Strengthening and Reconditioning Methods

For many years NII Stali has been dealing with strengthening and reconditioning of engine and running gear components of domestically produced armored vehicles. Nowadays some of the methods are used in those civil industries which impose stringent durability requirements upon their equipment.

Below a number of methods currently used for civil purposes are presented.

Gas-thermal spray reconditioning Electropulse reconditioning and strengthening

Gas-thermal spray reconditioning

Main fields of application: Protection and hardening of working surfaces of parts operating under extreme conditions (high wear, elevated temperatures, aggressive media) Restoration of dimensions of worn-out parts with concurrent hardening of the parts at 30-70% of the cost of newly manufactured ones Production of skin pieces (e.g. press moulds for plastics etc.) Decorative and corrosion-resistant coatings Coatings - solid lubricants Protection against elevated temperatures (up to 2000°K) and increase of heat-exchange in refrigerating units

MAIN FEATURES

• 3-5 times higher durability as compared to hardened steels
• Thermal conductivity: from 0.7 to 200 W/mЧdegree
• Corrosion resistance in aggressive media
• Friction coefficient can be adjusted in the range of 0.05-0.35
• Coating thickness: from 0.1 to more than 30mm
• Spraying rate: from 3 to 25 kg/hr
• Applied materials: steels and alloys, non-ferrous metals, ceramics, polymers etc.
• The coatings can be spayed on all kinds of metals, wood, plaster, plastics, cardboard etc.

Main advantages:

• Can be used for reconditioning of heavily worn-out parts (sprayed coating thickness: 2-5 mm)
• Minimum heating of the part in the process of reconditioning which eliminates shrinkage of thin-walled parts.

The method has been proved for reconditioning of guide vane assemblies of centrifugal submersible oil pumps and wheel drums of Volvo trucks.

Status: Pilot technology

Electropulse reconditioning and strengthening

Parts strengthened by electropulse method.

The method is designed to improve wear resistance and load-bearing ability of heavy-loaded friction unit components and to recondition worn-out part mounting surfaces. The method implies electropulse surface treatment by innovative equipment which can be used in automatic line production due to its high reliability and durability. A special pulser and processing units are used to apply a metal layer of any composition on the work piece which imparts the required wear resistance and strength to its surface. The pulse mode of coating application minimizes heating of the work piece. The method enables reconditioning of parts operating under impact and fatigue loading with retention of their structural strength.

The method ensures the following:

• Increase of the service life of strengthened parts made of structural steels and titanium alloys by factors of 3-5.
  
• Increase of the load bearing ability of friction units up to 50-80 MPa.
  
• The desired friction factors in the range of 0.07-0.7 for dry friction and 0.03-0.2 for lubricated units.
  

Status: commercial technology