A Study On Frictional And Wear Properties Of Drilling Joints Thread Based On Sulfurizing Technology

Lubricant and lubricational technology are developing with the progress of science. The research on solid lubrication is good for developing the conventional theory of tribology. The friction and wear problems of material can be solved more effectively by using solid lubrication technology, and huge economic, environment and society benefits can also be produced. FeS is a typical solid lubricant. It can reduce the friction and wear effectively because of its porous structure with low hardness, shear strength and good lubricating property. So the FeS has good prospect of application.In order to improve the frictional properties of drilling joints, FeS solid lubricant was used in the drilling and exploring machinery parts. Ion sulfurization technique was utilized with the conventional nitriding process to treat the 35CrMo steel to prepare the sulfur-nitriding composite layer. The ion-sulfurizing process under low temperature was investigated by plasma heat-treating facility. The frictional properties of nitriding layer and sulfur-nitriding composite layer on 35CrMo steel surface under different lubrication was investigated by GWL-1000 and MM-200 friction and wear tester, and the practical using effect of drilling pipe joint thread treated by sulfur-nitriding was also studied. Microstructure analysis instruments were adopted to analyze the morphologies, structure, element valence state, element distribution and mechanical property of original and worn sulfur-nitriding layers, and the working mechanism of composite layer was discussed as well. The corrosion resistances of composite layers under different corrosive conditions were studied by electrochemical instrument. To optimize the design of drilling joints, finite element analysis way was used to research the variations of surface force.The result shows that the sulfur-nitriding layer had been formed on the 35CrMo steel surface. The composite layer possess has better anti-wear performance than that of single nitriding layer under different lubrication conditions. The service life of the practical parts can be improved effectively by using sulfur-nitriding treatment technology. The corrosion resistance of composite layer is better than the nitrizing layer in acidic corrosion condition. According the finite element analysis, the hardness of female thread surface and the root of male thread should be enhanced by surface strengthening way, and the transition region should be smoother by better processing.Experimental results and theoretical researches in this dissertation show that sulfur-nitriding 35CrMo steel has good tribological characteristics. FeS solid lubricant illustrates an optimistic prospect of application in drilling and exploring.