The appearance of machining burr as a cracking failure on twistlock pin

Abstract The failure analysis of the twist lock pin made of alloy steel is presented. The pin was visually observed to have a cracking character at curvature area after 45,000 cycles. Some non-destructive inspections were previously done. However it failed to detect any crack defect. The twist lock pin sample was further macro and microscopic analysis. The analysis found that the surface discontinuities that were previously presumed as a cracking morphology was actually a machining burr and improper machining marks. There were some micro- and nano-sized pinholes dispersed over the metal matrix of the twistlock pin sample. The microstructure of the twistlock pin was tempered martensite structure.