|KONIECZNY Marek||Kielce University of Technology|
|Spoluautoři SZWED Bartłomiej, KARDYNAŁ Igor|
Composite gamma-Ni+gamma’ coatings on an iron substrate with a nickel interlayer were developed by the conversion of electrodeposited Ni+Al films with dispersed Al particles in Ni matrix. The conversion was made by vacuum annealing at 900 oC for 3 h without and under uniaxial pressure of 1 MPa to obtain porous and full-density coatings, respectively. The cyclic-oxidation resistance of both types of produced coatings at 1000 oC was compared. It was noticed the detrimental effect of porosity on the oxidation resistance of gamma-Ni+gamma’ composite coatings. SEM/EDS and XRD characterisation of nonporous coatings showed that during oxidation a protective continuous Al2O3 layer is formed below a zone of NiAl2O4 spinel. The Al2O3 layer in porous gamma-Ni+gamma’ coatings was identified as discontinuous and therefore not fully-protective. After 100 h at 1000 oC a mass gain for nonporous gamma-Ni+gamma’ coatings was about 7 times lesser than for nickel coating.