Study On Wear Resistance And Impact Fatigue Performance Of M42 High-speed Steel

M42 is a high-performance high-speed steel with high hardness,high wear resistance,and good impact fatigue resistance,which is widely used in cutting tools and punch materials.The common failure modes of M42 high-speed steel are wear and fatigue fracture damage fracture.However,there is a lack of detailed reports on the relationship between the service performance of M42 high-speed steel and microstructure and residual stress.This paper focuses on the research of residual stress and microstructure evolution on the wear and impact fatigue performance of M42 high-speed steel and reveals the performance damage and tissue damage mechanisms.A comparative analysis was conducted on the microstructure and wear performance of China’s HEYE(HYM42)and Japan’s NACHI Steel(NM42)M42 high-speed steel.The study found that the tempered microstructure of HYM42 and NM42 consisted of tempered martensite matrix and a large amount of carbides distributed in the matrix.The wear resistance of NM42 high-speed steel is better than that of HYM42 high-speed steel.The wear mechanism of both HYM42 and NM42 steel includes adhesive wear,abrasive wear and slight oxidation wear.Although the wear surface roughness of both steels is comparable,the wear deformation scratch distribution of NM42 steel is more uniform.Moreover,observation of the longitudinal section morphology shows that the plastic deformation layer of HYM42 steel is deeper.Lower hardness and less carbide content is why HYM42 steel has poorer friction and wear performance than NM42 steel.The wear mechanism diagram of M42 high-speed steel was established using the orthogonal experimental method,and the wear damage mechanism of M42 high-speed steel was analyzed based on the surface morphology of the wear.According to the difference in wear rate,the wear diagram was divided into three areas:slight wear,moderate wear,and severe wear.With the increase of contact stress and sliding speed,the damage mechanism of high-speed steel underwent three stages of evolution:ploughing+micro-pores caused by the peeling of a small amount of carbides→slight delamination+micro-pores caused by the fracture and peeling of more carbides→more severe delamination+micro-pores caused by the fracture and peeling of a large amount of carbides.The fracture and peeling of carbides are the dominant factors in the wear and damage of M42 high-speed steel.A comprehensive evaluation of wear resistance w’was established using three-dimensional morphology feature parameters(R_a,R_q),carbide cracking or peeling area ratio(Acarbide),and the grey correlation degree method and entropy method were used to determine the service evaluation system of wear resistance and wear damage:w’=0.4565R_a+0.4317R_q+0.1118Acarbide.It was found that when it is greater than 0.9222,the wear damage is more severe.The impact fatigue performance of HYM42 and NM42 high-speed steel was studied using an impact fatigue testing machine.The results indicate that the relationship between fatigue life and impact energy of HYM42 and NM42 high-speed steel can be quantitatively characterized as lg E_i=3.84-0.69 lg N_f and lg E_i=3.37-0.64 lg N_f,respectively.As the impact energy increases,the impact fatigue life decreases,and for the same impact energy,the fatigue life of HYM42 high-speed steel is better than that of NM42.Observation of crack morphology shows that fatigue cracks mainly originate at interfaces between the specimen surface or large-sized carbides(≥10μm)and the matrix,and they can also propagate along interfaces between the plastic flow layer and the matrix or the original austenite grain boundary.Additionally,small-sized carbides(1-3μm)can hinder crack propagation or alter the direction of crack propagation,which can effectively slow down the crack propagation rate and be advantageous to fatigue performance.The residual stress distribution law of M42 high-speed steel actual punch before and after heat treatment was studied using the Japanese rheological Automate-ⅡX-ray diffractometer.The results showed that under the extrusion state,the transverse residual stress at the tip of the M42 high-speed steel actual punch was tensile stress,and the transverse residual stress at the bottom of the punch was compressive stress,which could reach up to-600MPa.After heat treatment,the axial residual stress of the punch was mostly compressive stress,and the transverse residual stress at the root of the punch changed from compressive stress to tensile stress.The residual tensile stress at the root was the main cause of the fracture during the use of the punch.