MECHANICAL PROPERTIES OF THE Fe-Al-Nb COATING BY DOUBLE GLOW PLASMA SURFACE METALLURGY

Abstract

The Q235 steel was covered by Fe–Al–Nb alloyed coating to improve the mechanical properties of the Q235 steel. This double glow plasma surface metallurgy (DGPSM) surface modification technique was carried out at 1023[Formula: see text]K and pressure of 38[Formula: see text]Pa for 4.5[Formula: see text]h. The surface morphology represented the typical Volmer–Weber mode, an island structure which was accumulated by numerous small particles, and most of the angles formed between three islands were about 120[Formula: see text] where there was no appreciable defect. Meanwhile, in the cross-sectional morphology of the Fe–Al–Nb coating, there was a deposition layer, a diffusion layer and two transition regions between the different adjacent interfaces, and the coating approximate 17[Formula: see text][Formula: see text]m was found to be metallurgically adhered to the Q235 steel. The basic mechanical properties of the Fe–Al–Nb coating and Q235 steel including the hardness, elastic modulus and friction performance were measured and compared. The results showed that the formation of Fe3Al, FeAl, and Fe2Nb intermetallic compounds and Nb carbides in the coating can enhance the mechanical properties of the treated sample. The nanoindentation tests indicated that the hardness and elastic modulus of Fe–Al–Nb coating were 8.08[Formula: see text]GPa and 260.03[Formula: see text]GPa which were much higher than Q235 steel. The sliding friction tests showed that Fe–Al–Nb coating significantly improved the friction performance of Q235 steel at the speed of 300, 600 and 900[Formula: see text]rpm with load 320[Formula: see text]g for 15[Formula: see text]min.