Hydraulic columns have been corroded by acid and alkaline media for a long time and operate in harsh, heavy-load, vibration, impact, and other environments. Their surfaces are easily prone to failure due to severe wear, corrosion, and other factors. Laser cladding of failed columns can restore their size and function, which can effectively extend their service life.

Repair case:

Hydraulic columns have been corroded by acid and alkaline media for a long time and operate in harsh, heavy-load, vibration, impact, and other environments. Their surfaces are easily prone to failure due to severe wear, corrosion, and other factors. Laser cladding of failed columns can restore their size and function, which can effectively extend their service life.

Skills requirement:

1. The cladding layer and the base material are metallurgically bonded, and the cladding layer has no defects such as cracks, pores, or lack of fusion;
2. The thickness of the cladding layer reaches 0.6MM;
3. The cladding efficiency is not less than 0.4 square meters/hour;
4. The corrosion resistance and wear resistance of the cladding material meet the requirements for column use in the coal mining industry.

a) Technical requirements for laser cladding of outer circumference of columns:

1. There are no visible cracks, slag inclusions, pores, and other defects;
2. The pore diameter on the surface of the cladding layer is not greater than 0.2mm, and the pores are ≤ 5 points/dm²;
3. Dimensional testing: Surface hardness HRC: 50~55, surface roughness ≤ 0.4μm, straightness ≤ 2‰, cylindricity ≤ 0.02mm;
4. Non-destructive testing:
   100% MT testing, implementing standard ISO17638-2003
   100% UT testing, implementing standard ISO11666-2010

b) Technical requirements for inner hole repair:

1. The cladding layer has no defects such as pores, slag inclusions, cracks, and missing meat;
2. Dimensions must meet the requirements of the original design tolerance level ΦDH9, as required by the drawings;
3. The chamfer of the inner hole has a smooth transition, with a chamfer of 6×20°;
4. Coaxiality with inner hole ≤ 0.05mm;
5. Inner hole surface roughness ≤ Ra0.4;
6. Detect the hardness of the inner hole cladding layer HB180 ~220.

Technical plan for laser repair of column outer surface

The laser cladding process is used to repair the corrosion on the outer surface of the column. Two laser claddings are used: 1. Cladding of the base layer (depending on the corrosion of the column); 2. Cladding of the corrosion-resistant and wear-resistant layer (the column is corrosion-resistant). Wear-resistant laser cladding special powder).

Metallographic and hardness testing

After cladding, use wire cutting to cut along the direction perpendicular to the laser scanning, cut into metallographic specimens, grind and polish, corrode with picric acid, then rinse with alcohol and blow dry. Use a metallographic microscope to observe the metallographic structure.