Wear Resistance of HVOF Sprayed Composite Coatings

The aim of the study was to determine the interactions between standard antiwear zinc dialkyldithiophosphate (ZDTP)-type additives and composite coatings containing hard phases of Al₂O₃, SiC, and TiN in the nickel matrix. The analysis was conducted for selected ceramic materials with different structures and different tribological behavior of ionic, covalent, and metallic bonds. The composite coatings were deposited on C45 steel using the high-velocity oxygen-fuel (HVOF) process. This process efficiently uses high kinetic energy and controlled thermal output to produce dense, low porosity coatings with highly predictable chemistries that are homogeneous in structure. The coatings can operate under harsh service conditions, because they are characterized by higher durability and higher wear and corrosion resistance. It was necessary to determine the interactions between the ZDTP-type antiwear additives (zinc dialkyldithiophosphates) and the coatings. The tribological properties of nickel and nickel-based composite coatings were examined by means of a T-01 M tester functioning in the ball-on-disc configuration during technically dry friction and boundary lubricated friction with lubricants containing 1% ZDTP. The comparative analysis confirmed different tribochemical activity and, accordingly, different tribological effectiveness of the nickel and nickel-based composite coatings during friction.