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<p class="AMSmaintext1">Thin films were deposited on SUS440 stainless steel samples by arc plasma evaporation at bias voltage range from -10 to -100 V. X-ray diffraction, optical microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, microhardness test, and electrochemical test were used to investigate the morphology and properties of the thin films. Particularly, the thin films were composed of chromium nitride (CrN, phases of CrN + Cr) and 0.76 mm thick. They were deposited with microdroplets on the samples. The surface hardness of these films reached the highest value of 1492 HV at the bias of -20 V. As the bias voltage increased, the adhesion of the CrN thin films decreased. The excessively high bias voltage of -100 V led to the delamination of the CrN thin films. The electrochemical test demonstrated that the corrosion resistance in the 3% NaCl solution of CrN coating can be improved.</p>

Thin CrAlCuN films with a composition of 21.5Cr-18.6Al-5.6Cu-54.3N (at.%) were deposited on steel substrates by the cathodic arc plasma deposition, and oxidized for up to 50 h in air. They consisted of alternating crystalline CrN/AlN nano-multilayers where Cu was incorporated. At 800 degrees C, a thin Cr2O3 layer formed. At 900 and 1000 degrees C, an outer Cr2O3 layer and an inner (α-Al2O3, Cr2O3)-mixed layer formed. Copper diffused outward to a small extent during oxidation. The film had good oxidation resistance, owing to the formation of the protective Cr2O3 and α-Al2O3.

A low carbon steel, Fe-2.25%Cr steel (ASTM T22), and Fe-2.25%Cr-1.6%W steel (ASTM T23) were aluminized by hot dipping into molten Al baths. After hot-dipping, a thin Al-rich topcoat and a thick alloy layer formed on the surface. The topcoat consisted primarily of a thin Al layer that contained a small amount of Fe, whereas the alloy layer consisted of Al-Fe intermetallics such as Al 5 Fe 2 and AlFe. Cr, Mo, and W in T22 and T23 steels reduced the thickness of the topcoat and the alloy layer, and flattened the reaction front of the aluminized layer, when compared to the low carbon steel.