EFFECT OF THERMAL CYCLING ON SLURRY EROSIVE BEHAVIOUR OF MEDIUM CARBON LOW ALLOY STEEL

Abstract

Slurry erosive wear is defined as the phenomenon of material removal from the surface by the impact of solid particle flowing in fluid at certain velocity and angle. Slurry erosion is important in various engineering applications such as oil and gas industry, pipeline systems, pumps, hydraulic machinery, etc. So, improving the performance of medium carbon low alloy steel which is mostly used in above said engineering applications leads to economic development of any country. Steel microstructure, which directly influences its strength, hardness and toughness, plays an important role in determining the wear rate. The objective of this project is to study the effect of thermal cycling on slurry erosion behaviour of 0.43 C wt. % low alloy steel. Thermal cycling is done on spheroidized, annealed and normalized medium carbon low alloy steel and cycling effect on different initial morphology is studied. Thermal cycling consists of alternate heating and cooling at 50ºC above and below A3 temperature (852ºC) with holding time of 3 min. at both temperatures. Heating and cooling rate for thermal cycling is 5ºC/s. Thermal cycling results in variety of microstructures and mechanical properties. The slurry erosion tests were performed on slurry erosion pot test apparatus using silica sand particles (size – 212 to 300μm) as erodent. Weight loss was calculated after every 3 hr. time interval and total test time was 24 hr. The experimental findings reveal that thermal cycling improves slurry erosion resistance. It was found that cumulative weight loss shows direct relationship with hardness with respect to similar morphology materials. Minimum weight loss is observed in case of two time thermal cycled annealed material (57% decrement w.r.t. as-received spheroidized material). The microstructures and worn out surfaces were analyzed by optical microscopy and field emission scanning electron microscopy.