The Coating Design In Nodular Cast Iron Substrate Surface And Performance Analysis

As a substitute material for steel, ductile iron is widely used in processing and manufacturing of mechanical equipment and parts for its excellent mechanical performance. It is an effective method to improve the performance of mechanical equipment and parts by producing a variety of functional coating in nodular ductile cast iron substrate surface. Five kind models of wear and corrosion resistant coating in the surface of nodular cast iron is established in this paper. And the coating performance of thermal stress and corrosion resistance is studied through the ANSYS finite element simulation and corrosion experiment of acid and alkali. The main research results are as follows.The main factors which affecting the interface thermal stress are coating thickness, direction of heat transfer, interface shape and coating material. The thermal stress simulation analysis of C-276 coating which thickness is in 0.02-0.2(mm) and PFA+C-276 coating model found that within the thickness scope of 0.08-0.12 (mm), interface thermal stress performance of Hastelloy C-276 alloy coating is excellent. The coating thermal stress in the condition of heat transfer direction perpendicular to coating surface is higher than heat transfer direction parallel to coating surface. Coating thickness is 0.20(mm), interface stress in the condition of longitudinal heat transfer is an order of magnitude higher than that of horizontal. The main structure design parameters of PFA+C-276 double coating membrane is the best thickness ratio of surface and bottom layer in 0.176-0.33 and best total thickness of surface and bottom in 0.1-0.15 (mm).In the research of thermal stress performance of coating in different frequencies sinusoidal curve and the screw surface found that with the increase of frequency, the stress concentration and fluctuation is more obvious in peaks and troughs. In the addendum circle edge and dedendum circle corner of the screw surface, the axial and radial stress respectively occur jumps and mutations phenomenon, maximum stress is 4-5 times for the average stress.Under the same condition of temperature field, the different coating and substrate material physical properties is the main factor which influences the interface thermal stress. Thermal stress properties is commanded by the difference between coating and substrate thermal expansion coefficients. The difference value is timing, performance for tensile stress; the difference value is negative, performance for compressive stress; with the increase of difference, thermal stress increase; difference increase every 10-6 /℃,thermal stress increase 6-7 (MPa).The coating samples in nodular cast iron substrate surface were prepared by thermal spraying and vacuum magnetron sputtering deposition technology. Through the three groups of corrosion experiment found that the coating and substrate all have excellent performance of alkali corrosion resistance and the corrosion of HCl is slight stronger to that of H2SO4. The thick 50Ni-33P-10Cr-7Fe coating produced by thermal spraying technology has excellent resistance to strong acid corrosion and the average corrosion amount of 10%H2SO4,2%H2SO4 and 2%HCL solution for the coating respectively is 2.1 × 10-3g/h,1.54 × 10-4g/h and 2.08 × 10-4g/h.