| Flow passage components are used as the key parts of material transfer in industrial production.Its performance directly affects the efficiency and cost of industrial production.At present,high chromium cast iron is used as the main material to manufacture impeller of slurry pump and guard plate.However,it has the disadvantages of high chromium content,low toughness,poor erosion-corrosion resistance.In the process of material transmission,strong erosion and corrosion will occur to the flow passage components.Therefore,the development of new high-performance erosion-corrosion resistant materials to improve the performance of the flow passage components has become a key problem to be solved urgently.As a new wear-resistant material,Fe-B alloy has been widely paid attention because of its excellent wear resistance and impact toughness.Based on Fe-B alloy,Fe-Cr-Ni-B alloy was prepared by adding Cr and Ni elements.And,it was tested to the hardness,impact toughness and erosion-corrosion resistance of the alloy.The erosion-corrosion behavior of the three kinds of alloy was mainly studied under different impingement angles and stirring rates.The microstructure and erosion-corrosion mechanism of Fe-Cr-Ni-B alloy were investigated by means of scanning electron microscopy(SEM),X-ray diffraction(XRD)and energy dispersive spectroscopy(EDS).The main conclusions are as follows:(1)The as-cast microstructure of Fe-17Cr-0.5Ni-B alloy and Fe-17Cr-2Ni-B alloy were consisted of martensite and two kinds of borocarbides.The borocarbide at the grain boundary is M2(B,C)-type,which is in the form of the network.The morphology of M7(B,C)3-type borocarbide in the intragranular is a tiny rod-shaped and granula.The as-cast microstructure of Fe-18Cr-9Ni-B alloy consisted of austenite and M2(B,C)-type borocarbide.Three kinds of alloy after heat treatment,the matrix of Fe-17Cr-0.5Ni-B was transformed from martensite to ferrite,and a lot of granular M23(B,C)6-type borocarbide precipitated in the intragranular.It is the same to the microstructure of Fe-17Cr-2Ni-B and Fe-18Cr-9Ni-B alloys after heat treatment.(2)For three kinds of Fe-Cr-Ni-B alloy and Cr28 high chromium cast iron,the high stirring rates of slurry leads to the increase of weight loss and the decline of the erosion-corrosion resistance of four kinds of alloy.With the increase of the slurry impingement angle,the erosion-corrosion weight loss of the four alloys all increased first and then decreased,and under the test condition of 45 impingement angle,the erosion-corrosion weight loss of the four alloys all reached the maximum.Under the same erosion-corrosion test conditions,it is lower to the weight loss of three kinds of Fe-Cr-Ni-B alloys than that of Cr28 high chromium cast iron,and the weight loss of Fe-18Cr-9Ni-B alloy is the lowest and has the best erosion-corrosion resistance.(3)It is determined to the erosion-corrosion resistance of Fe-Cr-Ni-B alloy by the matrix and borocarbide.The high stirring rates of the slurry leads to erosion and corrosion damage of the matrix,resulting in the exposed borocarbide around the matrix.Under the impact of the quartz particles in the slurry,the borocarbide is broken and peeled off,leaving the borocarbide pits.The austenite matrix of Fe-18Cr-9Ni-B alloy has excellent corrosion resistance,which can effectively resist the erosion-corrosion of the slurry,and give full play to the supporting role of borocarbide,so that the borocarbide fully shows the erosion-corrosion resistance for the slurry.So the Fe-18Cr-9Ni-B alloy exhibits best erosion-corrosion resistance.The erosion-corrosion interaction weight loss ratio of Fe-18Cr-9Ni-B alloy is greater than that of pure erosion or pure corrosion,and the erosion-corrosion interaction is the key factor leading to erosion-corrosion damage of alloy.(4)The study of microstructure and erosion-corrosion resistance of Fe-Cr-Ni-B alloy can not only clarify the failure behavior of matrix and hard phase under the condition of liquid-solid two-phase erosion-corrosion,but also provide important theoretical and practical basis for the development of new erosion-corrosion resistant materials.The erosion-corrosion resistance of Fe-Cr-Ni-B alloy is better than that of traditional Cr28 high chromium cast iron,and it has potential engineering application value. |
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