Effect of Deposition Time on In Situ Thickness

The basic Brophy and Ingraham technique was studied by several other authors. Bayer and Trivedi found that the effectiveness of the technique depended more on the nature of the coating than on its thickness, and that retained moisture in the electroplate was essential for effective conversion. They recommended a current density of 21.5 A/m for 5 minutes to produce a coating thickness of 1.25 to 2.5 tjm. Nishimura and co-workers found that the presence of air or water or both in the conversion gas improved the wear life. Table 9.5 compares the properties of the in situ films with those of burnished and sputtered films, and shows superior wear life for the in situ films. Their friction results were curious, in that they found that the initial films which were formed gave low friction in air or nitrogen but not in vacuum. Low friction in vacuum was obtained when the initial product was heated in vacuum to 400°C. 

Film Type Film Friction Wear Life, Wear Life/ 

Test conditions 440C ball/440C disc, Ikgf, 1.5m/s, dry air 

X-Ray diffraction examination and electron probe microanalysis showed that the initial film was amorphous and contained an excess of sulphur. When the film was heated in vacuum at 400°C for one hour, the excess of sulphur decreased, and the X-ray diffraction pattern showed peaks possibly indicating the presence of molybdenum disulphide crystals. They inferred that the excess of sulphur initially 

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