High tungsten stainless steel can be widely used in precision instruments, especially in aviation products. Electroplating hard chromium can improve the hardness, wear resistance and corrosion resistance of high tungsten stainless steel parts, but it is prone to leakage plating and partial thin defects. In this work, some special technological measures are adopted to ensure the quality of hard chromium electroplating for high tungsten stainless steel parts in aviation products.
1.1 Chrome plating process
Parts → blowing wet sand → alkaline degreasing → hot water washing → cold water washing → activation → cold water washing → chrome plating → hydrogen removal.
1.2 Pretreatment of chromium plating
1.3 Hard chrome plating
The parts should be immersed in hot water of 50 ~ 60℃ after pre-treatment to preheat, so that the temperature of parts and the temperature of hard chromium plating solution tend to be consistent. Parts should be charged to the groove, using small step current. Step small current size should be adjusted according to different areas. Step small current size should be reduced when the area is small, and step small current size should be increased when the area is large. For the parts with complex shape, the residence time of step small current used is longer, and the residence time is shortened with the increase of current, and the effect is very good.
2, the conclusion
The hard chromium electroplating process of high tungsten stainless steel alloy is special because of its high tungsten content. Two special methods are used to deal with it, namely, blowing wet sand and small step current, which stay for a long time. The leakage plating problem of the parts, especially the complex parts, is solved well, and the bonding force is good, and the damage to the stainless steel matrix is small. The hard chromium electroplating process meets the performance requirements: after the test piece is broken, no separation of chromium plating layer from the substrate; There are not more than 15 independent points or pits on a total area of 0.098m2 and the depth is not greater than 8.47×10-3m; Hardness is 850 hv or higher.
