Laser cladding rapid manufacturing technology is a kind of new developed advanced manufacturing technology integrating the advantages of rapid prototyping manufacturing and laser cladding surface modification. Due to the complex thermo-physical and metallurgical factors in the deposition process, the cladding layer is liable to crack, which seriously impedes the industrial application of this technology. Experiments of laser cladding rapid manufacturing 316L stainless steel were carried out. The cracking behavior and phenomena has been observed, cracking mechanism of 316L stainless steel was investigated by means of microstructure characterization and phase analysis with optical microscopy (OM), X-Ray diffraction (XRD), scan electronic microscopy (SEM) and phase diagram analysis. Factors influencing the cracking susceptibility has also been studied. Results show that the cracks of 316L stainless steel were hot solidification cracks caused by the high residual stress and separating of the liquid films among dendrites. Through the optimization of process parameters, adding protective atmosphere, etc. cracking sensitivity has been effectively reduced and crack free 316L stainless steel components have been obtained.

The CCT curve and TTT curve of as-cast 42CrMo steel were precisely simulated by using JmatPro software. The quenching process(which is as follow: quenching at 860°C by AQ251 quenching liquid and cooling to 200°C) was given by analysizing the CCT curve. The quenching microstructure, hot-stress field and hardness after quenching were simulated by using the Deform-HT module The results were obtained as follows:(1)The microstructure of the materials is martensite+bottom bainite at the surface and pearlite+ferrite at the centure.(2)The surface hardness and central hardness were separately 51.3 and 28.5 HRC. The metallographic observation and hardness experiment were done and the results of numerical simulation was finally verified.

The purpose of this study is to find the hot deformation behavior of as-cast 42CrMo steel. The thermal simulation experiments of as-cast 42CrMo steel were done on the Gleeble-1500 thermo-mechanical simulation machine. The hot deformation behavior of as-cast 42CrMo steel was analyzed. The true stress-strain curves in hot deformation at different deformation temperature (850°C,950°C,1050°C,1150°C), different strain rate (0.05S-1, 0.5 S-1, 1 S-1,5 S-1) were obtained. The influence rules of the deformation temperature and strain rate on the curves were analyzed. The analysis shows that the true stress increases with increase of deformation temperature and decrease of stain rate. The hot deformation behavior of as-cast 42CrMo steel was compared with forged 42CrMo steel. The results show that the flow stress of as-cast 42CrMo steel during hot deformation was higher than that of the forged 42CrMo steel. Compared to the forged 42CrMo steel, the dynamic recrystallization in as-cast 42CrMo steel during hot deformation is more difficult to occur. The above conclusions have significant theoretical and practical meanings for the design of hot deformation process of as-cast 42CrMo steel.

The numerically simulation of temperature field was carried out by the ANSYS software in multi-layer powder-feeding laser cladding forming.3-D finite element model was found, which nonlinear characteristics of the material thermal properties and the boundary conditions of the convective transfer heat was considered; The process of powder falling into the substrate and cladding element growing was accomplished by “Element Birth and Death technology” in the process of numerical simulation. The result shown that the primarily solidified cladding layer to the following cladding layer has a preheating function in the process of multi-layer laser cladding forming, the initial temperature of following cladding layer is higher than primarily melted cladding layer; The thermal cycling curves of the molten pool nodes takes on periodic variation and basic similar in every layer cladding; The end effect problem is apt to happen in cladding layer, which the phenomenon of edge collapsing or partially burnt is formed; The temperature gradient distribution is divided into two parts, the temperature gradient level distribution along the laser scanning direction in the top and perpendicular distribution in the bottom, The temperature gradient appearances mutation and maximum value in the junction of the substrate and cladding layer, which the crack is apt to be caused in this region.

Cold rolling precision forming process of spline is one of the high-efficiency, precision and non-chip forming advanced manufacturing technologies. It has the characteristics such as high forming efficiency, energy-saving, low material consumption and better forming properties of components. The process and principle of involute spline cold rolling precision forming was analyzed. A measuring and testing system for the force and energy parameters in the forming process was set up, and the real-time variation curves of the torque moment of the spindle and the radial feeding force were obtained. Also, the influencing rules of process parameters on the maximum radial feeding force and spindle torque were investigated. Finally, Precision forming experiments of involute spline cold rolling were carried out with optimized parameters. Precision measuring and hardness testing of the tooth outline section shows that the components obtained by the experiments were free of defects. Compared with the spline components obtained from conventional cutting process, the hardness and wear ability was greatly improved, which is suitable for the requirement of application.