Guangzhi He

Under extreme conditions in fields including aerospace exploration, deep earth excavation, and ocean engineering, mechanical components are subjected to severe environmental challenges, such as high temperature, heavy load, fatigue fracture and corrosion, which significantly limit their service life and operational reliability. Surface engineering has emerged as a critical strategy to address these problems by modifying surface characteristics while preserving basic properties of raw materials. Among various surface modification techniques, laser-based surface modification stands out due to its precise processing, high throughput, and outstanding surface performance. However, laser-based surface modification of metallic materials for industrial applications remains limited owing to inadequate systematic understanding regarding the fabrication mechanisms. Accordingly, a comprehensive and holistic review is essential to elucidate the effect of laser-based surface modification on process optimization, system development, microstructure evolution, and performance enhancement. This review systematically expounds two fundamental strategies in laser surface modification-based material modification (exemplified by laser cladding) and structural modification (exemplified by laser shock peening) in terms of mechanism, process, performance and application. In addition, the mechanism and potential of the synergistic integration of LC (laser cladding) and LSP (laser shock peening) are emphatically discussed. Finally, perspectives regarding process optimizations, material developments, and system improvements for laser surface engineering are presented. By establishing a clear “mechanism–process–performance–application” narrative, this review aims to provide both a scientific reference and a practical guideline for the severe demands of extreme operating conditions.

Metallic micro/nano structures with special physicochemical properties have undergone rapid development owing to their broad applications in micromachines and microdevices. Ultrafast laser processing is generally accepted as an effective technology for functional structures manufacture, however, the controllable fabrication of specific metallic micro/nano structures remains a challenge. Here, this work proposes a novel strategy of laser induced transient solid‐liquid transition to fabricate unique structures. Through modulating the transient state of metal from solid to liquid phase using the initial pulse excitation, the subsequent ultrafast pulse‐induced recoil pressure can suppress the plasma emission and removal of liquid phase metals, resulting in the controllable fabrication of coffee‐ring structures. The solid‐liquid transition dynamics, which related with the transient reflectivity and plasma intensity, are revealed by established two temperature model coupled with molecular dynamics model. The coffee‐ring structure exhibits tunable structure color owing to various optical response, which can be used for color printing with large scale and high resolution. This work provides a promising strategy for fabricating functional micro/nano structures, which can greatly broaden the potential applications.

Laser shock peening is conducted to enhance the mechanical properties of metals. Efficient optical absorption of metal surface is desirable to increase the laser shock peening depth. In this work, a method is proposed to regulate the absorption behavior by surface colorizing to increase the affected depth and magnitude of nanosecond laser shock peening (NLSP). Colorized samples are fabricated with high absorption of 400–1500 nm, which is 89% higher than that of un‐colorized samples. This regulated optical response is attributed to the multi‐reflection/absorption behavior within nano‐to‐micro‐scale structures. Nano‐to‐micro‐scale structure‐based approaches offer controllable concurrent tailoring of a higher residual stress depth and greater magnitude. Black samples exhibit higher affected depth (64.71%) and magnitude (17.87%) values for the compressive residual stress than un‐colorized samples with unit peak power density after NLSP. Experimental results show that coarse grains are refined on surfaces, and the depths of grain refinement and dislocation propagation increase for colorized samples, which exhibit a regulated surface optical behavior. Therefore, this study presents a promising approach that the regulation of surface optical absorption of metals can be incorporated into the improvement of laser shock peening depth.

Objectives We updated the experience on percutaneous microwave ablation for renal cell carcinoma with five-center data and long-term follow-up. Methods This retrospective study reviewed the T1N0M0 renal cell carcinoma patients who underwent microwave ablation between April 2006 and December 2019. Clinicopathological and procedural data were collected. Technical effectiveness and complications were assessed, and the Kaplan-Meier method was used for cancer-specific survival, disease-free survival, overall survival, and local neoplastic process analyses. Results A total of 323 consecutive patients (mean age, 62.9 years ± 14.0) with 371 biopsy-proved tumors (mean diameter, 2.9 cm ± 1.2) were enrolled, and 42.6% of the tumors were located adjacent to collecting system/bowel and technical effectiveness was achieved in 360 (97.0%) tumors. For 275 cT1a patients, during median follow-up time of 66.0 months (IQR, 58.4–73.6), 10-year local neoplastic processes, cancer-specific survival, disease-free survival, and overall survival rates were 1.9%, 87.4%, 71.8, and 67.5%, respectively. For 48 cT1b patients, during the median follow-up time of 30.4 months (IQR, 17.7–44.8), 5-year local tumor progression, cancer-specific survival, disease-free survival, and overall survival rates were 11.3%, 91.4%, 69.1, and 89.2%, respectively. Major complications showed no differences between cT1a (3.5%) and cT1b (6.9%) patients (p = 0.28). A clinical risk stratification system was developed based on multivariable model to predict DFS and CSS with c-indexes of 0.78 (95% CI: 0.71–0.85) and 0.77 (95% CI: 0.65–0.90), respectively. Conclusions With matured follow-up at five institutions, ultrasound-guided percutaneous microwave ablation is a reliable treatment option for cT1a renal cell carcinoma even in dangerous location and appears to be promising for cT1b tumors. Key Points • To our knowledge, this is the first multicenter cohort of long-term oncologic outcomes with percutaneous MWA of cT1 RCC. • The predicting model we developed is accurate to predict the long-term DFS and CSS, which can help to provide a better MWA prognostication over routinely available clinical information. • The available evidence shows that microwave ablation of clinical stage T1 RCC is safe and reliable with promising long-term oncologic outcomes, especially for cT1a RCC with excellent 10-year results.