Enhancing the Cavitation Erosion Resistance of 304 Stainless Steel by Laser Surface Alloying with Molybdenum

Abstract

Type 304 stainless steel is the most versatile and widely used austenitic stainless steel, it accounts for more than 50% of all stainless steel produced. It is commonly used in liquid handling equipment, house hold utensils and lot of applications in almost every industry. However, poor surface properties in terms of wear resistance, due to its low hardness made it susceptible to cavitation erosion, which is a usual mode of degradation of engineering parts in contact with fast-flowing or vibrating liquids. This work is an attempt to improve the cavitation erosion resistance of 304 stainless steel by laser surface alloying with Molybdenum (Mo). This was made possible by using a 2kW continuous wave Nd-YAG laser. The alloying powder was placed in advance on the surface of the substrate by pasting to a thickness of 0.1mm, followed by laser beam scanning at an optimal speed of 20 mm/s and 30 mm/s (each at a beam diameter of 3mm) and a laser power of 1.2kW, in order to achieve surface alloying and modified surfaces were obtained by 50% overlapping of adjacent tracks. The microstructure and composition of modified layer were also studied for more insights. Ultrasonic induced vibrator tester was used to carry out cavitation erosion test. Cavitation erosion resistance (Re) was observed to have increased with the Mo content in the alloyed layer, the Re of the specimens modified with Mo was improved by a factor of 1.4 (for v = 20 mm/s) and 1.5 (for v = 30 mm/s), when compared with that of the as-received 304 stainless steel substrates.