Heat Treatment & Metal Joining

Plasma nitriding

A plasma supported thermochemical case hardening process used to increase wear resistance, surface hardness and fatigue by generation of a hard layer including compressive stresses.

The advantages of gaseous nitriding processes can be surpassed by plasma nitriding. Particularly when applied to higher alloyed steels, plasma nitriding imparts a high surface hardness which promotes high resistance to wear, scuffing, galling and seizure. Fatigue strength is increased mainly by the development of surface compressive stresses. Plasma nitriding is a smart choice whenever parts are required to have both nitrided and soft areas. The possibility of generating a compound layer free diffusion layer is often used in plasma nitriding prior to PVD or CVD coating. Tailor made layers and hardness profiles can be achieved.

Materials

Plasma nitriding is suitable for all ferrous materials, even sintered steels with higher porosity, cast iron and high alloyed tool steels even with chromium contents higher than 12%. Stainless steels and nickel based alloys can be plasma nitrided and keep most of their corrosion resistance if low temperatures are applied. Special applications are plasma nitriding of titanium and aluminium alloys. For heavy loads on large machine parts such as shafts and spindles, the use of special chromium and aluminium alloyed nitriding steels gives a huge benefit as plasma nitriding generates a surface hardness of more than 1000 HV.

Boriding

Boriding is a thermochemical surface hardening method which can be applied to a wide range of ferrous, non-ferrous and cermet materials.

The process entails diffusion of boron atoms into the lattice of the parent metal and a hard interstitial boron compound is formed at the surface. The surface boride may be in the form of either a single phase or a double phase boride layer.

Boriding provides a uniform hardness layer from the surface on to the entire depth of the diffused layer. The hardness achieved is many times higher than any other surface hardening process. The combination of high hardness and low coefficient of friction enhances wear, abrasion and surface fatigue properties. Other benefits associated with boriding are retention of hardness at elevated temperature, corrosion resistance in acidic environments, reduction in use of lubricants and a reduced tendency to cold weld.

Materials:

Boriding is carried out on most ferrous materials, with the exception of aluminium and silicon bearing steels, e.g. structural steels, case hardened, tempered, tool and stainless steels, cast steels, ductile and sintered steels and also air hardened steels. In addition, materials such as nickel-based alloys, cobalt-based alloys and molybdenum can be borided. Nickel alloy can be borided without sacrificing corrosion resistance, as well as producing extreme hard surface wear resistance. Steels which are not suitable for boriding are nitrided steels, leaded and resulfurised steels.

Electron Beam Welding (EBW)

Electron beam welding (EBW) is a specialist metal joining technique used to create high integrity joints with minimal distortion. Bodycote has the largest Electron Beam Welding (EBW) capability in Europe.

Advantages:

  • Low vacuum process, yields clean reproducible, high integrity joints
  • Low heat input with minimal distortion and a narrow heat-affected zone
  • Weld penetration of up to 30mm+
  • Metals of dissimilar melting points, sizes and thermal conductivities can be welded
  • Quantities from one-off development to large production batches can be accommodated