Xiaobian will explain to you what are the problems and solutions that are prone to glow ion nitriding?

Compared with gas nitriding, glow ion nitriding has the advantages of fast nitriding time, small brittleness of nitriding layer, and saving ammonia consumption, but there are also some problems that often occur and are not easy to solve in actual production. This paper mainly introduces the common problems of glow ionic nitriding parts, analyzes the causes of the problems, and proposes solutions.

1. There will be uneven black bands along the corners, orifices, and top corners of the teeth of glow ion nitriding parts

Reason: Because the glow ion nitriding furnace does not have an independent second heat source or auxiliary heat source that can be arbitrarily controlled, it relies on ion bombardment heating, in order to achieve the nitriding process temperature, a strong glow is required, and the pulse duty cycle is often above 0.7 and tends to DC, resulting in strong effects such as sharp corners and hollow core cathodes, and decarburization is produced at a high temperature along the corners and orifices, while the large temperature difference in the furnace and the uneven distribution of the atmosphere make the black belt different.

Solution: The second heat source and its technology are added to the ion nitriding furnace, and the medium heat glow (medium glow intensity) or strong heat and weak glow can effectively inhibit the sharp angle and hollow core cathode effect, and the temperature of the furnace is controlled within ±5 °C, which basically solves the decarburization problem of these parts of the nitriding parts.

2. Soft bands will appear at the fillet and joints of glow ion nitriding parts

Reason: Because the glow ion nitriding furnace relies on strong glow heating to reach the nitriding process temperature, the glow overlap at the fillet and the junction plays a shielding role, resulting in the formation of soft bands; And the stronger the glow, the more obvious the soft band.

Solution: By adding the second heat source and its technology to the ion nitriding furnace, the medium and high intensity auxiliary heat source and medium and low intensity glow energy can be used to weaken the shielding to a very small size, and almost no soft belt is generated.

3. Glow ionized nitriding stainless steel valve parts are easy to rust after ionic nitriding

Reason: For 316L or two-way stainless steel and other valves or spheres to do ion nitriding, a strong glow is needed to reach the nitriding temperature, and above 420 °C, with the stronger the glow, the greater the ion bombardment and sputtering, resulting in the loss of chromium and carbon on the surface of the material, which is easy to be corroded.

Solution: The second heat source and its technology are added to the ion nitriding furnace, and the process production can be avoided by using a strong auxiliary heat source and a weak glow intensity under the condition that the temperature difference in the furnace is ≤±5 °C at the nitriding process temperature. However, it is necessary to pay attention to grasp the passivation film on the surface of stainless steel with medium and strong glow to eliminate the passivation film in the process of ≤ 400°C. Then turn on the auxiliary heat source and gradually reduce the glow intensity.

4. It is difficult for the large and heavy mold of glow ion nitriding to rise to the nitriding process temperature

Reason: This is because the glow ion nitriding furnace completely relies on the heat generated by the strong glow bombardment of the workpiece to heat the workpiece, and the ion heating is closely related to the surface area of the workpiece, and is also related to the large mold surface area and weight disparity, when the limited heating energy and the heat dissipation loss of the furnace reach a balance, the temperature in the furnace can not rise is an inevitable phenomenon, unless the performance parameters such as the limited voltage of the equipment are improved and the thermal insulation performance of the furnace is strengthened or auxiliary facilities such as cathode plates are increased.

Solution: The second heat source and its technology are added to the ion nitriding furnace, and the ion nitriding is no longer limited by the disparity between the surface area and the weight ratio of the workpiece. When the high operating temperature is 650°C, the temperature difference in the furnace is ≤±5°C, and it can also... At a high operating temperature of 950°C, the temperature difference in the furnace is ≤±5°C.

5. The nitriding effect of the glow ion nitriding furnace on titanium parts is not good

Reason: The glow ion nitriding furnace has the function of controlling the temperature difference in the furnace is missing. It is difficult to raise the temperature to more than 600°C under the condition of high voltage 1000V, and the temperature of the nitriding process should be above 650°C for the formation of TiN for titanium parts, and the smaller the temperature difference in the furnace, the better.

At present, some companies use the hollow cathode effect to do the nitriding treatment of small titanium parts in the glow ion nitriding furnace, which not only has high application cost, but also is difficult to stabilize production, and it is difficult to achieve the desired effect.

Solution: The second heat source and its technology are added to the ion nitriding furnace, which can well meet the temperature and uniformity requirements of the nitriding treatment of titanium parts, and has achieved good results in actual processing.

6. The parts after ion nitriding will be deformed out of tolerance

Reason: The deformation out-of-tolerance problem of parts after ion nitriding should be comprehensively analyzed and solved. First of all, it is necessary to look at the pretreatment of material and blank forming, that is, whether the stress relief annealing meets the requirements of the specification, and whether the machining stress after machining is annealed, and then whether the means and process, that is, the plasma nitriding equipment, meet the production requirements and whether the process is mature.

As far as the ordinary glow ion nitriding furnace is concerned, due to the need for strong glow heating and nitriding, the temperature at different geometries of its parts is different, and its heat dissipation is also different, which will produce thermal stress deformation; Moreover, it is related to the placement of parts and components, the design of tooling, and the lack of temperature control means in the furnace.

Solution: The second heat source and its technology are added to the ion nitriding furnace, because it has a second heat source system, it can effectively control the upper, lower, inner and outer temperatures in the furnace, so that the uniformity of the temperature in the nitriding furnace is greatly improved compared with the ordinary glow ion nitriding furnace, which is also the use of the second heat source or auxiliary heating. The root cause. With the improvement of temperature uniformity, the temperature difference between different parts of the same part will be greatly reduced, and the deformation caused by thermal stress will be controlled to a small extent.

7. Conclusion

To sum up, the use of a second heat source and its technology in the ion nitriding furnace can effectively solve the quality problems that are easy to occur in the production of ordinary glow ion nitride, which is the development trend of glow ion nitriding equipment.