The structure of nanocomposite layers with Ni matrix and disperse phase Si3N4 and PTFE
Beata Kucharska, Maria Trzaska
Quarterly No. 3, 2012 pages 165-170
DOI:
keywords: composite Ni/PTFE/ Si3N4 coating, Si3N4, PTFE, electrochemical method, microhardness
abstract The surface nickel layers produced by the method of electrochemical reduction are used to protect the substrate material against abrasive wear and corrosion. The incorporation of dispersed phases such as lubricative polytetrafluoroethylene (PTFE) and hard silicon nitride (Si3N4) in a nickel matrix allows one to improve the tribological and corrosive properties. The aim of this work was a study of the influence of the deposition process parameters on the structure of the hybrid composite layers Ni/PTFE/ Si3N4 produced by the electrochemical method. The examinations included composite layers of the nanocrystalline nickel (Ni) matrix with the disperse phases of polytetrafluoroethylene (PTFE) and silicon nitride (Si3N4). The layers were deposited in a Watts bath at a current density of 5 A/dm2, constant stirring rate of 500 rpm and constant phase content of PTFE (50 g/dm3) and Si3N4 (10 g/dm3). The stability of the suspension of the disperse phase in the bath, and uniform incorporation of its particles in the nickel matrix was provided by a cationic surfactant. Nanocrystalline nickel layers and nanocomposite Ni/PTFE layers produced by the electrochemical method were also investigated for comparative purposes. The aqueous dispersion of PTFE particles of a size of 0.1÷0.3 μm and polydisperse Si3N4 powder with rather different particle sizes were used to produce the composite layers. The topography and morphology of the silicon nitride powder and the structures of the produced nickel and composite layers were studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The structural analysis of the produced layers were performed and the crystallite sizes were determined with the X-ray diffraction method. The microhardness of HV 0.02 of the produced layers was determined using Zwick's tester. The completed examinations have shown that hybrid Ni/PTFE/ Si3N4 composite layers are characterized by a cohesive texture and nanocrystalline structure of the nickel matrix.