Hiroshi Takayasu

Effects of alloying elements on cavitation-erosion resistance of austenitic stainless steel deposited metals.

There are increaseing needs for the fabrication of hydraulic machineries which are used under the severe condition of cavitation. So, the anti-erosion weld deposits are usually overlaid on the position where the cavitation is likely to take place. However, there is large discrepancy that the surfacing weld deposits which has better weldability exhibit less erosion resistance. Increase in the hardness of the deposits is effective to improve its erosion resistance, while it spoils the weld-cracking avoidability of the deposits. In order to prevent the cracking of the deposits, it is necessary to increase its ductility. There should be a strong demand for the development of the surfacing weld deposits of the good combination of the erosion resistance and weldability.Investigations have been performed on the effects of the contents of carbon, manganese and nickel on the erosion loss and the elongation of the austenitic weld deposits containing 20% chromium and 7%cobalt. Results are as follows;(1) Erosion loss and its deviation increase as the nickel equivalent increases. It is necessary to limit the maximum of nickel equivalent less than 12.5% in order to assure erosion loss less than cobalt base alloy of low carbon content whose composition system is 0.06%C-19%Cr-9%Ni-15%W.(2) Elongation behaves likely to erosion loss. It is necessary to limit the minimum of nickel equivalent in order to assure the elongation more than 10%.(3) The erosion loss Cw (mg) and the elongation El(%) can be respectably estimated by the following experimental formulas. Cw=-64.6+115.60+10.1Mn+18.6Ni and El=-21.4+51.1C+2.5Mn+4.8Ni.(4) The weld deposits whose chemical composition system is 0.25%C-3%Mn-3%Ni-20%Cr-7%Co have good combination of erosion resistance and weldability.