Effect Of Laser Remelting On Microstructure And Performance Of Ultra High Chromium And High Carbon Steel

In this paper,the surface of 1.5%C-40%Cr ultra high chromium and high carbon duplex steel was treated by laser remelting to solve the cracking and precipitation during casting?phase,coarse grain and other casting problems.At the same time,with the rapid melting and solidification characteristics of laser surface treatment,solid solution strengthening and fine grain strengthening structures are obtained,so as to improve the wear resistance and corrosion resistance of metal surface.First,the surface of investment casting ultra high chromium and high carbon duplex steel was treated by single pass laser remelting.On this basis,the multi-channel laser remelting experiment was carried out.The morphology,roughness,hardness and microstructure of remelting layer with different lap ratio were studied.The electrochemical corrosion properties,wear resistance under dry friction and water lubrication of the original and remelting layers were compared and analyzed.The experimental results show that:(1)Single pass laser remelting of ultra high chromium and high carbon duplex steel was carried out with different laser power and scanning speed.It is found that the laser remelting experiment is more suitable when the laser power is 1750W and the scanning speed is100mm/min.The ideal single pass melting layer is obtained,the hardness of the substrate is obviously improved,the surface quality is better and the cracks are least.(2)The phase composition of the ultra high chromium and high carbon duplex steel before and after laser remelting is the same????M₂₃C₆three phase.The cross section of the remelting layer can be roughly divided into transition zone,columnar crystal zone,dendrite zone and equiaxed crystal zone.The microstructure distribution of the original state is similar to that of the remelted layer.The original ultra high chromium high carbon steel is composed of massive ferrite,network and short rod carbide and austenite eutectic.The microstructure of ultra high chromium high carbon steel by laser remelting is composed of ferrite dendrite,network carbide and austenite eutectic.The difference is that the microstructure of the remelting layer is finer.(3)Under the dry friction condition of ball disc wear tester with rotation speed of 0.4m/s,the wear resistance of original state is better under low load(2N),and the wear resistance of ultra high chromium and high carbon duplex steel is obviously improved by laser remelting under high load(4?8N).Under the condition of water lubrication,the load is 500N and the sliding speed is 2m/s,both the original state and the remelting layer show abrasive wear.But the friction coefficient of the remelting layer is smaller,the wear mark is shallower and the specific wear rate is smaller.(4)Electrochemical experiments show that the self corrosion potential of the remelting layer is lower,the passivation phenomenon is more obvious,the passivation current density is10^-6A/cm²,the capacitive arc diameter is larger,the passivation film resistance is larger,and the corrosion resistance is improved.The results show that the passive film has good time stability.200m V is the best film potential.The passivation film has the largest resistance,the lowest corrosion rate and the best corrosion resistance.(5)According to the above analysis,when the laser power is 1750W and the scanning speed is 100 mm/min.Ultra high chromium and high carbon duplex steel was treated by laser remelting with lap ratio of 16.7%.The surface remelting layer with finer microstructure and higher hardness was obtained.The wear resistance and corrosion resistance of ultra high chromium and high carbon duplex steel were improved by laser remelting...