Exploring residual stress analysis in the machining of hypoeutectic high chromium white cast iron alloys through the hole-drilling method

Abstract High chromium white cast irons (HCWCIs), ASTM A352, Type A and Class III, i.e., 25 % Cr iron in as-cast condition consists of proeutectic austenite ( γ -Fe), transformed martensite ( α -Fe) and discontinuous Cr-rich, i.e., M 7 C 3 / (Cr, Fe) 7 C 3 type of carbides, which are hard and brittle in nature. Fully annealed thermal treatment was performed to improve iron’s machinability leading to fully pearlitic matrix with minor retained γ -Fe content. Eutectic (Cr, Fe) 7 C 3 type of carbides are not affected by heat treatment processes. Resulting from corresponding manufacturing process, the magnitude and distribution of residual stresses (RSs) in as-cast and after machining were measured using hole-drilling method (HDM), as they are known to be harmful to corrosion and fatigue resistance. Furthermore, general metallurgical material characterisation was performed in as-cast and heat-treated conditions. As a result, this study revealed hardness variation, 547 and 555BHN in as-cast as compared to 327BHN in heat-treated condition. Furnace and actual cast component chemical analysis revealed a slight variation, especially between carbon (C) and chromium (Cr). Furthermore, eutectic type of carbides and precipitated secondary, i.e., (Cr, Fe) 23 C 6 type of carbides within fully pearlitic matrix with minor amounts of retained γ -Fe were detected within the dominant matrix, i.e., pearlitic matrix in as-annealed condition. Detected magnitude and distributions of RSs on heat-treated sample resulted in higher tensile stresses in the surface and compressive in the interior as compared to sample in as-cast condition. Thus, this study was successfully in measuring RSs in as-cast and upon machining of hypoeutectic irons of HCWCI alloys using HDM.