Issue 8

R. Ghelichi et alii, Frattura ed Integrità Strutturale, 8 (2009) 30-44; DOI: 10.3221/IGF-ESIS.08.03 31 particles in the solid state. The general principle of cold spraying has been described elsewhere in more detail [2-4]. This process is based on the selection of the combination of particle temperature, velocity, and size that allows spraying at the lowest temperature possible. As a consequence, the deleterious effects of high-temperature oxidation, evaporation, melting, crystallization, residual stresses, deboning, gas release, and other common problems for traditional thermal spray methods are minimized or eliminated. Cold-sprayed coatings can be processed with very low numbers of defects and low oxygen contents, and therefore exhibit bulk like properties with respect to electrical or thermal conductivity that are not attainable by normal thermal spray processes [4]. Figure 1 : The schematic drawing of cold gas spray apparatuses [3]. A PPLICATION he cold spray cost model was exercised to predict the “should” cost of making deposits of various complexities. Sensitivity of these “should” costs to input variables such as powder cost, utility and shop rates, deposition precision, etc., was also carried out. This study showed that manufacturing using the cold spray process attacks many aspects of the value simultaneously. Judged against the value stream results, use of this technique accomplished. [5] - Reduction in material input; - Elimination of mold and melt pour cost; - Reduction in rework; - Reduction in finishing; - Large increase in material utilization (cold spray has deposition efficiency of 60-95%). These estimated deposition costs were then used to help develop business cases to show that a cost advantage could be obtained by fabricating parts using the cold spray process [5]. Cold spray technology can be used to produce both protective coatings and prototyping/freeform fabrication in not only strategic industries such as defense and aerospace, but also in various other general industries such as steel, utilities, paper and pulp, etc. High performance materials such as superalloys, MMCs and nanostructured materials are used to produce complex and intricate components of various high tech industries. Established cold spray process can cater to economical and fast prototyping and fabrication of these components. For instance, aluminum and aluminum alloy coatings are being investigated for repair/refurbishment of space shuttle solid rocket boosters and others (aerospace), repair and retrieval of parts and plate stocks used in aircraft structures (aircraft industry), repair/refurbishment of casings (gas turbine), corrosion protection coatings (petrochemicals), brazing/joining (utility) and others. Similar to aluminum, it is being pursued with copper (steel, electronics, aerospace), titanium and tantalum (electronics, bioengineering), etc. There are many other applications for cold spray coating some of them as below [5]: - Corrosion Resistant Coatings (Zn, Al) - Dimensional Restoration and Repair (Ni, Stainless Steel, Titanium, Aluminum) - Wear Resistant Coatings (CrC-NiCr, WC-Co, WCu) - Portable Units for Field Repair - Biomedical – prostheses with improved wear - Aerospace – fatigue-resistant coatings - Chemical – improved corrosion resistance - Mineral processing – improved corrosion and erosion resistance - Die casting – extending die life - Electronics – creating a heat sink or superconductive, magnestostrictive surfaces T