| In this paper, WC reinforced Ni-base alloy composite coating was prepared on the 45 steel by vacuum fusion sintering. Different content of WC(10%, 20%, 30%, 40%wt) was added into the nickel base alloy, then fused at 1200℃, 1225℃, 1250℃, 1275℃, respectively, to make different coating samples; The microstructure of the coatings was observed by OM, XRD, SEM. The hardness of the coatings was examined by micro-hardness and rockwell hardness testers. The wear-resistance properties and corrosion-resistance of the samples were tested by wear resistance machine and abrasion tester, respectively. The technological parameters were optimized based on the above experiments. The way how WC dissolved into liquid was analyzed. Proper technology for heating process was majorized.According the results: VFS samples mainly contain cladding layer, transition layer and base metal. In cladding layer, binding phase mainly had austenite(Fe Ni,Ni2.9Cr0.7Fe0.36), strengthening phase mainly had WC and W2 C. In addition, Borides, Silicide, strip phase Carbide(Cr7C3,(Cr, Fe)7C3), and composite compounds also exist in the cladding layer. The transition layer has better toughness and corrosion-resistance, for which the compositions chiefly concluded Fe, Ni and Cr. The existence of transition layer indicated that cladding layer combined with base steel hardly. The microstructure of the base steel near cladding layer mainly consisted of pearlite, and the microstructure of the base steel in other areas is mainly composed of pearlite and ferrite.When amount of WC in cladding layer is less than 20%, dense cladding layer was obtained at different fusion temperature, however, its had lower wear-resistance property. If the content of WC is larger than 30% and fusion temperature was low, the formability of cladding layer was poor, for which had a lot of pores and concaves, the coating became porous, the surface was uneven. With the temperature increasing, cladding layer became denser. But Rockwell hardness and wear-resistance property would get lower as the fusion temperature rised owing to the decomposition of WC. Therefore, 1225℃ was the proper fusion temperature.At 1225℃, when WC content was less than 30%, with the content of WC increasing, wear-resistance of coatings improved. When content of WC is 30%, the wear-resistance of cladding layer was 6 times as base steels. and WC distribute in claddying layer uniformly, If continually increasing WC into the Ni base alloy, much more pores would be appeared in cladding layers. The binder phase could not keep WC steady and leaded to a low wear-resistance property. corrosion-resistance property of each cladding coatings was 10 times more than that of base steel. The optimized amount of WC was about 30%.Normalizing, water quenching and oil quenching had great influence on base steel, while had little influence on coatings. Quenching led to crack emerging near transition layer. The crack had a bad effect on bond strength, therefore, normalization is chosen at last.The optimized fusion temperature and adding amount of WC are 1225℃ and 30%(wt.%). The wear-resistance and corrosion-resistance properties of the cladding layer obtained at above process were 6 and 10 times, respectively, more than base metal. The rockwell hardness was about 40 HRC, cladding layers could reinforce the base steel efficiently. |
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