Laser cladding of hard particles rich alloys

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Abstract
Under conditions of abrasive wear mechanism, hardness and grain size of the loaded material play a prominent part for the wear intensity. Generally, wear resistance goes up with increasing hardness and grain size of the material’s surface region. One way to get high abrasiv wear resistance is producing hard metal, that is the distribution of dense non-melted ceramic particles, mostly carbides, in a ductile metal matrix. In the case of the classic hard metal technique the hard particles, usually tungsten, titanium or complex carbides, are sintered with 1 to 5 % metallic binder (Ni or Co). Due to the high content of hard particles in the structure they determine the wear of the sintered carbide metal. The disadvantage of this technique is the need of a sinter process and that’s why a partially cladding of machinary components is not possible. The local cladding of metallic substrates with hard metal like materials can be realised by plasma spraying or deposition welding only. Plasma sprayed coatings can not often be applyed because of their insufficient bonding to the base material. In the range of deposition welding techniques the laser cladding process with pneumatic powder delivery is well suited to produce coatings containing high percentages of non-melted hard particles /1,2/. Using powder as added material nearly any desired mixtures of hard particles and metallic matrix alloys are possible. High heating and cooling rates and a short melt life put down the hard particle dissolution in the melt.

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