Preparation Of Ni-Coated-FeS Powders And Study On Properties Of Its Spraying Coatings

FeS becomes an ideal lubricant on the steel material surface, as excellent friction function and inexpensive cost. Meanwhile along with the development of thermal spraying, FeS is used wider in many kinds of material. In order to prevent the oxidation of FeS in the process of thermal spraying, this article that based on electro less principle takes Nickel sulfate, Sodium hypophosphite and Sodium citrate as raw material and successfully prepared Ni coating FeS powders. Several primary factors were analyzed in the process of electro less. Electro less Ni plating was carried out on the surface of FeS power using AgNO3 as activator to replace the conventional PdCl2 and replacing Sn2+ with H2PO2- as the reducing agent. The best components of solution and plating technology are filtered out by orthogonal experiments. XRD, SEM and metallic micrograph analytical methods were utilized to characterize the properties and microstructure of the FeS. The result indicated that uniform and high quality nickel film can be coated on FeS. Several primary factors was analyzed from two aspects of increasing weight and reaction time, which indicated that reasonable components of solution and plating technology can enhance deposition efficiency. FeS coatings and FeS-Cr3C2 coatings were successfully sprayed on the steel surface with High Velocity Oxygen Fuel spraying and FeS powders and NiCr-Cr3C2 powders. The forming principle, microstructure and properties of the coatings'were researched. Metallic micrograph, XRD and SEM were employed to observe and analyze the morphologies of the surface, cross-section and wear scar of the coatings. The results showed that the coatings have loose surface and machinery interface and they were mainly composed of FeS, a small quantity of Fe1-xS and oxide. With the contents of FeS increasing, the black phase in FeS-Cr3C2 coatings increased, the laminated structure became more obviously, and coatings'porosity increased, however, their binding strength rise at first and then fall with this change.The friction and wear experiment results showed that the sprayed FeS coating possesses the remarkable properties of anti-friction and wear-resistance above 45 steel on dry lubrication. The friction coefficient and wear volume reduced to a very low level. With different FeS content, a variation trend with parabola-shape between the friction properties of different coatings and FeS content. When the FeS content is to 35%, the friction properties of coatings are best. The coatings'wear process generally divided into two stages of run-to-stable and stable, with the different invalid forms, they are caving in and shearing.