In tools, manufacturing and machinery, simple coatings still dominate the market; however nanoscale coatings promise unique capabilities due to their multi-functionality such as hardness and ductility, abrasion resistance and transparency and the incorporation of miniature reservoirs of functional agents for corrosion and lubricity.
In the tools, manufacturing and machinery coatings market, nanoscale coatings offer greatly reduced friction, increased wear and corrosion resistance and good protection against high temperature oxidation and have found industrial applications on cutting tools used for dry high-speed machining, parts for textile machines, metal forging and protective glass moulds. By engineering composite materials at the nanoscale it is possible to obtain super hard materials that rival diamond in performance.
Wear resistance
In machining and wear resistant applications, hard coatings are essential for enhancing the wear resistance and toughness properties of cutting tools. Conventional coatings do not meet the needs of current machining and manufacturing requirements as well as nanostructured coatings. When moving parts of a machine are subject to friction, more energy is required to move them, the machine does not operate as efficiently, and the parts have a tendency to wear over time.
Nanocoatings
Surface hardness and the wear resistance of materials can be significantly improved through a nanoparticulate coating making the base material harder and improving the wear resistance of the surface. Nanocoatings result in less friction, requiring less input energy, therefore allowing parts to last longer. A modest increase in water or hydraulic pump efficiency resulting from use of these nanocoatings could reduce U.S. industrial energy usage by 31 trillion BTUs annually by 2030, equivalent to savings of $179 million a year.
Nanocoatings also significantly improve other properties such as toughness and thermal shock resistance of the intended surface for a variety of conventional materials such as ceramics, composites and metal alloys.
Properties
This improvement in wear resistance is attributed to the high hardness and toughness of the nanomaterials, and the change of fracture and material-removal due to ultra fine particle size. Nanoscale multi-layer coatings, which consist of alternating layers of materials, further improve the performance of single-layer nanostructured coatings. When properly tailored, these coatings produce super hardness and super modulus effects.
Nanostructured tungsten carbide-cobalt (WC-Co) has been applied to tools in the metalworking, drilling, and mining industries under severe conditions of high pressure, high temperature, and corrosive environment, However, tungsten carbide’s performance has been limited by brittleness and relatively low toughness compared to metal alloys. As such, cobalt can be added as a ductile metal matrix to improve the fracture toughness, which is a function of microstructural variables including metal content, grain sizes, and contiguity of tungsten carbide grains. Nanocomposites extend the lifetime and robustness of tungsten carbide tools by producing nanostructured tungsten carbide and tungsten carbide-cobalt composite powders with finer and nanoscale grain size.
Nanocomposites of Aluminium oxide (Al2O3) and Zirconium dioxide (ZrO2) are used in high efficiency gas turbines, aerospace and automotive components, corrosion and wear resistant coatings, bone joint cup and head of the bone, ceramic membranes in separation such as hyperfiltration, reverse osmosis and gas separation and catalytic and photocatalytic materials. The mechanical properties of nanostructured ceramics and ceramic composites include considerable hardness, high elastic modulus, high fracture toughness, high strength and high ductility.
Markets
There are already many commercial applications in mechanical structures and in the machining of materials. Target markets are friction management, machine and engine technology are especially large targets of developmental activity. The metal finishing market is estimated to be $32 billion. There is also great commercial potential in engines and devices. The potential market for such coatings and coated articles is very wide range from large scale steel, Ni and Ti alloys sheet products to cutting and processing tools; wear resistant parts for automotive, aircraft/space and chemical industries; biocompatible and wear resistant surgical implants down to miniature parts for electronics and microelectronics, including MEMS.
The uptake of protective nanoscale coatings in the tool industry has been relatively slow as increased cost of adopting the coatings are not concurrent with the level of improvement they currently offer the market over traditional coatings. The following profiles summarise companies producing nanocoatings for application in the tools and machinery protective coatings sector.
