| WANG Lin,CAO Xiuquan,HE Jiarong,HU Guangzhong,LI Chao.Surface Strengthening Mechanism of Q235 Based on Laminar Plasma Jet[J],54(9):112-120 |
| Surface Strengthening Mechanism of Q235 Based on Laminar Plasma Jet |
| Received:July 21, 2024 Revised:December 11, 2024 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2025.09.009 |
| KeyWord:Q235 steel laminar plasma jet surface hardening microstructure distribution wear resistance wear mechanism |
| Author | Institution |
| WANG Lin |
School of Mechanical Engineering, Sichuan University of Science & Engineering, Sichuan Yibin , China |
| CAO Xiuquan |
School of Mechanical Engineering, Sichuan University of Science & Engineering, Sichuan Yibin , China |
| HE Jiarong |
School of Mechanical Engineering, Sichuan University of Science & Engineering, Sichuan Yibin , China |
| HU Guangzhong |
School of Mechanical Engineering, Sichuan University of Science & Engineering, Sichuan Yibin , China |
| LI Chao |
School of Mechanical Engineering, Chengdu University of Technology, Chengdu , China |
|
| Hits: |
| Download times: |
| Abstract: |
| Due to its comprehensive performance, easy processing, low cost, etc., Q235 steel has been widely used to manufacture various metal parts in the industrial fields. However, parts made of Q235 steel always fail due to part wear and tear, which limit the service life of these parts. For prolonging the service life of the parts made of Q235 steel, various surface hardening methods have been used to improve their surface qualities. As a novel surface hardening method, a home-made laminar plasma surface hardening method was used to harden the surface of Q235 steel for improving its wear resistance and hardness. Firstly, based on the home-made laminar plasma surface hardening system, the influences of the arc currents (90- 120 A) and the quenching distances (40-70 mm) on the surface wear resistance and hardness of Q235 steel were investigated by single factor control variable method. Then, the microstructure, hardness and wear resistance of Q235 steel before and after hardening were characterized and analyzed by metallographic microscope, scanning electron microscope (SEM), Vickers hardness tester, ultra depth of field, ultra-depth-of-field microscopic 3D workstation and white light interferometer to reveal the surface hardening mechanism of Q235 steel. The following experimental results were shown. The cross section of the hardened sample could be divided into three parts:hardened zone, heat affected zone and substrate, in which the hardened layer shaped as a "crescent"; the hardened zone was composed of dense lath martensite structure, while the heat affected zone was composed of residual austenite, martensite, ferrite and cementite. When the quenching distance and other parameters were constant, the depth, width, hardness and wear resistance of the hardened zone increased with the increase of the arc current. When the arc current and other parameters were constant, the depth, width, hardness and wear resistance of the hardened zone decreased with the quenching distance. In addition, when the arc current and quenching distance exceeded a certain value (I≥120 A or d≤50 mm), the surface of the substrate would be micro-fused, which would affect the topography and quality of the hardened zone. Besides, the corresponding hardness near the microfusion zone was lower than the hardened zone. More importantly, when the quenching distance was too large (d≥70 mm), the hardness and wear resistance of the hardening zone were sharply reduced:the maximum hardness of the hardened zone decreased from 265HV0.2 to about 232HV0.2 and the wear rate of the hardened zone increased from 1.62×10‒5 mm3/(N.m) to 3.46×10‒5 mm3/(N.m). Thus, the hardening quality of the substrate could be influenced by the quenching distance obviously. Overall, the maximum hardening depth of Q235 was 1.58 mm. The surface hardness increased by about 63%, and the friction coefficient and the wear rate reduced by about 0.108-0.234 and at least 39% respectively. Under dry friction conditions, the wear mechanism of the substrate was mainly abrasive wear, while the wear mechanism of the hardened zone was mainly abrasive wear and adhesive wear. Besides, the wear resistance and hardness of the pats were positively correlated with the working current, and negatively correlated with the quenching distance. Therefore, laminar plasma can be used as a new heat source to strengthen Q235 workpieces to improve surface wear resistance and hardness for prolonging their service life. |
| Close |
|
|
|