Laser cladding of Stellite1 on AISI 4340 steel

In this project, deposition of Stellite1 on AISI 4340 steel is studied. Cobalt-based/carbide type alloys, also called Stellite alloys, are well-known for their “hot hardness” which is their capability of functioning in high temperature environments without compromising their hardness. Therefore, these alloys are extensively used for hardfacing of components mainly pertainin. However, the main challenge in deposition of Stellite 1 using laser cladding is crack sensitivity of this alloy during hardfacing process. To alleviate or possibly eliminate the potential crack formation across the deposited material, the effect of preheating the substrate prior to the deposition process is investigated as a means of reducing the thermal stresses induced during the hardfacing process. 

Clad height control 

In laser cladding, clad geometry is a function of several process parameters as well as physical phenomena occurring in the course of the process.Therefore, monitoring and controlling these parameters throughout the process is of critical importance in achieving a clad with desirable geometrical and metallurgical characteristics. In this project, a closed-loop control strategy is developed to control the clad height during the process. 

In-Situ TiC-Fe deposition on mild steel

An alternative approach to producing a very hard wear surface is to form the metal/ceramic composite during laser cladding. In-situ laser cladding enables the formation of a uniform composite from pure premixed powder components. Since TiC has desirable properties such as hardness, wear and corrosion resistance, titanium (Ti) and graphite (C) are used as a composite material (i.e., TiC) to increase hardness and wear resistance of AISI 1030 carbon steel. In this project, effects of laser parameters such as laser power, scanning speed, and powder feed rate on clad quality are studied. Results demonstrate the importance of aforementioned process parameters on TiC distribution pattern and metallurgical bonding between clad and substrate. 

Development of new tool materials by laser cladding of diamond matrix composites on body substrates

Diamond particles embedded in a metal binder are very effective cutting materials. However in bulk form they are very expensive. To reduce the cost, the cutting edges of the tool can be built on cheaper and non-brittle body substrates. Studies will be conducted to understand the deposition of pre-mixed diamond/metal powder on other materials such as tool steel to develop a new approach in tool fabrication. 

Characterizations of Tungsten Carbide laser cladding

In this part of the project, laser cladding characterizations will be conducted to investigate the influence of various process parameters on the mechanical and metallurgical properties of the deposited tungsten carbide mixed in liquid matrix (i.e., Co and Ni-based alloys) on different tools substrates. In this study, the process parameters such as laser pulse energy, laser pulse frequency, laser pulse width, table velocity, laser spot size on the workpiece, and powder feedrate will be adjusted to arrive at optimum solidification rate, high density and a strong metallurgical bond between the clad and the substrate. This study of controlling the process parameters aims at minimization of interaction time between the laser beam and liquid matrix, which in turn prevents the shape and size of WC particles from any microstructural changes. If successful, the output of process parameters’ control paradigm will be the cladding of cutting tools with layers of WC in a matrix, in which the microstructure of WC in the matrix will not be altered.

Path planning

In laser cladding, the deposition path generation is dependent on the nature of the deposition process. As a result, the properties of the deposited materials are influenced by the deposition path trajectory. Thus it is important to develop and appropriate path planning to reduce the path effect on the mechanical and metallurgical characteristics of the parts. One of the factors that limits the quality of parts in laser cladding is the accumulation of residual thermal stresses. It is possible to reduce this effect by selecting appropriate deposition paths.

In this part of project, path generation will be characterized to address the required quality in the repaired tools. This task will be carried on by examining various path classes on different defected regions in the tools. Temperature will be measured by pyrometers to assess the temperature gradient over the tools at different path planning. By optimization of temperature gradient, the quality of tools will be increased which in turn results in stronger metallurgical bond and desired metallurgical and mechanical properties.

Repair of cemented tungsten-Carbide tools by directly depositing pre-mixed tungsten-Carbide/Co powder using laser cladding 

The above studies will be used to understand cladding of premixed tungsten-carbide/Co powder on cemented tungsten-carbide substrates. In addition, bonding strengths with respect to material compositions and laser parameters will be identified for automatic tool repair. We also conduct process optimization to achieve repeatable and high quality tungstencarbide/ Co clad. Our industrial partner will evaluate and test the repair tools and their feedback will be used to fine tune the process. We further enhance our controller to achieve an automatic tool repair.

Development of less expensive non-brittle tools by building cemented tungsten- Carbide cutting edges on body substrates using laser cladding

Cemented tungsten-carbide tools are brittle and expensive. To reduce the cost and brittleness, the cutting edges of the tool can be built on a cheaper and non-brittle body substrate. Studies on deposition of pre-mixed tungsten-carbide/Co powder on other materials such as tool steel will be used to develop a new approach in tool fabrication. Graded deposition will also be examined for improving bonding strength between the substrate and clad. The tools fabricated by our lab will be grinded and tested by the industrial partner for evaluation.