A study on wear behaviour of laser direct metal deposited high strength H13 tool steel

Laser assisted direct metal deposition (DMD) additive manufacturing process provides a realistic opportunity to create solid and porous structures from high strength metallic alloys that can be used as coatings, foams and sandwiched structures and as highly stressed components in contact with other metallic components. Very little studies seem to have been reported on the wear behaviour of parts fabricated by the laser DMD process in relation to various design parameters for various metals. This paper presents an investigation on the sliding wear behaviour of the DMD generated structures of high strength H13 tool steel using the pin-on-disc machine. The structures were machined and finished as pins for subsequent wear testing against a solid disc made of high carbon steel surface. The study includes effect on abrasive wear by variation of several design variables which include contact load, sliding speed and sliding distance. The mode of wear is chosen to be severe which consists of dry wear and speeds near or above 1 m/s. Wear volume and co-efficient of frictions are the two main wear parameters analysed in combination with the primary or design variables. The relationship between the design factors and the ensuing wear loss is discussed which proves the highly non-linear frictional behaviour. The results highlight a wear performance for laser generated H13 specimen that is strong and consistent although inferior to the wear behaviour of wrought tool steels. Despite lack of hot and cold working and any heat treatment, H13 specimens show little signs of micro-chipping and flaking under high loads

Dynamic behaviour of high strength steel parts developed through laser assisted direct metal deposition

High strength steel alloys are good candidates for many engineering applications particularly those involving high strains and impact loads. Such applications in energy absorption devices require materials that can sustain dynamic loading and remain strong under demanding conditions. But the processing cost of these alloys has been a prohibitive factor, thus re-enforcing the research on porous and cellular structures made of stainless steels. Direct metal deposition (DMD) is a process which employs the power of a CO2 laser to melt and deposit metallic powders onto steel substrates. Such structures offer advantages of creating novel configurations only by computer control of laser 'tool path'. This research investigates the mechanical behaviour of solid and porous parts with prismatic cavities under quasi-static and dynamic compressive loading. Apart from two main deficiencies of relatively large variations of properties among the test specimen and sufficiently low modulus of elasticity, the stress strain behaviour is very close to the commercial grades of stainless steel produced by rolling and forming. The energy absorption behaviour of porous specimen is also very encouraging and renders DMD as a suitable process for manufacturing of customized sandwich and graded structures that can be used as a substitution for many engineering applications such as monolithic compression plates and explosion shields

Dynamic behaviour of high strength steel parts developed through laser assisted direct metal deposition

High strength steel alloys are good candidates for many engineering applications particularly those involving high strains and impact loads. Such applications in energy absorption devices require materials that can sustain dynamic loading and remain strong under demanding conditions. But the processing cost of these alloys has been a prohibitive factor, thus re-enforcing the research on porous and cellular structures made of stainless steels. Direct metal deposition (DMD) is a process which employs the power of a CO2 laser to melt and deposit metallic powders onto steel substrates. Such structures offer advantages of creating novel configurations only by computer control of laser “tool path”. This research investigates the mechanical behaviour of solid and porous parts with prismatic cavities under quasi-static and dynamic compressive loading. Apart from two main deficiencies of relatively large variations of properties among the test specimen and sufficiently low modulus of elasticity, the stress strain behaviour is very close to the commercial grades of stainless steel produced by rolling and forming. The energy absorption behaviour of porous specimen is also very encouraging and renders DMD as a suitable process for manufacturing of customized sandwich and graded structures that can be used as a substitution for many engineering applications such as monolithic compression plates and explosion shields