High temperature oxidation resistant coatings produced by electro-spark deposition

A simple but efficient technique has been developed to produce surface coatings on metals and alloys. The technique uses direct high frequency electrical sparks to melt and deposit metal or alloy coatings onto the substrate surface. This paper reports on Al and FeCrAl coatings on AISI 304 stainless steel. Cyclic oxidation tests at 1000 degreesC in air showed that the oxidation rates of the coated specimens were much lower than that of the un-coated 304. The scale spallation resistance was also dramatically improved. The phases and microstructures of the coatings and oxide scales were characterised using XRD and HRSEM. The effects of the processing parameters are discussed based on the experimental results. Further improvements in an effort to obtain more uniform coatings are also proposed.