Self-Lubricating Coatings for Elevated Temperature Applications Using A High-Velocity- Particle-Consolidation (HVPC) Process

摘要

Cold Spray or High-Velocity- Particle-Consolidation (HVPC) is a relatively new coating method for the deposition of metals, alloys, polymers, and composite powder-materials onto various substrates without significant heating of the spray powders or substrates. Due to the use of low temperatures and absence of in-flight oxidation and other chemical reactions, thermally vulnerable materials can be deposited without significant material degradation. Given these clear advantages, the objectives of the research detailed herein was to develop self-lubricating composite coatings by using HVPC. For the matrix phase, Nickel was selected due to its success against Ti, as well as its relatively high hardness and wear resistance. Molybdenum-disulfide (MoS2) and Boron Nitride (BN) were employed as the lubricants because of their excellent solid lubricating properties. Admixed, mechanically milled, and pre-coated lube particles were all studied as feedstock powders. The developed coatings were characterized for the distribution of lubricant and presence of porosity using microscopy; coatings with the highest and most homogeneous lubricant distributions were also analyzed for micro-hardness, wear, and bond-strength. Based on the above analysis, it was concluded that the HVPC process can be used for the development of Ni-BN composite coatings with comparable hardness and adhesive strengths relative to Ni coatings. Results indicated a slight reduction of friction that suggest greater amounts of lubricant are required in the coatings. This in turn suggests that, improved coatings may be best achieved by shrinking the size of the lubricant particle and increasing the thickness of the Ni coating. This was the major directive of the research detailed in Part II of this report.