Machinability of Duplex and Super Duplex Stainless Steels

Sammanfattning

This master thesis aims at investigating the machinability of duplex, grade 1.4462and super duplex stainless steels, grade 1.4410 from a tool wear perspective, assessingfactors such as cutting forces, chip thickness, and wear evolution. To investigateit, two types of tests were used: orthogonal and longitudinal with constant spiralcutting length. In orthogonal cutting tests, acquired force measurements, contactlengths, and chip thicknesses were studied. For longitudinal tests, forces and toolwear patterns were analysed when machining stainless steels using di!erent toolgrades. The wear formation was investigated using stereo optical microscopy, ScanningElectron Microscopy, and Energy Dispersive Spectroscopy.Orthogonal testing showed correlation between average forces, chip thickness andtool-chip contact length. Significant di!erences in tool-chip contact length betweengrades GC2220 and GC2025 were observed. Overall super duplex stainless steelmachining resulted in higher average cutting forces, lower average chip thickness,and lower contact length as compared to those of the duplex stainless steel.Regarding the cutting tool wear, there is a noticeable variation in type and dimensionof wear for di!erent grades. The most frequently occurring wear types were: notchwear, built-up-edge formation and crater wear. There is also a di!erence betweenwear formation for duplex and super duplex stainless steel, where both size andlocalization varied, while types of wear remained similar. Among the cutting toolgrades GC1205 had the lowest wear and cutting forces, suggesting potential forfuture implementation of superalloy-intended tools for these materials. The overallflank wear was higher when machining super duplex stainless steel