How to Improve Defects in Metal Powder Metallized Ceramics? (2)

2. The Defects of Nickle (Ni) Coating:

(1) Sintering and blistering of nickel plating layer; The prime reasons are:

a. After sintering, due to long time exposure to the air of the metallized layer and the surface layer is easy to be slightly oxidized, resulting in bubbles after sintering of the coating;
b. Metallized layer pollution, plating solution is polluted;
c. When electroplating, the initial current density is too large;

Improvement methods mainly include as follows:

a. After metallization, the porcelain should be kept clean and arrange nickel plating process as soon as possible;
b. Regularly check and adjust the plating solution;
c. When electroplating, the initial current is appropriately reduced (for example, it is 2/3 to 3/4 of the normal electroplating current density).

(2) The root cause for rough surface after the nickel plating as the following
a. Excessive ampere density and too fast deposition rate of nickel ion;
b. Too high sintering temperature of the metallized layer may form Mo-Ni alloy already;
c. The composition of the electroplate liquid changes;

The improvement methods are to reduce electroplating current density, to reduce sintering temperature and test & re- treat electroplating solution.
defects for ceramic metallization 3

3. Defects of Finished Metallized Ceramics:

1). Black spots and yellow spots appear on surface of Metallized Ceramic Parts for the following reasons:
a. Crystals (impurities of ceramic compound) such as calcium-aluminum feldspar are transformed into gray spots under the condition of long-term heat treatment at high temperature due to phase change.
b. There are more variable valence ions in Advanced ceramics, such as Ti, Fe, Mn, etc., which are easy to produce black & yellow spots under high temperature and strong reduction conditions;

The main improvement method as below:
a. Shorten the high temperature heating time as much as possible,
b. Meticulously select the raw materials for Technical Ceramics in the production
c. And adjust the ceramic composition properly.

2). The below factors are for what the surface of the metallized porcelain is getting gray and black:

a. The metallized layer and molybdenum wire heater are oxidized seriously, which resulting in blacken ceramic surface;

b. The serious pollution of furnace chamfer & furnace tube, and the material volatilization, especially carbon deposition, make the black ceramic surface;

d. Ceramic setter plate, corundum sintering media and too many multiply use of these auxiliary material are resulting in volatilization of adsorption.

Improvement measures are not only to control the production of molybdenum oxide, but also to avoid the deposition of carbon, furnace tubes, furnaces chamfer, ceramic setter plate etc., should be cleaned and replaced periodically.

3). After metallization, there are the following reasons which result in deformation and cracking of Ceramic parts:

a. The thin wall thickness, the uneven wall thickness, and significant change of regional wall thickness are mostly easy to cause deformation or cracking;
b. The product is easy to deform when placed uneven in the Ceramic Sagger tray ;
c. Both oversintering and too long holding time in the furnace are easy to cause deformation.
d. Changes in the composition of ceramic materials;
e. The furnace heating rate and cooling speed are too fast, which will also cause ceramic parts to crack;

In order to prevent such defects as cracking and deformation, the first is to select quality fired ceramic parts, rationally design the structural shape, reduce stress concentration, and try to be uniform in thickness. In the process, the heating and cooling rate should be proper, and the atmosphere of metallizing should be adjusted. When placing ceramic components on ceramic setter plate and sagger tray, it should be properly fixed and as flat as possible according to the shape and complexity of the structure.

JingHui Industry Ltd is a professional manufacturer of Metallized ceramics, the comprehensive production capabilities and skillful, veteran & well-trained manufacturing team is our core competition, every pieces flow to our customer must be inspected rigorously to reach fix theirs challenge.