2. Boriding
Boronizing, also known as boriding, is a case hardening diffusion process where boron atoms are diffused into the surface of a metal component. This forms hard, metal-boride compound layers under the surface of a component. Boronized parts have two-five-times longer wear life compared to other heat treatments, such as hardening, carburizing, nitriding, nitrocarburizing or induction hardening.

3. Properties of Boronizing
Extremely high wear resistance (erosion or abrasive wear)
Galling resistance
High surface hardness ( HV for ferrous materials, HV for nickel-based alloys)
Boride layer depths can range from " to 0.015" deep depending on base material and processing parameters selected.
High-temperature resistance with up to 1200F service temperature possible with no adverse effects or degradation of the boride layer
Increased corrosion resistance to acids
Reduced coefficient of friction
Wide range of materials possible for treatment
Able to be combined with other heat treatment processes such as carburizing, hardening, induction hardening, austempering to develop deeper case depths and improved core properties below boride layer
Able to be selectively applied

4. Advantages: Disadvantages:
Increases resistance of low alloy steels to sulphuric, phosphoric, and hydrochloric acid
Increases resistance of austenitic stainless steel to hydrochloric acid
Selective hardening is possible
Can be polished to high finish
Can be applied to irregular shapes
Increases tool and mold life by improving resistance toabrasive, sliding and adhesive wear
Low coefficient of friction
Disadvantages:
Distortions due to high temperature
Poor fatigue and corossion resistance

5. Applications: Materials Suitable for Boronizing
1_Due to high hot hardness and wear resistance: Hot forging dies, wire drawing dies, extrusion dies, straightening rolls, ingotmolds et
2_Nozzles, plungers, gears, shafts and rollers
3_ Oil and gas components like valve components, valve fittings, metal seals, coal/oil burner nozzles
4_Turbine component.
5_Pump impellors ,ball valves and seats.
6_Shaft protection sleeve and guide bars
Materials Suitable for Boronizing
Plain carbon steels.
Alloy steels.
Tool steels.
Cast iron, ductile iron.
Nickel-based superalloys.
Cobalt alloys.
Stellite.

6. Alloying: Laser alloying :
Formation of homogeneous chemical compositions and phases within the modified surface region.
Laser alloying :
It is a surface modification technology in which the alloying elements are deposited on the substrate surface and then irradiated by a high energy laser beam. This causes rapid melting and mixing , so that the alloy elements and ceramic material disperse. In a very short period of time, cooling and solidification form a thickness of 0.1_0.5mm of a new alloy layer.

7. Purpose : Features of the alloy layer and the substrate :
Have strong binding force.
High hardness.
Good wear resistance. 
Laser surface alloying is attractive ?
because of the wide variety and microstructural states that can be retained because of the rapid quench from the liquid phase. These include chemical profiles where the alloyed element is highly concentration over shallow depths (hundreds of nanometers ),and uniform profiles where the concentration is the same throughout the entire melted region.
Purpose :
Is to provide specific microstructure and chemistry And to improve corrosion resistance such as in plain carbon steel by alloying with chromium and \or nickel. Alloying of ferritic stainless steel with molybdenum as well as Mo + B has been found to yield improved abrasive wear resistance.

9. The difference from surface melting process:
(LSA) is similar to surface melting with the laser except that desired alloying elements are extraneously added to the melt pool alter the surface chemical composition as best suited for the part being treated .
modification of the surface composition to achieve the desired properties can be effected by the alloying elements in:
gaseous
powder form as a prior coating .
Thickness of the alloyed layer can be up to 2000 ϻm.
Many factors must be considered in the laser alloying process.
These include:
Exposure time.
Laser power.
Thickness of the film .
Nature of the gaseous ambient during laser processing.
The processing variables are interrelated, and one variable cannot be freely changed without affecting another. Another consideration is that laser alloying is a liquid _state , rapid quenching phenomenon. The near surface region must be melted and yet vaporization avoided.
Laser alloying also involves very large temperature gradients and quenching from the liquid state. In this way it resembles other rapid solidification technologies.