Phase composition, microstructure and microhardness of electroless nickel composite coating co-deposited with SiC on cast aluminium LM24 alloy substrate (original) (raw)
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Insight of the interface of electroless Ni–P/SiC composite coating on aluminium alloy, LM24
Electroless nickel composite coatings with silicon carbide, SiC, as reinforcing particles deposited with Ni–P onto aluminium alloy, LM24, having zincating as under layer were subjected to heat treatment using air furnace. The changes at the interface were investigated using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) to probe the chemistry changes upon heat treatment. Microhardness tester with various loads using both Knoop and Vickers indenters was used to study the load effect clubbed with the influence of second phase particles on the coating at the vicinity of the interface. It was observed that zinc was absent at the interface after elevated temperature heat treatment at 400–500 °C. Precipitation of copper and nickel with a distinct demarcation (copper rich belt) along the coating interface was seen with irregular thickness of the order of 1 μm. Migration of copper from the bulk aluminium alloy could have been the factor. Brittleness of the coating was confirmed on heat treatment when indented with Vickers. However, in composite coating the propagation of the microcrack was stopped by the embedded particles but the microcracks continue in the matrix when not interrupted by second phase particles (SiC).
STRUCTURE AND WEAR RESISTANCE PROPERTIES OF ELECTROLESS Ni-P ALLOY AND Ni-P-SiC COMPOSITE COATINGS
European Chemical Bulletin, 2013
To verify the relationship between the properties of composite coatings prepared on steel and the SiC content of electroless Ni-P-SiC composite coatings. Systematic experiments have been conducted to study the possibility of incorporating solid SiC particles in Ni-P matrix. Kinetics of Ni-P plating reveal that the rate of deposition was found to increase linearly with time. The reduction process of nickel ions by hypophosphite was completely hindered at pH < 2and the minimum temperature at which the bath can be practically operated was about 65 ˚C. The mode of deposition of Ni-P film has been explored in the light of deposition condition. XRD analysis of the as-plated and heat -treated samples revealed the existence of crystalline Ni 3 P phases for the heat -treated alloy. Finally a component electroless Ni-P-SiC composite plating process producing a high wear resistance of the coating. *Corresponding Authors *
The electroless nickel composite (ENC) with various silicon carbide contents was deposited onto aluminium alloy (LM24) substrate. The wear behaviour and the microhardness of the composite coating samples were investigated and compared with particles free and aluminium substrate samples using micro-scale abrasion tester and microhardness tester respectively. The wear scar marks and wear volume were analysed by optical microscope. The wear tracks were further studied using scanning electron microscopy (SEM). The embedded particles were found to get pressed into the matrix which helps resisting further wearing process for composite samples. However, random orientation of microcuts and microfallow were seen for ENC sample but more uniform wearing was observed for EN sample. The composite coating with low content of SiC was worn minimum. Early penetration into the substrate was seen for samples with higher SiC content. Microhardness was improved after heat treatment for all the samples containing various SiC content. Under dry sliding condition, inclusion of particles in the matrix did not improve the wearing resistance performance in as-deposited state. The wearing worsened as the content of the particles increased generally. However, on heat treatment, the composite coatings exhibited improved wear resistance and the best result was obtained from the one with low particle contents.
Electrodeposition and Mechanical Characterization of Ni/SiC Composite Coatings
Journal of Nano- and Electronic Physics, 2019
The need to improve coatings for better properties leads to the development of composite electrolytic deposition, by adding insoluble solid particles to the electrolyte. These coatings typically contain ceramic particles in an electrodeposited matrix such as nickel. The aim of this work is to obtain an electrolytic nickel matrix (binder) with and without adding silicon carbide SiC microparticles (mean diameter 0.8 m) which have a high hardness and a good chemical stability. The structural (Ni-SiC) composite and pure nickel coatings were prepared by electroplating deposition on steel in a Watts bath of electroplating chloride. The surface morphology, microstructure, and composition were studied by atomic force microscopy (AFM), nanoindentation, scanning electron microscopy (SEM) and X-ray diffractometer. The characterizations of the deposited layers are carried out in 3.5 % NaCl solution. The weight loss and the polarization results highlighted that the corrosion rate decreases with the increase of SiC concentration up to 15 gl-1. This decrease is probably due to the presence of SiC particles leading to improved corrosion resistance. These properties are mainly due to the homogeneous distribution of the constituents SiC as determined by AFM technique and the possibilities of combining the characteristics of base metals and their coatings. Moreover, the incorporation of the microparticles had a significant impact on the microhardness of the composite deposits Ni-SiC.
Ceramics International, 2014
The formation of a uniform nickel phosphorous (Ni-P) electroless (EL) coating on micron-sized SiC particles was investigated in this study. Metal coated ceramic particles could be used in applications including as the fabrication of cast metal matrix composites.Such ceramic particles have a better wettability in molten metal. In this work, the effects of EL coating parameters, SiC particle size and morphology on the coating uniformity and mechanical bonding at the SiC/Ni-P interface were studied. The results indicated that etching treatment was very effective (especially for coarse powders) on the mechanical bonding at the interface. Theoptimum values of bath temperature and pH were determined to be 50 7 2 1C and 8 7 0.2, respectively. The best uniformity and mechanical bonding were obtained for SiC particles with average particle size of 80 μm (considered relatively as coarse powders in this study). The ball milling of SiC particles (with the average particle size of 80 μm) for 1 h led to the formation of a multi-modal particle size distribution which resulted in a non-uniform quality of particulate coating. The larger SiC particles after ball milling were more completely covered by the Ni-P coating compared to the smaller more fragmented particles. The smaller ceramic particles processed via Ni-P EL coating lead to formation of segregated clusters of Ni-P and therefore such ceramic particles contained many uncoated parts.
The electroless deposition of nickel on SiC particles for aluminum matrix composites
Surface and Coatings Technology, 2004
Nickel coatings have been deposited by an electroless method on SiC powder particles. Three different SiC powder grades, in terms of average particle size, were chosen, i.e. 8, 14 and 70 mm. The coating process was performed in few steps consisting of the SiC powder cleaning by acetone, its sensitization by HCl aqueous solution containing Sn , followed by its activation by 2q HCl aqueous solution containing Pd , and finally-hydrometallurgical nickel deposition using aqueous solution containing 2q Ni , as a nickel carrier. The influence of the deposition conditions on the coating layer properties was studied. The thickness, 2q morphology and microstructure of the layers were controlled by the growth conditions. SEM and digital image analyzing techniques were used for those purposes. Since the Ni-coated SiC powders were produced as reinforcement for Al matrix composites, their compatibility as compared with the uncoated SiC powders was also controlled by metallography.
An attempt has been made to improve the interfacial strength of AlSiC composites which are widely used in defense and automotive sectors. Enhancement of interfacial strength is studied by radial crushing of composites reinforced with electroless nickel coated SiC particled and manufactured by powder metallurgy process. It was visualized that ultimate breaking load for electroless Nickel coated SiC reinforcement has increased by 40 % with respect to uncoated reinforcement. XRD data confirmed the existence of Nickel in Aluminium matrix. SEM studies revealed the incorporation of Nickel with Aluminium and Silicon carbide. Because of improved interfacial strength and microhardness values the so obtained composites can be used for heavy machineries as an alternate to monolithic alloys .