Wear and scuffing characteristics of composite polymer and nickel/ceramic composite coated piston skirts against aluminum and cast iron cylinder bores

The purpose of this research was to evaluate the tribological behavior and compatibility between coated piston skirts and aluminum or cast iron bore c ounterfaces. Aluminum piston skirts with either composite polymer coatings (CPCs) or nickel/ceramic composite coatings (NCCs) were evaluated. Among th e NCC coated piston skirts, Ni-P-BN showed consistent low wear on either ca st iron or the aluminum bores. The tin plated piston skirt generated low we ar depths on cast iron or 390 Al bore surfaces, but higher wear depths on 4 13 Al or 356 Al bore. All the CPCs generated much less wear on cast iron or aluminum cylinder bores compared with the Ni-P-SiC or Ni-P-Si3N4 Skirt coa tings. Even the wear tests using 413 Al and 356 Al bores showed very low we ar depths. Among the CPCs, two coatings with different percentages of molyb denum disulfide and graphite particles dispersed in the resin generated the lowest wear on 390 Al bore. Using a CPC over a hard-anodized surface, the bore wear depth was further reduced and became much more consistent compare d with using a CPC alone. The response of the coatings to a simulation of t he oil starvation associated with scuffing conditions revealed that the CPC s had intrinsic resistance to scuffing. However, the durability was not ver y good. The Ni-P-BN coating had intrinsic resistance to scuffing and Mod du rability when sliding against 390 Al bore in the unlubricated conditions. T he hard anodized surfaces with the CPCs showed much improved coating durabi lity with good scuffing resistance. (C) 2001 Elsevier Science B.V. All righ ts reserved.