STRUCTURE AND WEAR RESISTANCE PROPERTIES OF ELECTROLESS Ni-P ALLOY AND Ni-P-SiC COMPOSITE COATINGS (original) (raw)
Related papers
Coatings, 2021
The purpose of the study is to assess the influence of SiC particles and heat treatment on the wear behaviour of Ni–P coatings when in contact with a 100Cr6 steel. Addition of reinforcing particles and heat treatment are two common methods to increase Ni–P hardness. Ball-on-disc wear tests coupled with SEM investigations were used to compare as-plated and heat-treated coatings, both pure and composite ones, and to evaluate the wear mechanisms. In the as-plated coatings, the presence of SiC particles determined higher friction coefficient and wear rate than the pure Ni–P coatings, despite the limited increase in hardness, of about 15%. The effect of SiC particles was shown in combination with heat treatment. The maximum hardness in pure Ni–P coating was achieved by heating at 400 °C for 1 h while for composite coatings heating for 2 h at 360 °C was sufficient to obtain the maximum hardness. The difference between the friction coefficient of composite and pure coatings was disclosed b...
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.
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).
Development of electroless NiP–PTFE–SiC composite coating
Surface and Coatings Technology, 2003
Electroless nickel (EN) and EN composite coatings with polytetrafluoroethylene (PTFE) andyor SiC were deposited by chemical deposition. The microstructure analysis was conducted with scanning electron microscopy and X-ray diffraction. Differential scanning calorimetry was used to study the phase transition of the coating during the heat treatment. The mechanical and tribological properties were measured using hardness indentation, scratch test and pin-on-disc wear test. The surface energy was analysed using water droplet surface contact angle measurement. The synergistic effects of SiC and PTFE on the wear and anti-sticking properties of the coatings are discussed.
Ni-P coatings electroplating - A review, Part II: Ni-P composites
2018
Ni-P coatings produced by electrodeposition are characterized by good mechanical, tribological and electrochemical properties, they exhibit catalytic activity and beneficial magnetic behaviour. With subsequent thermal treatment hardness of this binary metal-metalloid system can approach or be even higher than that of hard Cr coatings. Electrochemical co-deposition of homogeneously dispersed second phase particles within the Ni-P metal matrix can result in the enhancement of alloy's favourable properties and in the possibility of completely new engineering applications. The purpose of this paper is to provide a general overview of the research work regarding the electrodeposition of Ni-P matrix based composite coatings. Advances in the research of Ni-P composites reinforced by: SiC, B4C, WC, Al2O3, SiO2, TiO2, CeO2, MWCNT, MoS2, WS2, TiN, hBN, PTFE and their combinations are covered, with the consideration of the main models proposed for the co-deposition of particles, influence ...
Mechanical properties correlated to structure for Ni-P/SiC composite surface coatings
2009
A complex research has been undertaken to obtain and investigate Ni-P/SiC surface coatings on mild steel and on pure Cu, electroplated from an electrolyte having various amounts of micron size SiC particles in suspension (0-80g/litre SiC) and various amounts of the electrochemically active component H 3 PO 3 in the electrolyte (0-20g/litre H 3 PO 3). Ni based solid solutions supersaturated in P have been obtained in the metallic matrix of the composite coating whose P content was increased in steps (0; 8.4; 16.1; 20at.%P). Two types of heat treatments have been applied to the Ni-P/SiC electroplated coatings, either a dehydrogenating annealing at 190 o C or a precipitation aging treatment at 420 o C whose structural effects were investigated by microscopy and X-ray diffraction examination. Various properties have been investigated in non heat treated and in heat treated condition: uniformity of coating thickness and adherence, friction coefficient, Vickers penetration hardness. A special attention was paid to the hardness testing of the coatings at low loads F applied on the indenter in order to avoid any influence from the substrate, and to take into consideration the ISE effect (indentation size effect). Reliable information on the effect of process parameters on the coating hardness have been obtained by considering either H V versus F curves or by deriving a true hardness by means of a mathematical model applied to the experimental data. The precipitation hardening heat treatment was shown to be more powerful in increasing the coating hardness than the mere dissolution of P in the supersaturated Ni based solid solution. An interesting composition having 16.1at.%P and a medium amount of incorporated SiC particles was shown to exhibit the highest hardness in heat treated condition at 420 o C.