Sliding Wear Behavior of Low-Alloy High-Strength Marteniste Wear-Resistant Steel by On-Line Quenching

Compared with the off-line quenching processing route, the reheating process for austenitizing can be saved during the on-line quenching process, which shows the advantages of short production cycle, less emission and low cost. The on-line quenching technology has great development potential in the production of low-alloy wear-resistant steel, but there are few researches on the preparation of high-strength wear-resistant steel by the on-line quenching treatment. The microstructure and properties of two high-strength martensitic wear-resistant steels prepared by on-line quenching were studied by optical microscope, scanning electron microscope, tensile test, impact test and sliding wear test. The results showed that the yield strength and tensile strength of two steels were above 1 450 and 1 850 MPa, respectively. Simultaneously, the impact toughness of sample with thickness of 7.5 mm was more than 30 J, indicating that the prepared two martensite steels possessed ultrahigh strength and good toughness. The high strength was attributed to the addition of more Ti content in 1# steel and more Nb content in 2# steel, which presented the precipitation strengthening and refinement strengthening, respectively. Meanwhile, the additions of Ni and Cr were conductive to the low temperature impact toughness. Additionally, with the load increased from 10 N to 50 N, the mass loss increased obviously, while the mass loss of steel at 90 N was less than that at 50 N. During the reciprocating wear test, the wear resistances of two steels were similar at lower loads of 10 N and 50 N, but difference of wear resistance appeared at higher load of 90 N. When the hardness increased by about 7%, the wear degree was reduced by 13.6% at 90 N. Moreover, the depth of the hardening layer increased monotonously with the increase of load, and the severe plastic deformation layer was only observed at loads of 50 N and 90 N of 1# steel with lower hardness. Furthermore, with the decrease of load, the wear mechanism changed from the original combination of oxidizing wear and adhesive wear to abrasive wear and adhesive wear. With regard to the friction coefficient, it varied within 0.66~0.80 under different loads of the two types of steels, and it also increased firstly and then decreased with the increase of load. More importantly, the average influence factor caused by the load change was 1.294, which was much higher than that caused by the hardness change. Therefore, compared with the hardness, the friction coefficient was obviously more sensitive to the load, and the sensitivity degree increased with the increase of the load. Finally, on the one hand, high load reduced the friction coefficient, leading to the decrease of the absolute stress of. On the other hand, high load increased the contact center pressure, resulting in the increase of the absolute stress value of . Thus, the influences of applied load and friction coefficient on the contact stress were competitive, and the competitive relationship between these two aspects determined the ultimate stress state of the system. In this paper, the applied load played a major role in determining the contact stress. The phenomenon that the loss of wear decreased with the increase of load under high load might be related to this process.