1 Introduction The quality of the mold is closely related to the quality of the part. The surface of many molds (such as die-casting molds) must be plated to improve corrosion resistance, wear resistance, oxidation resistance and hardness. Although the traditional chrome plating technology is mature and the quality is relatively stable, because hexavalent chromium is a toxic substance, it seriously pollutes the environment. Therefore, eliminate pollution, protect the environment, clean production, and take the road of sustainable development. Electroplating nickel-tungsten alloy is a good choice for improving mold quality, extending mold life and cleaning production. Nickel and tungsten metals have high hardness, good wear resistance, and high adhesion temperature to the molten substrate. The nickel-tungsten alloy coating has fine crystal brightness, good wear resistance, strong bonding strength with the substrate, high hardness, and Vickers hardness of 1000 or more at high temperature. This technology has attracted the attention of all parties in recent years and will gradually replace the mold chromium plating. However, the technology currently has defects such as rough coating, unevenness and pitting, which seriously restricts its application development. 2. Plating solution and process The plating solution is mainly composed of sodium tungstate, nickel sulfate and sodium citrate, and the content thereof is 40 to 45 gL, 20 to 30 gL, and 40 to 50 gL, respectively. Process flow: Sand blasting → inspection → degreasing → cleaning → plating → inspection 3. Analysis of coating quality defects and their causes Common defects in nickel-tungsten plating are pitting, and the surface and spherical coatings are rough with white particles. The central plating is severely uneven with the sides, corners and R, and even fine cracks appear at the corners and R. 3.1 Pitting Pitting is a tiny white, black point-like defect on the coating. It has various shapes, some obvious and regular, easy to find, and relatively good control. A small amount of the naked eye can't be seen, and can only be inspected by instruments. Cause Analysis: The mold base is caused by bad sand, pores, pitting, adhesions, etc.; the mold adheres to the sand when sandblasting, or the sand is bad, or the sand is caused by impurities, oil, foreign matter, dust, etc.; Emulsified material when it is adhered, impurities in water during cleaning, etc.; caused by contamination of compressed air, pure water and its piping, tools, and impurities in the environment; undissolved salts in plating solution and activation solution Particles, acidified electrode metal, etc. can cause pitting. The above-mentioned pittings are visually visible, and some thin layer adhering substances on the surface of the mold are mainly analyzed as carbon compounds in the contaminated sand before plating. It is firm and its adhesion is gradually becoming a high-viscosity gel that is resistant to acids and alkalis and vibration. It is not easy to remove during degreasing and cleaning. Once it is negligent, it flows into the electroplating process, which is inevitably covered by the coating. It is difficult to find and can not be compensated by the naked eye. 3.2 Rough plating Cause Analysis: The basic composition of the plating solution is nickel sulfate, sodium citrate, sodium tungstate, etc., as well as salts, organic complexes and the like. The test found that the defects of the mold plating are mainly related to the impurity content in the plating solution. The purity of the chemical is not high, the foreign matter in the plating solution, and the frequent use of the plating solution make the content of the metal impurities Cu, Fe, Cr, Co in the plating solution exceed the allowable range, etc., which may result in rough plating, increased pitting, and white. Particles. 3.3 The thickness of the coating is severely uneven The plating at the center and the side, corner, and R is severely uneven, and even fine cracks appear at the corners and R. Concerned about surprises Label: Die life Plating Tungsten alloy Plating chrome Die casting mold Previous: What is a DC geared motor? Next: Hardware locks monopoly chain circulation pattern is changing Aluminum Spiral High Speed Doors Aluminum spiral high speed door is the highest grade industrial door. It owns all possible advantages, including fast running speed, thermal insulation, noise isolation, and excellent wind-resist. So, no matter where you need install doors in your factory, warehouse and commercial buildings, such spiral aluminum rapid rolling doors can meet all your requirement. Spiral high speed doors, Aluminum high speed doors, Metal high speed doors, Insulated high speed doors, Spiral rapid doors SHANGHAI KENVO DOOR CO.,LTD , https://www.kenvodoor.com