Tailoring microstructure and wear resistance of Cr–Mo alloy steel: The synergistic effects of squeeze casting and melt degassing treatment

The medium-carbon low-alloy Cr–Mo steel liners with ultra-larger size of 768 mm × 466 mm × 140 mm were produced by squeeze casting (SC) and the traditional sand gravity casting (GC) process, and the effect of degassing treatment before squeeze casting (SC-DT) on the mechanical properties and impact abrasion wear resistance were systemically investigated. The result shows that the original austenite grain size was refined by squeeze casting, and the degassing treatment before squeeze casting can further refine the grain size and decrease casting defects. The grain refinement induced by squeeze casting and degassing treatment could significantly enhance the mechanical properties of low-alloy Cr–Mo steel. Compared with the GC sample, the SC sample exhibited increases of 2.18 % in yield strength, 43.66 % in uniform elongation, 0.8 % in hardness, and 56 % in impact toughness. Compared with the SC sample, the SC-DT sample showed further increases of 4.85 % in yield strength, 48.28 % in uniform elongation, 3.14 % in hardness, and 187.1 % in impact toughness. However, the three-body impact abrasive wear performance of the SC-DT sample contradicted its excellent mechanical properties, exhibiting higher wear loss and wear rate than both the SC and GC samples. The sample produced by squeeze casting without degassing treatment observed the best three-body impact abrasive wear performance. The wear mechanism includes micro-ploughing, micro-cutting and surface fatigue. The excellent wear resistance of SC sample is contributed by the well-matched hardness and toughness.