Samoila Cornel, Ursutiu Doru, Schleer Walter-Harald, Jinga Vlad, Nascov Victor
Department of Materials Science, Transylvania University of Brasov, Brasov 500036, Romania.
Department of Electronics and Computer Science, Transylvania University of Brasov, Brasov 500036, Romania.
Materials (Basel). 2016 Oct 5;9(10):819. doi: 10.3390/ma9100819.
In manufacturing processes involving diffusion (of C, N, S, etc.), the evolution of the layer depth is of the utmost importance: the success of the entire process depends on this parameter. Currently, nitriding is typically either calibrated using a "post process" method or controlled via indirect measurements (H2, O2, H2O + CO2). In the absence of "in situ" monitoring, any variation in the process parameters (gas concentration, temperature, steel composition, distance between sensors and furnace chamber) can cause expensive process inefficiency or failure. Indirect measurements can prevent process failure, but uncertainties and complications may arise in the relationship between the measured parameters and the actual diffusion process. In this paper, a method based on noise and fluctuation measurements is proposed that offers direct control of the layer depth evolution because the parameters of interest are measured in direct contact with the nitrided steel (represented by the active electrode). The paper addresses two related sets of experiments. The first set of experiments consisted of laboratory tests on nitrided samples using Barkhausen noise and yieded a linear relationship between the frequency exponent in the Hooge equation and the nitriding time. For the second set, a specific sensor based on conductivity noise (at the nitriding temperature) was built for shop-floor experiments. Although two different types of noise were measured in these two sets of experiments, the use of the frequency exponent to monitor the process evolution remained valid.
在涉及（碳、氮、硫等的）扩散的制造工艺中，渗层深度的演变至关重要：整个工艺的成功与否取决于此参数。目前，渗氮通常要么采用“后处理”方法进行校准，要么通过间接测量（氢气、氧气、水 + 二氧化碳）来控制。在缺乏“原位”监测的情况下，工艺参数（气体浓度、温度、钢的成分、传感器与炉膛之间的距离）的任何变化都可能导致代价高昂的工艺效率低下或失败。间接测量可以防止工艺失败，但在测量参数与实际扩散过程之间的关系中可能会出现不确定性和复杂性。本文提出了一种基于噪声和波动测量的方法，该方法可直接控制渗层深度的演变，因为相关参数是在与渗氮钢（由活性电极表示）直接接触的情况下进行测量的。本文涉及两组相关实验。第一组实验包括对渗氮样品进行的实验室测试，使用巴克豪森噪声，得出了胡格方程中的频率指数与渗氮时间之间的线性关系。对于第二组实验，构建了一种基于（渗氮温度下的）电导率噪声的特定传感器用于车间实验。尽管在这两组实验中测量了两种不同类型的噪声，但使用频率指数来监测工艺演变仍然有效。
