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In this work, an inductively-coupled rf plasma reactor was utilized in the nitriding process for surface hardness improvement of aluminium-copper alloy 2011. Substrate bias at 400V was used in the pre-sputtering step to eliminate the aluminium oxide on the samples. Plasma nitriding was carried out in a N2-H2 admixture at total pressure of 1 torr. The process length was varied from 9 to 36 hours while the input rf power and substrate temperature were varied from 100 to 300 W and kept at 400 oC, respectively. A negative bias voltage up to 400 V was used in the nitriding process. Glancing incident-angle x-ray diffraction (GIXRD) results showed the hexagonal crystal structure of AlN on samples. The roughness increased slightly when the voltage increase up to 400V and was investigated by Scanning Electron Micrograph (SEM). Electron Probe Microscopy Analysis (EPMA) and Energy Dispersive X-ray Analysis (EDX) were used to detect the N atoms in specimens. Significant increases of surface hardness are observed after plasma nitriding.

Ti-W-N thin films grown on Si (100) and AISI D2 steel substrates had been deposited by a d.c. magnetron sputtering with pure Ti and W targets in a mixture of Ar and N2 plasma. The nitrogen partial pressure was varied from 0% to 9% of total gas. All Ti-W-N films were formed in solid solution with determination by x-ray diffractrogram analysis. A strong preferred orientation TiN(111) was detected. Their mechanical properties were studied using nanoindentation with Berkovich tip. An increase in hardness was observed with increasing nitrogen partial pressure. The optimum protective coating for plastic deformation was Ti-W-N film grown at 9% nitrogen partial pressure. Chemical bonding of Ti-W-N films was investigated by x-ray photoelectron spectroscopy. Binding energy analysis showed that N was mainly in TiN and W2N. The corrosion behavior was studied in variation of nitrogen partial pressure. Ti-W-N films deposited on steel at low nitrogen partial pressure showed excellent corrosion resistance in NaCl solution.

In this work, plasma nitriding of Al-6wt%Cu alloy was carried out using radio frequency inductively coupled plasma (rf-ICP). The nitrided sample was performed under various percentages of hydrogen gas mixture (25%H 2 +75%N 2 , 50%H 2 +50%N 2 , 75%H 2 +25%N 2 , and 100%N 2 ) with the input rf power of 200 W and working pressure of 0.5 torr. The plasma nitriding process time was set at 6 h. The substrate temperature was kept between 290 o C and 316 o C. The AlN hexagonal (wurtzite) crystal structures were identified by X-ray Diffraction (XRD). Electron probe micro analysis (EPMA) was carried out in order to determine the nitrogen profile. Nitrogen content in all samples was obtained in this experiment. However, only 25%H 2 with 75% nitrogen, 50%H 2 with 50%N 2 , and with 100% nitrogen was able to clearly indicate the crystal structure of AlN. The surface hardness was measured by using nanoindentation with a Berkovich indenter.