设备, 组件, and machinery failures can lead to significant costs, including business interruption and equipment replacement. Was the manufacturing faulty? Has it been operated correctly? Has the maintenance been insufficient? Could the failure have been predicted or avoided? 这些问题的答案对设备供应商来说意义重大, owners/operators and insurance companies.
腐蚀和磨损引起的表面退化是设备故障最常见的原因之一. 虽然两者都可以很容易地从机器部件的外观来识别, 法医工程师面临的挑战是确定这些故障发生的方式和原因.
Determining Mechanisms of Corrosion
当易感合金暴露在适当的环境条件下, chemical degradation can occur causing metal corrosion. 例如, mild steel is a common engineering material, but it will corrode when exposed to water and oxygen. 钢材腐蚀引起的过早失效往往是由于防腐蚀措施失效造成的.
Although general corrosion can occur slowly, 一些腐蚀机制会产生局部侵蚀条件，加速穿壁腐蚀, causing leaks and holes in a matter of weeks or months. 从失效部件上切割出的通壁金相切片可以帮助可视化腐蚀机制(例如:腐蚀机理).g., cracking or pitting).
合金的化学分析也可以帮助确定其易受腐蚀的机制. 冶金调查将把化学分析的结果与维修记录和水分析的信息结合起来. Evidence from where the corrosion occurs (e.g., 在接头或焊缝附近或污泥积聚的地方)以及它在整个系统中的广泛程度可以帮助确认机制和可能的原因.
Investigating Wear
Wear is the other common surface degradation failure mode. 它有时与腐蚀一起出现，并受到金属性能和环境条件的影响. 磨损是一个问题，因为磨损的部件失去厚度，薄的区域可能爆裂. 此外，运动部件可能会因摩擦加热而松动、振动或卡住. Although moving parts are protected from wear by appropriate lubrication, 磨损碎屑会积聚在润滑油中，并在油再循环时加剧问题.
法医材料工程师可以尝试将在底油中发现的污泥和固体颗粒与仍然嵌入磨损表面的磨损颗粒相匹配. 使用扫描电子显微镜进行高倍检查可以帮助确定颗粒大小和形状，并确定碎片的组成. 调查的路线将取决于磨损是否由硬污染物颗粒引起, loose corrosion oxides or contact fretting debris from the surface.
Preventing Corrosion and Wear Failures
磨损和腐蚀可以在很长一段时间内低水平发生，而不会导致设备故障. 但随着它们的发展，腐蚀产物和磨损碎片可能会在机械的其他地方产生问题. If these issues can be detected and acted upon at an early stage, it’s possible to prevent a major and sudden failure. Pre-emptive maintenance, routine water and oil sampling, and condition monitoring are key to preventing breakdown.
防止腐蚀的最好方法之一是在钢铁设备的设计和运行的早期实施预防措施. 腐蚀防护通常包括使用水化学处理和屏障涂层，以防止暴露在腐蚀性环境条件下. 保护措施可能包括在储水罐中加入化学抑制剂, 锅炉, 管道工程, or plumbing as well as coating surfaces with paint, 塑料, 或混凝土.
When an equipment failure occurs, 表面上的故事并不是法医工程师需要讲述的全部故事. 仔细观察表面损伤和外观通常可以为建立调查提供关键证据.