Problems that are prone to occur during high-speed laser cladding process and analysis of their causes

(1) Peeling
This is due to the lack of molten pool formation in the matrix, and the lack of metallurgical bonding between the powder and the matrix. Possible reasons include: low power; Excessive powder content; The linear speed is too fast; The surface of the workpiece may have oil stains or electroplating layers.

(2) Cracks
The reasons for the appearance of cracks in the coating include: high hardness of the substrate (quenching, carburization/nitrogen); The matrix has a fatigue layer; The powder hardness is too high. Nickel based powder is prone to cracking; Cracks may also occur during multi-layer cladding of powder with high hardness.

(3) Stomata
The reasons for the appearance of pores in the coating include: rust and oil stains on the substrate; Impurities in the powder; Unstable powder flow; Excessive powder content; Insufficient power; Or excessive linear speed, etc.

(4) There is a lot of floating powder, and the coating has no metallic luster
Possible reasons include: excessive powder content; Power too low; The linear speed is too fast; The nozzle height is too high; The laser spot is too small; Lens contamination, etc.

(5) Pitting appears after grinding and polishing
Possible reasons include: insufficient power; Excessive powder content; Excessive linear speed, etc.
(6) The coating shows diagonal wrinkles
Possible reasons include: excessive power; The temperature of the molten pool is too high; Excessive liquefaction of powder.

(7) Nozzle sticking powder
Possible reasons include: powder ejection too high; The temperature of the copper head is too high; The working distance of the nozzle is too low, and the surface of the nozzle is too rough or contaminated (polishing treatment is recommended). Placing the fusion head off center is beneficial for reducing powder sticking.

(8) Clogging powder
Possible reasons include: the sticky powder was not removed in a timely manner; Poor powder flowability; Impurities or moisture (to be baked dry) in the powder. Uneven powder delivery across multiple routes is an important reason for powder blockage.

(9) There is a sizzling sound during melting
Possible reasons include: powder contamination; Wet powder; Unclean substrate, etc. Excessive power density can also lead to metal gasification in the molten pool, resulting in cladding noise. These issues will affect the corrosion resistance of the coating.

(10) Spark splashing during cladding
Possible reasons include: excessive linear speed; Excessive power density; Power and powder quantity mismatch; Excessive air flow rate, etc.

(11) Unstable powder flow, leading to uneven coating
The reasons for unstable powder flow include: large wear and tear on the scraper; The powder delivery channel is blocked; The airflow is too small; Poor sealing at the sealing ring of the powder feeder or damage to the powder feeding tube may cause air leakage, etc.

(12) Reduced melting efficiency (thinning of coating thickness)
Possible reasons: contamination of protective mirrors; Scraper wear and tear; Inappropriate working distance; The powder hole is enlarged by grinding, and the powder flows coarsely; Laser power reduction, etc.

Source: Guosheng Laser