Diamond is seeing increasing use in surface engineering applications because it can offer extremely desirable properties, such as high strength, high hardness, and good thermal properties. However, in terms of practical use, pure diamond has limitations due to brittleness, difficulty in processing and importantly, cost. The incorporation of diamond into the metal matrix of a thermal spray coating to produce a composite hard facing coating is investigated in this work. In this preliminary study the feasibility of spraying a diamond-metal composite, the ability to retain the diamond without excessive degradation and the associated properties of the coating in terms of hardness are reported. Synthetic and natural diamond grits were used in conjunction with nickel based hard facing powders as the matrix, to produce the composite coatings. Spraying was carried out using a standard oxy-acetylene spraying torch. The coating microstructures were then investigated using light and scanning electron microscopy and their elemental composition was probed using energy dispersive X-ray analysis. X-ray diffraction was used to identify whether diamond was retained without phase transformation to graphite and to characterise the other phases in the coatings. Macrohardness testing was also used as a preliminary measure of the quality of the coating. Preliminary results show that it is possible to produce a hard facing diamond composite coating and that there is scope to optimise the coating for the ultimate application, which, in this case, is for an oilfield drilling tool, where the coating would be subjected to extreme conditions of wear and wear corrosion. © 2003 IoM Communications Ltd.
|Number of pages||7|
|Publication status||Published - Apr 2003|