Analysis On Microstructure And Wear Resistance Of Iron-Based Coatings Deposited By Thermal Spraying For Cylinder Blocks

In this paper, to improve the wear resistance of aluminum alloy engine block, three solutions are briefly contrasted. To improve the wear resistance of aluminum alloy, the majority of the aluminum alloy engine blocks are equipped with cast iron cylinder liner with the thickness between 1.5mm to 3mm. However, this method has the following disadvantages: the liner itself increase increases the weight of about 1.5kg, and taking into account the needs of cylinder machining and assembly, engine block also need to increase the overall size. Second, the need to rely on cast iron cylinder liner manufacturing process, taking into account the casting performance, its composition can not be flexible changed, it is difficult to provide the best combination of friction pair with piston. The efficiency of the engine will be significantly affected by these problems. While using thermal spray technology to prepare the engine block can overcome these shortcomings.In this article, the preparations of thermal spray cylinder coating technology were summarized, as well as the principles, characteristics and application of arc spraying technology and the effect of spray parameters on coating performance.Five iron-based materials, 08Mn2Si, 08A, 4Cr13, 65Mn, 08CrMoVA, were prepared by arc spraying. The microstructures of these iron-based coatings were analyzed by optical microscope and scanning electron microscope. The results showed that: these coatings showed a flat layered structure, the majority of oxides and porosity lied in the flat particles'border, only a little distributed inside the particles. The porosity proportions of the coatings were measured by metallographic analysis system. The results were as follows: 6.17%, 4.48%, 3.32%, 5.56%, 6.59%. FeO oxide was detected in all the coating specimens, by X-ray diffraction analyzer. The micro-hardness of these coatings was 231.2HV, 213.8HV, 287.9HV, 328.9HV, 226.6HV respectively. The friction coefficient and wear resistance of these coatings were determined on the MMW-1 vertical omnipotence friction wear testing machine, under lubrication and dry friction conditions. Provide a reference for the preparation of thermal spray cylinder coating material selection. The wear test results revealed that, in all of the wear tests, the coating wear were mainly abrasive wear. Under fluid lubrication conditions, coefficient of friction and wear resistance of the 4Cr13 coating were the best and better than the gray cast iron. Under boundary lubrication conditions, FeO oxides and pore reduced the coefficient of friction. Friction coefficient and wear resistance of the 08A and 4Cr13 coatings were better than the gray cast iron. Tests under dry wear conditions showed that the minimum friction coefficient of the gray cast iron, but the weight loss maximum; friction coefficient of 08Mn2Si coating is slightly higher than that of gray cast iron, but the weight loss minimum. The harder, the better wear resistance of the coatings, but worse of the counterpart at this point.