TWI Industrial Member Report Summary 1063/2015
By Roger Barnett, Dave Harvey and Tiziana Marrocco
There is considerable industrial interest in the use of cold spray technology for the coating and repair of Al, Mg and Ti alloy airframe and engine components, Ti alloy medical devices, Ni alloy gas turbine components and the use of metal-matrix composite (MMC) coatings for electronic devices. Some materials have thus far proven difficult to deposit and further improvements to coating density, coating adhesion and deposition efficiency are required. The work reported benchmarks new cold spray systems with that operated at TWI since 2007 and describes the effects of process gas type, temperature and pressure on the properties of cold spray deposited nickel alloy 718.
- The new generation of cold spray systems can produce superior nickel alloy 718 coatings due to their ability to operate at higher process gas temperatures and pressures.
- Increasing cold spray process gas pressure leads to coatings with lower levels of porosity and greater adhesion.
- Increasing cold spray process gas temperature also leads to coatings with lower levels of porosity and greater adhesion but with the potential risk of oxidation of the feedstock during spraying.
- The use of helium as a process gas leads to denser, more adherent and stronger coatings than those produced when nitrogen is used as the process gas. This advantage must however be weighed against its much greater cost.