Effects of in situ NbC on the microstructure and high-temperature friction wear properties of 4Cr5MoSiV1 steel

Abstract

High-temperature wear is a common wear loss in medium heat-resistant hot-work die steels. In this study, NbC-reinforced 4Cr5MoSiV1 composites were prepared by using an in situ method to increase their high-temperature wear resistance. SEM, EBSD, and TEM were used to analyze the morphology, distribution, and microstructure of NbC in composites with different NbC volume fractions. The NbC gradually became “allotriomorphic” and was more uniformly distributed in the composites as the volume fraction increased from 1 vol%, 3 vol% to 5 vol%. High temperature friction wear tests showed that the wear rate of composites with NbC was lower than NbC-free ones. The wear rate of the composites with 5 vol% NbC increased from 2.51 × 10−8 mm3 N−1 ± 0.12 m-1 to 7.07 × 10−8 ±0.35 mm3 N−1m−1. While that of the NbC-free ones increased from 5.05 × 10−8 ± 0.25 mm3 N−1m−1 to 1.727 × 10−7 ± 0.86 mm3 N−1m−1 when the temperature was increased from 200 °C to 400 °C. The wear rate of the NbC-free samples was 1.727 × 10−7 ± 0.86 mm3 N−1m−1 at 400 °C, while that of samples with 5 vol% NbC was 7.07 × 10−8 ± 0.35 mm3 N−1m−1. Their wear mechanisms were oxidative wear, abrasive wear, and adhesive wear. This study provided ideas for work on the development of wear-resistant composites and promising applications in wear-resistant engineering products, such as shovel teeth and shield machine tool rings in mining and tunneling.