Authors: Xiao Bin Zhang, Xia Chang, Tao Wei, Chang Sheng Liu
Abstract: A Ni-based alloy NiCrSiB laser cladding layer was made on the surface of CrNiMo stainless steel specimens using NiCrSiB powder. Cavitation erosion behavior of the laser cladding layer and the CrNiMo stainless steel was investigated by ultrasonic vibration cavitation erosion equipment The results shown that laser cladding layer has dense microstructure and has metallurgical combination with CrNiMo stainless steel substrate. Because of impact effect of cavities collapse, micro-cracks caused material broke off from samples. NiCrSiB laser cladding layer have better micro-crack propagate resistance property than CrNiMo stainless steel.Laser cladding layer has better cavitation resistance properties because of strengthening effect by precipitated phases such as M23[CB]6、CrB、CrSi、Fe2B、B4C and work hardening effect during cavitation erosion process.
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Authors: Ashish Selokar, D.B. Goel, Ujjwal Prakash
Abstract: Abstract: Hydroturbine blades in hydroelectric power plants are subjected to erosion. Currently these blades are made of 13/4 martensitic stainless steel (ASTM grade A743). This steel suffers from several maintenance and welding related problems. Nitronic steels are being considered as an alternative to martensitic stainless steels since they have good weldability. In present work, erosive behaviour of 13/4 Martensitic and Nitrogen alloyed austenitic stainless steel (23/8N steel) has been studied. Cavitation erosion tests were carried out in distilled water at 20 KHz frequency at constant amplitude. Microstructure of eroded surface, mechanical properties and erosion rate were characterized. It was observed that 23/8N steel possesses excellent resistance to erosion in comparison to 13/4 martensitic steels. 23/8N steel showed good hardness coupled with high tensile toughness and work hardening ability, leading to improved erosion resistance.
554
Authors: Wei Fu Wang, Jian Zhou Xie, Liu Yi Huang, Fang Fang Zhang
Abstract: In order to compare the performances of two typical laser coatings used in turbine blades, the Ti-N coatings of Ti6Al4V alloy and solution-aging coatings of 17-4PH alloy were fabricated by laser treatment with optimized parameters, respectively. The formation mechanisms and performances are comparative investigated by SEM, TEM and cavitation erosion tester. The results show that the Ti-N coatings are mainly reinforced by Ti2N and α′ martensite. For 17-4PH samples, the TEM observation displays that the ε-Cu particles, which are in the size of 2-5 nm and disperse homogeneously in the martensite matrix, are the main reinforcing phases. Both the 17-4PH samples and the Ti6Al4V samples are reinforced homogeneously. Comparative Analysis indicates that the hardness of the Ti-N coatings on Ti6Al4V substrate is lower than that of solution-aging samples (on 17-4PH). However, the cavitation erosion resistance of the Ti-N coatings are better than that of solution-aging samples, which implies that the titanium alloy with Ti-N coatings are well candidate to instead of 17-4PH steel for the application in turbine blades.
193
Authors: C.H. Zhang, Y.F. Jia, M. Guan, C.L. Wu, J.Z. Tan, S. Zhang
Abstract: Fe-based alloy modified layers were prepared on 304 stainless steels by high-energy pulse laser-like cold welding cladding technique. The microstructure, composition and phase constituents of the cladding layers were analyzed using SEM, EDS and XRD, respectively. The microhardness, friction-wear and cavitation erosion resistance were also investigated using microhardness tester, pin-on-disk wear-testing machine and ultrasonic vibrator. Experimental results showed that Fe-based alloy modified layer was mainly composed of α-Fe matrix phase and skeleton-like Cr23C6, Cr7C3 carbide reinforced phase, which was dispersively distributed into α-Fe matrix. The microhardness and friction coefficients of Fe-based alloy modified layer were 600HV and 0.4, respectively, indicating an improved wear resistance. The weight loss rate and average erosion depth of the modified layer was 1/5 and 1/10 that of 304 stainless steel in 3.5% NaCl solution after 5-h cavitation erosion test, respectively. The erosion crater depth of the modified layer was uniform, indicating that the cavitation erosion resistance of the modified layer was much better than that of the 304 stainless steel.
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