Development of adhesive-soft solder hybrid bonding method and its application to cutting tools

The joint methods using adhesives have widespread applications in today's industry. However, the process is preferable due to its convenience and feasibility, the joint strengths depending on adhesive materials. It is possible to increase the mechanical strength of adhesive joints by adding metal powder at various sizes into the adhesive material. In previous studies, the effects of the added metal powder were investigated with the assumption of not changing the structure of metal powders. In this study, soft solder alloy powder was added into the adhesive that is cured by temperature. New hybrid bonding method is developed by exploiting lower melting temperature of the additive powder compared to the adhesive curing temperature. In this hybrid method, bonding and soldering processes are implemented together. Steel to steel and steel to hard metal pieces were bonded with the new hybrid method. In steel to steel and steel to hard metal hybrid joining processes, shear strength of joints done by %5 soft solder powder additive adhesive at 200 °C furnace temperature is higher than joints done by same percent soft solder powder additive at 180 °C furnace temperature. However, shear strength increase provided by this new hybrid method on steel to hard metal piece joints is higher than on steel to steel piece joints. In steel to steel and steel to hard metal hybrid joining processes, shear strength of joints made by %5 soft solder powder additive adhesive at 200 °C furnace temperature is higher than joints made by same percent soft solder powder additive at 180 °C furnace temperature. However, shear strength values provided by this new hybrid method on steel-hard metal joints are higher than values obtained by applied to steel-steel pieces. The developed hybrid method was applied to cutting tools used in machining. To attach the inserts to tool holder, generally, mechanical fastening, hard soldering and adhesion methods are used generally. It is known that bonded tools have more advantage than tools made by other joint methods in terms of work piece surface quality. However, strengths of the bonded cutting tools are limited. By taking advantage of machining performance properties of bonded tools insert was attached to tool holder with the new developed hybrid method. In the experiments, it is observed that both soldering and bonding occur at the same time on the joint bonded with hybrid joint method. By making turning experiments of 1050 steel used cutting tools which was attached by new hybrid method and mechanical fastening method, cutting forces, temperatures and work piece surface roughness were measured and the results of both different joints methods were compared. In the experiments, by increasing of cutting speed, cutting forces of tools attached with bonding-soldering method occurred higher in comparison tools with mechanical fastening method. At the minimum cutting depth (1.5 mm) used in the experiments, temperature measured at the interface layer and work piece surface roughness on tools attached with bonding-soft soldering method was less than on tools attached with mechanical fastening depending on the increasing of cutting speed and feed. In this study, new hybrid method (bonding-soft soldering) is developed; it is determined that this method is applicable and provide higher strength than bonding and bonding-metal powder joining methods. Also, the method has been used in cutting tools and it is seen that method can be applicable to finish and specially metal cutting which desire high surface quality.