Special Issue: Advancement in Heat Treatment and Surface Modification for Metals

Heat treatment is a pivotal process that gives metal materials their desired structure and plays an irreplaceable role in comprehensively enhancing individual components’ performance. It goes beyond mere heating and cooling, representing a sophisticated technique that actively regulates the microstructure of metals through the precise control of the temperature, time, and cooling method. In nearly all core metal components, to achieve exceptional performance in terms of equipment efficiency, safety, and longevity, heat treatment technology is crucial [1,2,3,4]. Since the failure of large components usually originates at the surface or sub-surface, surface modification is a key core technology in achieving optimal service performance and thus meeting the advanced requirements for large components posed by harsh service environments [5,6,7,8,9].

This Special Issue offers researchers and practitioners up-to-date information on recent advances in heat treatment and surface modification for metals. The contributions include original research papers and reviews in related fields. Our contributions comprise a range of advanced perspectives, enhancing our collective understanding of advances in heat treatment and surface modification for metals. Significant progress in metals is being achieved not only through novel composition design but also through performance enhancements enabled by heat treatment and surface modification.

Fourteen papers are included in this Special Issue, and, to highlight the high quality of the efforts and progress made by these outstanding authors, their contributions are briefly summarized below.

Liang et al. [10] investigated performance enhancement in copper-bearing ultra-low-carbon, high-strength steels by tempering them at different temperatures; their findings indicated that the strength of this type of steel can be significantly enhanced through tempering at appropriate temperatures, and the main strengthening mechanism is precipitation strengthening by nanoscale copper CRPs and CN atomic clusters. Wang et al. [11] developed a self-designed measuring device to capture the thermovoltage curves of 45 carbon steel during continuous cooling and achieved the in situ characterization of bulk transformations during the heat treatment process. Chu et al. [12] studied the embrittlement of steel grain boundaries caused by the penetration and diffusion of liquid copper; their research findings are consistent with the argument that the corresponding material states of premelted GBs are different from those of solid-state GBs, thus providing experimental evidence for the diffusion equation solutions and enabling a better understanding of how to prevent liquid metal embrittlement. Huang et al. [13] investigated the effects of annealing time on the structural characteristics and magnetic properties of FeSiBPCCuNb amorphous ribbons and found that the ribbons had good soft magnetic properties and the saturation magnetic induction reached a peak value after annealing at 550 °C for 20 min. Wang et al. [14] reported the effects of Gd/Nd ratio and aging treatment on the wear behavior of Mg-Nd-Gd-Sr-Zn-Zr alloys; their results indicated that the T5 alloy with a Gd/Nd ratio of 1/3 has the best wear resistance, and the wear mechanisms mainly include abrasive wear, oxidation wear, and delamination wear. Wang et al. [15] reported that the constituents of recrystallized and deformed structures were strongly affected by cold rolling reduction rates and recrystallization temperatures. Meng et al. [16] studied the corrosion performance of an Epoxy/Sulfur–Selenium coating on Q235 steel; the results indicated that the E/S-Se coating exhibited much better corrosion resistance than the Q235 steel substrate. He et al. [17] reported that both the nitriding efficiency and wear resistance can be greatly enhanced via Al modification during plasma nitriding. Zeng et al. [18] investigated the effect of thermal oxidation (TO) on ultra-low wear behaviors in the Ti6Al4V alloy at high temperatures. Ni et al. [19] analyzed a novel effect of post-oxidation on the comprehensive performance of the plasma nitriding layer; their results demonstrated that post-oxidation could simultaneously improve the toughness, hardness, and wear resistance of the nitrided samples. Zhang et al. [20] investigated the friction behavior of MoS2/PTFE-coated cemented carbide fabricated with a spray technique in dry friction conditions and found that MoS2/PTFE coatings represent a promising approach to enhancing the friction performance of traditional cemented carbide. Liu et al. [21] investigated the effect of warm shot peening on microstructure evolution and residual stress in gradient-nanostructured Mg-8Gd-3Y-0.4Zr alloys. Dai et al. [22] reviewed current research and development trends in wire arc additive manufacturing (WSSM) technology for aluminum alloys and proposed future research directions based on the application status of the WAAM aluminum alloy. Zhou et al. [23] summarized the effects of five commonly used types of accelerating method (including process parameter optimization, surface mechanical nano-crystallization, surface-active catalysis, surface pre-oxidation, and surface laser treatment) on results in gas nitriding, compared their advantages and disadvantages, and then proposed a multi-technology collaborative processing acceleration method.

In conclusion, this Special Issue is a comprehensive resource that will foster innovation and dialog among researchers, engineers, and industry experts in relevant fields.