/SiC and coating/substrate interfaces, which facilitated degradation of the magnesium substrates by a mechanism of galvanic corrosion. Cold-pressing post-treatment produced more compact coatings with improved corrosion performance in 3.5 wt.% NaCl compared with as-sprayed coatings.

Corrosion behaviour of Mg/Al alloys with composite coatings

6061Al/Al–SiCp bi-layer composites produced by plasma-spraying process

An aluminum base composite (Al-SiC) powder has been developed for producing plasma sprayed coatings on Al and other metallic substrates. The composite powders were prepared by mechanical alloying of 6061 Al alloy with SiC particles. The concentration of SiC was varied between 20 and 75 vol%, and the size of the reinforcement was varied from 8 to 37 µm in the Al-50 vol% SiC composites. The 44 to 140 µm composite powders were sprayed using an axial feed plasma torch. Adhesion strength of the coatings to their substrates were found to decrease with increasing SiC content and with decreasing SiC particle sizes. The increase in the SiC content and decrease in particle size improved the erosive wear resistance of the coatings. The abrasive wear resistance was found to improve with the increase in SiC particle size and with the SiC content in the composite coatings.

Aluminum-silicon carbide coatings by plasma spraying

http://dl.asminternational.org/itsc/proceedings-pdf/doi/10.31399/asm.cp.itsc1996p0339/440522/itsc1996p0339.pdf

Al-SiC Metal Matrix Composite Coatings by Plasma Spraying

The use in automobile blocks and other critical parts such as cam rods and valves requires superior surface properties. This has led to the development of thermally sprayed surface coatings for this type of component. To impert maximum band strength and superior wear resistance, a plasma sprayed aluminum based composite (Al-SiC) was found to be more suitable than current metallic or ceramic coatings. To eliminate inhomogeneities arising from blended powders, composite powders were prepared by mechanical alloying of 6061 Al alloy with SiC particles. The concentration of SiC was varied between 20 and 75v/o. The size of the reinforcement was varied from 8 to 37μm in the Al-50v/o SiC composites. An organic process control agent was used to modify the morphology of the powders during mechanical alloying. The 44 to 140μm powders were sprayed using an axial feed plasma forch. Adhesion strength, hardness, abrasive and erosive wear resistance of the coatings were assessed.

A. C. D. Chaklader

Papers

Aluminum-silicon carbide coatings by plasma spraying

Al-SiC Metal Matrix Composite Coatings by Plasma Spraying

Processing of composite Al/SiC powders for plasma spraying