effect of temperature on corrosion of cermets alloy
EFFECT OF TEMPERATURE ON CORROSION OF CERMETS ALLOY
ABSTRACT
Tungsten carbides (WC) are widely used as wear resistant components such as seal, valves, rings, nozzle and bearings. But in some processing operations, the environment necessarily includes severe corrosion or extremes of temperatures. In this research, commercially cobalt tungsten carbide (WC-6%Co) and nickel tungsten carbide (WC-9%Ni) was examined in seawater (3.5% salinity) to know the effect of temperature on corrosion for both of this materials. Other than that, changes on the surface microstructure before and after the corrosion attack also been observed. Then, the corrosion attack between WC-6%Co and WC-9%Ni be compared in terms of electrochemistry, mechanical properties and microstructure. The experiment were performed at four different temperatures which is 20̊C, 40̊C, 60̊C and 80̊C. Tafel plot and linear polarization graph are used to determine the corrosion rate of WC-6%Co and WC-9%Ni. The results of Tafel plot show that WC-9%Ni is better in corrosion resistance than WC-6%Co. It is because WC-9%Ni has lower value of Icorr than WC-6%Co. The corrosion rate for both of materials also increased when temperature increase in an almost linear manner. That was same with the value of Icorr which is proportional to temperature, as the temperature increase, the Icorr value also increased. Microstructure study that been observed by using SEM show that no pitting corrosion occur for both material. Hardness for both materials had been test by using Rockwell HRA. This result shows that both materials’ hardness is decreases after corrosion attack.
Keywords: WC-6%Co, WC-9%Ni, seawater (3.5% salinity), corrosion
1.0 INTRODUCTION
.
The definition of a cermets material is the combination of a metal to a nonmetal, which is ceramic (cer) and metallic (met) materials [1]. It is the addition of the metallic binder such as cobalt (Co) or nickel (Ni) that makes the cemented carbide
ABSTRACT
Tungsten carbides (WC) are widely used as wear resistant components such as seal, valves, rings, nozzle and bearings. But in some processing operations, the environment necessarily includes severe corrosion or extremes of temperatures. In this research, commercially cobalt tungsten carbide (WC-6%Co) and nickel tungsten carbide (WC-9%Ni) was examined in seawater (3.5% salinity) to know the effect of temperature on corrosion for both of this materials. Other than that, changes on the surface microstructure before and after the corrosion attack also been observed. Then, the corrosion attack between WC-6%Co and WC-9%Ni be compared in terms of electrochemistry, mechanical properties and microstructure. The experiment were performed at four different temperatures which is 20̊C, 40̊C, 60̊C and 80̊C. Tafel plot and linear polarization graph are used to determine the corrosion rate of WC-6%Co and WC-9%Ni. The results of Tafel plot show that WC-9%Ni is better in corrosion resistance than WC-6%Co. It is because WC-9%Ni has lower value of Icorr than WC-6%Co. The corrosion rate for both of materials also increased when temperature increase in an almost linear manner. That was same with the value of Icorr which is proportional to temperature, as the temperature increase, the Icorr value also increased. Microstructure study that been observed by using SEM show that no pitting corrosion occur for both material. Hardness for both materials had been test by using Rockwell HRA. This result shows that both materials’ hardness is decreases after corrosion attack.
Keywords: WC-6%Co, WC-9%Ni, seawater (3.5% salinity), corrosion
1.0 INTRODUCTION
.
The definition of a cermets material is the combination of a metal to a nonmetal, which is ceramic (cer) and metallic (met) materials [1]. It is the addition of the metallic binder such as cobalt (Co) or nickel (Ni) that makes the cemented carbide
References: 1. The designer’s guide to tungsten carbide, general carbide federation, Chapter 1, 2009 2 3. Journal, Sutha Sutthiruangwong and Gregor Mori (2003) 4 7. Robert Baboian, Corrosion test and standards, 2nd edition, ASTM manual series, 2005 8 9. R. Weinsten Revie, Corrosion inspection and monitoring, John Willey & sons, 2007, page 23 10 11. J. J Zuckerman, Inorganic and reactions method, VCH publisher, 1988 12