Metallization of Various Polymers by Cold Spray

Abstract

Previous results have shown that metallic coatings can be successfully cold sprayed onto polymeric substrates. This paper studies the cold sprayability of various metal powders on different polymeric substrates. Five different substrates were used, including carbon fiber reinforced polymer (CFRP), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), polyethylenimine (PEI); mild steel was also used as a benchmark substrate. The CFRP used in this work has a thermosetting matrix, and the ABS, PEEK and PEI are all thermoplastic polymers, with different glass transition temperatures as well as a number of distinct mechanical properties. Three metal powders, tin, copper and iron, were cold sprayed with both a low-pressure system and a high-pressure system at various conditions. In general, cold spray on the thermoplastic polymers rendered more positive results than the thermosetting polymers, due to the local thermal softening mechanism in the thermoplastics. Thick copper coatings were successfully deposited on PEEK and PEI. Based on the results, a method is proposed to determine the feasibility and deposition window of cold spraying specific metal powder/polymeric substrate combinations.

Investigation of Cold Spray on Polymers by Single Particle Impact Experiments

“…At such a high gun travel speed, the thermal effect, i.e. heating, would be different from the previous experiments (Ref 20) in which successful coatings were obtained at a much lower gun travel speed (25 mm•s -1 ). Considering that the thermal effect may be important for polymeric substrates, a preheating pass was conducted just before the single impact tests to minimize the difference in heating.…”

“…It is widely accepted that the bonding is achieved through the adiabatic shear instability mechanism (Ref 14,16). However, when it comes to the polymeric substrates, the adiabatic shear instability mechanism may not be applicable since the polymers possess largely different mechanical properties when compared to metals; indeed, such a mechanism has barely been observed in experiments ( Ref 3,20,21). Therefore, it is of importance to understand the 3 deposition mechanism for cold spray on polymeric substrates, then a generic method can be generated to practically determine the feasibility of cold spraying a specific metal/polymer combination.…”

“…Therefore, it is of importance to understand the 3 deposition mechanism for cold spray on polymeric substrates, then a generic method can be generated to practically determine the feasibility of cold spraying a specific metal/polymer combination. In a recent paper (Ref 20), we have proposed that cold spray on polymeric substrates should be considered as a two-step process, the development of the first layer followed by the buildup, and each step has its own window. For the development of the first layer, the particle velocity must reach the onset velocity for particle/substrate interlocking; whereas to deposit a thick coating, the conventional critical velocity must be exceeded while the particle velocity should remain below the velocity limit above which the incoming particles will erode the previously deposited layer.…”

“…On the other hand, substrate erosion has been reported as a key issue for thermosets or thermosetmatrix composites; only tin can be directly deposited but with a narrow deposition window (Ref 3,10,21). This discrepancy is attributed to the existence of the relatively abrupt thermal softening for thermoplastics near/above their glass transition temperatures, Tgs (Ref 20,21).…”

Review of Functionally Graded Thermal Sprayed Coatings

“…Consequently, some coatings protecting their surface were useful [364]. Thermoplastic polymers are easier to be coated than thermosetting polymers because of their thermal softening [365][366][367]. However, particularly interesting for industrial applications are polymer matrix composite (PMC) such as e.g., such with the polyimide resin as a matrix.…”