The effect of process parameters on the plasma carbon diffusion treatment of stainless steels at low pressure

The need for a hard wearing material with acceptable corrosion performance for use in various applications has led to the preliminary investigation of plasma carbon diffusion treatment of stainless steels at low temperatures. The types studied were AISI 316, 321, 431 and 440C. Components were plasma carburized at 350°C, using a thermionically enhanced low pressure (10−6.5 υbar) d.c. triode configuration. The effects of negative workpiece voltages in the range of 50–150 V on composition, hardness profile, case depth and uniformity of layer thickness are reported. Various surface analytical and depth profiling techniques have been used to determine these properties. X-ray diffraction was employed to determine crystallographic structure, grain size and lattice microstrain. The effect of sputter pre-cleaning in argon or argon/hydrogen is also reported. The performance of the coatings has been evaluated in wet slurry abrasive wheel tests, which demonstrate an improvement in wear resistance.