| dc.description.abstract | In the oil and gas industry, components used in the drill mud handling system suffer from erosive wear. Drill mud containing a fairly large fraction of sand moving at high speed, creates harsh conditions with respect to erosion. Cemented carbides are being used as coating to obviate wear caused by erosion and abrasion in the most exposed and critical components. However, in some cases when selecting a coating material, the erosive wear resistance is not the only property of concern. Lyng Drilling, a Slumberger company, has developed a new type of nickel coating with certain properties to be used in drilling mud systems. The coating has proved to meet its requirements, but wears out rather fast due to erosion. To retain the desired properties and at the same time increase erosive wear resistance, reinforcement of the nickel coating with diamond particles has been proposed as a solution.This study mainly concerned erosion of diamond composite coatings, where the aim was to quantify the erosion dependence on diamond concentration and angle of impact. In addition, the effect of the size ratio between hard particles in the coating and the erodent were going to be investigated. This was not carried out as the erosion rig used was not capable of transporting fine grained sand. Up to this date, more research has been conducted on erosion behavior of cemented tungsten carbides than for diamond composites. Two cemented tungsten carbide materials were therefore included in the test program to compare the erosion behavior with a more familiar composite material.Nickel-diamond coatings containing 31, 38 and 43 vol.% 36 to 38 micro meter large diamond particles were tested at 15 and 30 degrees impact angle. A new slurry jet erosion test rig, where the erodent was applied to the water jet stream by compressed air, was used to perform erosion test of the materials. During the test program some essential weaknesses with the concept were discovered, which in turn have limited the results achieved from this project. However, the results from the current work indicate that erosion decreases with a higher concentration of diamond particles. Also, less erosion was seen at 15 degrees impact angle, than for 30 degrees. Investigation of the eroded surfaces in Scanning Electron Microscope (SEM) showed that the diamond particles developed comet tails of binder material behind it. Longer comet tails were seen for 15 degrees than for 30 degrees, which is believed to be the reason for the brittle characteristic with respect to angle. The mechanical properties of the new materials had not been investigated in detail at the start of this project. A lot of effort has therefore been put into characterizing the materials. Methods and results from experiments performed to decide the volume fraction of hard particles in the composites, the hardness, roughness and the adhesion to the substrate material are presented. In addition, microscopy by Infinite Focus Microscope (IFM) and SEM of the materials is described. | nb_NO |
