针对全球范围减少能源消耗、降低碳排放的可持续发展需求，汽车行业急需探索和采纳更高效、更环保的燃料解决方案。甲醇（CH₃OH）因其丰富的来源、较低的生产成本以及良好的环保性能，是汽车领域替代传统燃料的主要可再生能源，但目前甲醇燃烧产物对发动机气缸内壁的腐蚀问题制约了甲醇发动机的发展。利用激光熔覆技术可以在发动机气缸或气缸套内壁表面制造耐磨耐蚀涂层，可有效解决燃料及其产物对发动机的腐蚀问题，提升发动机的使役寿命。但由于发动机气缸外形的不规则性，气缸内壁无法通过传统的内孔激光熔覆技术进行熔覆层的制备，限制了激光熔覆技术对发动机缸体基材表面处理的应用。基于此，本课题研究了适合甲醇发动机气缸工作环境的激光熔覆层的粉末体系，设计制造了一种适用于非回转体内壁的旋转激光熔覆装置，进而研究了气缸套内壁激光熔覆层的微观组织及性能。本课题主要研究内容及结论如下：

（1）研究了四种不同粉末体系所制备的熔覆层的宏观形貌、微观组织、硬度以及耐磨耐蚀性能，从而获得适合甲醇发动机气缸内壁的激光熔覆层的粉末体系。研究表明：四种熔覆层均成型良好且无宏观缺陷；CH-1熔覆层具有最高的硬度；随着润滑油中甲酸含量的增加，四种熔覆层的摩擦性能呈现出一定程度的下降，其中CH-1具有优异的摩擦磨损性能；CH-1、CH-2和CH-4熔覆层的电化学性能接近，其中CH-3熔覆层耐蚀性能较好。

（2）设计并加工制造了一种应用于发动机气缸内壁的可旋转高速激光熔覆设备，包括激光器、传动装置、旋转密封系统、激光熔覆头和固定装置。激光器光纤和中空传动系统相连，其下端连接旋转密封装置，实现了金属粉末、冷却水以及气体在熔覆过程中的旋转供给。本套设备解决了传统激光熔覆设备不能熔覆外形不规则的内孔，提高了激光熔覆设备的适用性，为甲醇发动机的改进提供了新的思路。通过对气缸内壁进行现场激光熔覆试验，表明该装置符合设计预期。

（3）选用前期研发的最优甲醇发动机工况的CH-1粉末体系，采用所设计制造的旋转熔覆设备，对所选定的发动机气缸套内壁进行熔覆，进而研究了气缸套内壁激光熔覆层的微观组织及性能。结果表明，旋转熔覆后的激光熔覆层表面气孔有所减少，微观组织没有发生明显变化，硬度分布、摩擦磨损以及电化学性能与常规高速熔覆层较为接近。旋转熔覆工艺可以作为可靠的加工方式对发动机气缸内壁进行强化。

In response to the global demand for sustainable development to reduce energy consumption and carbon emissions, the automotive industry urgently needs to explore and adopt more efficient and environmentally friendly fuel solutions. Methanol (CH₃OH) is a major renewable energy alternative to conventional fuels in the automotive sector due to its abundant sources, low production costs, and good environmental performance, but the development of methanol engines is currently constrained by the corrosion problem of methanol combustion products on engine cylinder walls. The use of laser cladding technology can be used to manufacture wear-resistant and corrosion-resistant coatings on the inner wall surfaces of engine cylinders or cylinder liners, which can effectively solve the problem of corrosion of fuels and their products on the engine and enhance the service life of the engine. However, due to the irregularity of the engine cylinder shape, the inner wall of the cylinder cannot be prepared by the traditional bore laser cladding technology for cladding layer, which limits the application of laser cladding technology to the surface treatment of the engine block substrate. Based on this, this study investigated the powder system of laser cladding layer suitable for the working environment of methanol engine cylinder, designed and manufactured a rotary laser cladding device for non-rotary inner wall, and then investigated the microstructure and properties of the laser cladding layer on the inner wall of the cylinder liner. The main research contents and conclusions of this project are as follows:

(1) The macroscopic morphology, microstructure, hardness and abrasion and corrosion resistance of the cladding layers prepared by four different powder systems were investigated, to select the most suitable powder system for the laser cladding of the cylinder walls of methanol engines. The studies indicated that: all four claddings were well formed and free of macroscopic defects; the CH-1 cladding had the highest hardness; the friction performance of the four claddings showed a certain degree of decrease with the increase of formic acid content in the lubricant, among which CH-1 had excellent friction and wear performance; the electrochemical properties of the CH-1, CH-2 and CH-4 claddings were close to each other, among which the corrosion resistance of the CH-3 cladding was better.

(2) Designed and manufactured a rotatable high-speed laser cladding equipment for engine cylinder walls, including laser, transmission device, rotary sealing system, laser cladding head and fixing device. The laser fiber is connected to the hollow transmission system, and the lower end is connected to the rotary sealing device, which realizes the rotary supply of the metal powder, cooling water and gas in the process of cladding. This equipment solves the problem that traditional laser cladding equipment could not melt the irregular shape of the bore, improves the applicability of laser cladding equipment, and provides a new idea for the improvement of the methanol engine. The on-site laser cladding experiment on the cylinder liner bore shows that the device meets the design expectation.

(3) The CH-1 powder system, which was developed for optimal methanol engine conditions, was used to coat the inner wall of the cylinder liner of the selected engine using the rotary cladding equipment designed and manufactured by the company, and the microstructure and properties of the laser cladding layer on the inner wall of the cylinder liner were investigated. The results showed that the surface porosity of the laser cladding layer after rotary cladding was reduced, the microstructure did not change significantly, and the hardness distribution, friction and wear, and electrochemical properties of the cladding layer were close to those of the conventional high-speed cladding layer.