Research On Microstructure And Properties Of HVOF Ni60-CeO₂ Composite Coatings On The Surface Of 316L Stainless Steel

With the development of industry,the more requires to materials are put forward.At present,Ni60 self-melting alloy powder is difficult to be used in strong wear and hot corrosion environment,the author was inspired by the addition of rare earth oxide in the melting process to improve the comprehensive properties of the alloy,So the nano CeO₂ strengthening phase was added into Ni60 alloy powder and the Ni60-CeO₂ nanocomposite powder particles were obtained by high-energy ball milling.The Ni60-CeO₂ nanocomposite powder were investigated by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,laser scattering for the particle size analysis,results show that the Ni60-CeO₂ nanocomposite powder which is made by high-energy ball milling is suitable for the HVOF,After milled for 10 h,the CeO₂ nanoparticles are homogeneously distributed on the surface of Ni60 matrix,the average grain size and microstrain of the nanocomposite powder are 27.9nm and 0.32%,the nanocomposite powder shape is ellipsoid and eventually stabilized,after sieved,it can be used for the HVOF.Five coatings with CeO₂ content of 0%,0.5%,1.0%,1.5%,2.0% were fabricated by HVOF on the surface of 316 L stainless steel,the properties of five coatings were analyzed,the results show that the coatings have a lamellar structure,the microhardness,bonding strength and porosity of the Ni60-CeO₂ nanocomposite coatings are better than Ni60 coating because of the fine grain strengthening and purification which is caused by nano CeO₂,the bonding strength and porosity of the Ni60-1%CeO₂ coating are 56 MPa and 2.2%,it shows the better comprehensive performance.In 25?and 300 g load under dry friction conditions,the Ni60-CeO₂ nanocomposite coatings have lower friction coefficient and wear weight loss than Ni60 coating,the wear weight loss increases with the addition of nano CeO₂,which tends to decrease first and then increase and show the characteristics of abrasive wear.When the nano CeO₂ is added in an amount of 1%,the coatings have the small wear weight loss.In the hot corrosion environment at 800?,the Ni60-1%CeO₂ nanocomposite coating generate NiO and Cr₂O₃ oxide film on the surface and oxidation and vulcanization reactions occur within the coating which produces NiCr₂O₄,Ni₃S₂ and CeS,the CeS acts as a pinning effect on the S atom,which hinders the diffusion of S to the interior of the coating,so that the Ni60-1%CeO₂ nanocomposite coating has a small corrosion weight loss and shows good thermal corrosion performance.