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本文简要介绍和讨论了气阀的工作环境,可能的失效模式,气阀结构,气阀材料和用于评估气阀能力的各种台架试验。内燃机中的排气阀由于受腐蚀和热机械应力的影响,可能导致阀顶和阀盘与阀杆连接处材料的过度损失。在极端的条件下,会产生腐蚀疲劳失效。失效,或者是功能降低,都可能随着出现由于磨损、喷蚀或是阀面烧伤引起的密封下降。气阀的低温区,机械应力会导致定位沟槽和气阀杆尾端产生疲劳或磨损而失效。 气阀结构可由单一气阀合金或者是根据发动机对气阀性能的要求由几种材料组成。最常见的结构方案是加一个镶片,对焊阀杆、锥面堆焊硬质合金和杆部增加镀层。材料中有一大系列可满足其性能要求。它们可归类为排气阀材料,进气阀材料,锥面堆焊材料,杆部材料和镶片材料。排气阀材料为耐热沉淀硬化不锈钢(PHSS)或者是能在(1500°F)816℃温度范围工作的镍基超耐热合金。进气阀材料为普通低合金钢,或者是可在538℃以下工作的合金钢。过去常用的钴基硬质堆焊合金将要被新发展起来的耐磨、耐冲刷和耐腐蚀性良好的铁基合金所代替。 要选择合适的材料,比较流行的作法是在实验室进行一系列的力学性能试验和台架腐蚀试验来评估材料的功能。力学性能试验有:抗张,应力破断,蠕变,疲劳(光滑试样或缺口试样),磨损,硬度和冲
This article briefly introduces and discusses the working environment of the gas valve, the possible failure modes, the valve structure, the valve material, and various bench tests used to evaluate the valve’s ability. Exhaust valves in internal combustion engines can suffer from excessive corrosion due to corrosion and thermo-mechanical stresses that can cause excessive material loss at the valve plug and stem connections. In extreme conditions, will produce corrosion fatigue failure. Failure, or reduced functionality, may decrease with the seal due to wear, erosion or surface burn. Low temperature valve area, mechanical stress will lead to positioning groove and valve stem fatigue or wear and failure. The valve structure can consist of a single valve alloy or several materials depending on engine performance requirements for the valve. The most common construction solution is to add an insert, butt-weld stem, tapered surfacing cemented carbide and stem plating. There is a large series of materials to meet their performance requirements. They can be categorized as exhaust valve material, intake valve material, cone surfacing material, stem material and insert material. Exhaust valve material is heat-resistant, precipitation-hardened stainless steel (PHSS) or a nickel-based superalloy capable of operating at (1500 ° F) 816 ° C. Intake valve material is ordinary low alloy steel, or can work below 538 ℃ alloy steel. Cobalt-based hardfacing alloys, commonly used in the past, are to be replaced by the newly developed wear-resistant, erosion-resistant and corrosion-resistant iron-based alloys. To choose the right material, it is more common practice to perform a series of mechanical and bench corrosion tests in the laboratory to evaluate the function of the material. Mechanical properties tests are: tensile, stress rupture, creep, fatigue (smooth or notched specimen), wear, hardness and punch