| Bearings as one of the essential components of high-end equipment has been widely used in different manufacturing industries like aerospace,rail transit,and marine equipment.GCr15 steel ball is one of the most common rolling equipment in bearing industry,but 80% of bearing failures is because of it as it is subjected to highly concentrated stress distribution and large energy gradient difference during the operations,resulting in elastoplastic deformation,transient fracture,friction and wear,etc.The wear resistance of GCr15 still needs to be improved because the main failure modes of GCr15 steel ball are contact fatigue failure and wear failure.In this study,a new theory of titanium-rich strengthening processing for GCr15 steel ball would be examined by theoretical analysis,numerical simulation,and experimental research,which including the orthogonal experimental method to reveal the influences of various factors of titanium-rich strengthening process on the wear resistance of GCr15 steel balls,aiming to seek the best process parameters to obtain the best resistance of GCr15 steel balls.The findings at below:(1)The surface strengthening technologies such as strengthening grinding technology,steel ball surface strengthening technology and mechanical alloying technology are studied.The collision stress theory,elastic-plastic deformation theory and Ti element coverage theory are deduced,and the Ti element diffusion theory is established.(2)The motion model of titanium rich strengthening machining of steel ball is established.Through edem discrete element numerical simulation,the particle trajectory and impact collision law are analyzed,and the inner wall structure of ball milling tank is optimized.(3)Through the titanium rich strengthening processing test of GCr15 steel ball,the thickness of Ti diffusion layer,Ti content,grain size,hardness and other microstructure of the processed sample were measured and observed.The results show that after processing,a certain thickness of Ti diffusion layer will be formed on the surface of GCr15 steel ball,the gradient of Ti content layer decreases,the grain is refined and the hardness is improved.The thickness of Ti diffusion layer of test group 9 is up to 3.74 ?m.1 from the diffusion layer surface of the sample ? The content of Ti in M is up to 15.43%,The minimum average grain size is 15.41 ?m,Off surface 20 ?m The Vickers microhardness at M is up to 893.8HV.(4)The friction and wear tests of GCr15 steel balls were carried out,and the friction coefficient and wear width of GCr15 steel balls were analyzed.The results show that the wear resistance of GCr15 steel balls can be improved by titanium enriched processing.Under dry friction,the friction coefficient of test group no.9 was as low as 0.545,33.54% lower than that of blank group,and the friction mark width was as low as 884.6?m,19.54% lower than that of blank group.Under the condition of oil lubrication,the friction coefficient of test sample no.9 reached 0.1765,decreased by 15.75%,and the width of wear mark was 259.2?m,decreased by 37.41%.It has the best wear resistance.The Ti atom introduced into the processed sample can inhibit the movement of the material,and the grain of the processed sample is refined and the hardness is improved,thus improving the wear resistance of the material. |
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