There has been considerable interest in low energy (30–120 keV) electron beam surface treatment for both hardening and corrosion protection of steels and other alloys.[1] Techniques involve either melting the surface or raising the temperature to near melt and relying on self-quenching to rapidly cool the material below the critical transition temperature. With iron, for example, both carbon and carbides are dissolved in both the austenite (above 910 °C) and liquid phases. The rapid cooling to below 710 °C prevents growth of large ferric carbide (Fe3C) or cementite crystals and thus produces a much harder surface. At sufficiently high cooling rates martensite or even amorphous compositions can be produced.[2] With previously used low-energy electron beams, only the top 10 to 100 μm of the material is directly heated by the electrons, although the heat affected zone may extend much further into the material. Recent accelerators have been developed in the high-current beam propagation program which have both high current density (>10 kA/cm2), higher energy (up to 50 MeV), and high average beam power (150 kW). The advantage of using a high-energy machine is that the electron range is much greater. This leads to modifying bulk properties of the material and not just changing surface properties. For example, the range of 10 MeV electrons is nearly 1 cm in iron. The question that remains is whether it is possible to self-quench sufficiently fast when the material is heated to greater depths. We propose theory and experiments to study these effects. Theory will involve use of available PIC codes, such as ISIS, for electron deposition, and a radiation transport code, such as CYLTRAN, for radiation transport and deposition. These will provide input to thermal transport codes for determination of heat flow rates. Experiments will consist of irradiating samples with high power, high-energy bea- s and measuring the resulting materials changes.
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机译：低能（30–120 keV）电子束表面处理对钢和其他合金的硬化和腐蚀保护引起了极大的兴趣。 [1] 技术涉及熔化表面或提高温度。几乎融化并依靠自淬火将材料快速冷却到临界转变温度以下。例如，对于铁，碳和碳化物都溶解在奥氏体（高于910°C）和液相中。快速冷却至710°C以下可防止大型碳化铁（Fe3C）或渗碳体晶体的生长，从而产生硬得多的表面。在足够高的冷却速率下，可以产生马氏体甚至非晶态成分。 [2] 使用先前使用的低能电子束，只有顶部10至100μm的材料被电子直接加热，尽管热影响区可能会进一步延伸到材料中。在大电流束传播程序中已经开发了最新的加速器，这些加速器既具有高电流密度（> 10 kA / cm 2 ），又具有较高的能量（高达50 MeV）和较高的平均束功率（ 150千瓦）。使用高能机器的优点是电子范围更大。这导致修改材料的整体性质，而不仅仅是改变表面性质。例如，铁中10 MeV电子的范围接近1 cm。仍然存在的问题是，当将材料加热到更大的深度时，是否有可能足够快地进行自我淬火。我们提出理论和实验来研究这些影响。理论将涉及使用可用的PIC代码（例如ISIS）进行电子沉积，以及使用辐射传输代码（例如CYLTRAN）进行辐射传输和沉积。这些将为热传输代码提供输入，以确定热流率。实验将包括用高功率，高能量的光束照射样品，并测量由此产生的材料变化。
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