Production and structure of electrolytic composite layers containing titanium in Ni-Mo alloy matrix
Jolanta Niedbała Uniwersytet Śląski, Instytut Fizyki i Chemii Metali, ul. Bankowa 12, 40-007 Katowice
Annals 3 No. 6, 2003 pages 53-57
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abstract The composite layers on a base of Ni-Mo alloy containing titanium were obtained by electrodeposition from the citrate bath containing a suspension of titanium powder. The process was carried out under galvanostatic conditions. For comparison Ni- Mo alloys were also obtained under the same conditions from the citrate solution without Ti powder and comparative tests were conducted on them. The rate of layers deposition was estimated, and their chemical composition was determined using X-ray fluorescence spectroscopy method. It was stated, that the content of molybdenum in Ni-Mo alloys varies in the range from 20.7 (j = 100 mA/cm2) to 30.5% (j = 250 mA/cm2). Further increase in deposition current density to 300 mA/cm2 causes a slight decrease in Mo content in the layers to 28.1%. For Ni-Mo+Ti layers the content of Mo lies between the limits 5.7% (j = 100 mA/cm2) to 24.6% (j = 200 mA/cm2). So, it should be stated, that incorporation of Ti powder into the galvanic bath causes a decrease in the Mo content in alloy matrix. Moreover, it could be ascertained, that the presence of titanium powder in galvanic bath inhibits the process of induced electrodeposition of molybdenium with nickel. It was stated that Ni-Mo+Ti composite layers deposited in the range of deposition current density from 100 to 300 mA/cm2 contain from 5.7 to 24.6% of Mo and from 9.9 to 66.7% of Ti. Structural investigations were conducted by X-ray diffraction method. The phase composition of Ni-Mo alloys and Ni-Mo+Ti composite layers before and after thermal treatment at a temperature of 1100oC was determined. It was ascertained that electrodeposited Ni-Mo alloys are characterized by nanocrystalline strucure whereas Ni-Mo+Ti composite layers have an crystalline Ti phase built into the nanocrystalline Ni-Mo matrix. It was stated, that thermal treatment changes the phase composition of Ni-Mo alloys and Ni-Mo+Ti composite layers. X-ray diffractograms of the alloys and composite layers show the reflects coming from intermetallic compounds. In the Ni-Mo alloys the presence of Ni4Mo was stated and in Ni-Mo+Ti composite layers additionaly NiTi and Ni3Ti phases are present. The presence of these compounds conformed the fact of nanocrystalline Ni-Mo matrix crystallization proceeding during thermal treatment of the layers. In Ni-Mo+Ti layers the chemical reaction between Ni-Mo matrix and incorporated Ti powder occurs. Key words: Ni-Mo alloys, titanium, electrolytic composite layers, electrodeposition