Boriding

Boriding

Boriding is a thermochemical surface hardening method that can be applied to a wide range of ferrous, non-ferrous, and cermet materials and is designed to improve the life and performance of metal components.  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.

The process is a two-step reaction. The first step reaction is between the boron-yielding substance or compound and the part, which is a function of time and temperature. This results in a thin dense boride layer. This reaction is followed by diffusion, which is a faster process. The process is predominantly used to strengthen resistance to corrosion and abrasive wear, decrease the coefficient of friction, and significantly increase surface hardness.

At MTE, we make use of a specially formulated Boron-yielding powder which when heated to temperatures between 700 – 1000oC, result in boron atoms diffusing into the substrate forming extremely hard borides in the surface layers of the material.

The depth of diffusion and hardness is time, temperature, and material dependent, but one can achieve depths of 0.12 – 0.5mm and hardness’s of 1400 – 1900 HV.

Benefits

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 temperatures, corrosion resistance in acidic environments, a reduction in use of lubricants and a reduced tendency to cold weld.

Application

Boriding can be carried out on most ferrous materials, with the exception of aluminium and silicon bearing steels. Steels that benefit from boriding are structural steels, case hardened, tempered, tool and stainless steels, cast steels, ductile and sintered steels, and air-hardened steels. In addition, materials such as nickel-based alloys, cobalt-based alloys, and molybdenum can be borid. Nickel alloys can be borid without sacrificing corrosion resistance, in addition to producing extreme hard surface wear resistance.