Can the worn gears of a reverse gear be repaired by welding?

It is not recommended to repair worn reverse gear gears through welding, mainly for the following reasons:

1. Limitations of Welding Repair

Damage to gear performance caused by high welding temperature

Gears are usually made of medium carbon steel (such as 45 steel) or alloy structural steel (such as 20CrMnTi). These materials obtain high hardness (tooth surface) and toughness (tooth core) through heat treatment (quenching + tempering). The local high temperature during welding (arc welding temperature can reach above 1500°C) will destroy the original heat-treated structure:

The hardened layer on the tooth surface is "annealed" and softened, losing wear resistance;

Cracks may occur in the welding heat-affected zone (due to rapid cooling speed and concentrated internal stress in the material), leading to gear fracture under stress.

Difficulty in ensuring gear precision after welding

The meshing accuracy of gears depends on strict dimensions (tooth thickness, tooth pitch) and geometric tolerances (tooth direction, tooth runout). During welding, gears will deform due to thermal expansion and contraction, and the welded metal (such as electrode deposit layer) is difficult to ensure uniformity. Even if polished and trimmed subsequently, the original tooth profile accuracy cannot be restored. Meshing will cause impact, noise, and even accelerate the wear of other gears, leading to more serious failures of the reverse gear.

Insufficient welding strength, prone to secondary damage

When gears transmit power, the tooth surface bears large contact stress and bending stress. The bonding strength between the weld repair layer and the base material is low (especially when the welding process is poor, pores and slag inclusions are easy to occur). Under stress, it may fall off from the welding position, forming new "hard spots" or fragments, causing more dangerous failures such as gear jamming and tooth chipping.

2. More Reasonable Treatment Methods

Directly replace with a new gear

Gears are high-precision transmission components. Replacing with a new gear of the same model after wear is the most reliable solution, which can ensure meshing accuracy and service life, and avoid secondary failures caused by improper repair.

Temporary emergency repair in special cases (only for non-critical scenarios)

If a new part cannot be replaced temporarily, surfacing followed by machining can be tried (professional equipment is required):

First, anneal the worn tooth surface to reduce welding stress;

Use small current and segmented welding (such as argon arc welding) to reduce deformation;

After welding, reheat treat (quenching + tempering), and trim the tooth profile with a milling machine or grinder.

However, this method has high cost and difficulty in ensuring precision, so it is only suitable for temporary emergencies, and new parts still need to be replaced for long-term use.

Summary

After the reverse gear gears are worn, welding repair is not only difficult to restore performance but also may bring safety hazards. Replacing with new gears is a more reliable choice. For key transmission components, their precision and strength should be prioritized to avoid greater failure risks due to cost savings.