Microstructure and Properties of FeAl Coatings Prepared by APS, LPPS and HVOF

Abstract

Abstract The FeAl intermetallic compound coatings were sprayed by low pressure plasma spraying (LPPS), air plasma spraying (APS) and high velocity oxy-fuel spraying (HVOF). The influence of three kinds of thermal spraying processes on the microstructure, microhardness, elastic modulus and fracture toughness of coatings were investigated. The results showed that the APS and HVOF coatings exhibited similar microhardness, about 540HV0.3, which is much lower than that of LPPS coatings, 860HV0.3. The elastic modulus measured for APS, HVOF and LPPS coatings using Knoop indentation were 96, 84, 176GPa, respectively. The APS coatings were also observed to have lower elastic modulus values in the in-plane direction than those in the perpendicular direction, as a result of microcracks scattered within the coatings. In fracture toughness tests, the LPPS coatings revealed the lowest fracture toughness, as compared with other two spraying processes, indicating low porosity and crack levels are related to low fracture toughness. From these results, it appeared that potential improvements to certain mechanical properties can be achieved using low pressure plasma spraying process.