Effect of heat treatment on hardness and wear behavior of weld deposited Co-Cr-Mo alloy

Abstract

Metallic materials are generally characterized by the evaluation of hardness and wear resistance of the material at the specified condition. The characterization is necessary for understanding the behavior of the metals, especially alloys, at different conditions. To study the effect of heat treatment on weld deposited Co-Cr-Mo alloy, arc welding process has been used to prepare the samples.Using L9 Orthogonal array of Taguchi method, the samples, in three groups,are heat treated by solution at 1200 o C for 30, 45 and 60minutes followed by water quenching. Two sets of the samples from each groupare aged at 815 o C and 830 o C for 2, 4 and 6 hours. All the samples are then tested for their hardness andwear resistances. Microstructure analysis has been carried out from SEM images of the samples. The experiment results reveal that the differences in heat treatment did not influence the grain size of the samples, but the precipitation of carbides varies from sample to sample. The CoCr-Mo alloy samples solutionized at 1200 o C for 60minutes have exhibited high hardness (371.6±2Hv) and wear resistances. For high hardness and wear resistance, high solution time is required. ANOVA has been carried out to identify the best parameters of heat treatment. Key words: Co-Cr-Mo; welddeposition;solution heat treatment; ageing;microstructure; hardness; wear resistance ____________________________________________________________________________________________________ INTRODUCTIONCharacterization of a material is done generally by conducting a series of tests on the material like hardness, wear resistance and microstructure analysis. The behavior of Co-Cr-Mo alloy was also analyzed at different conditions of the material samples.The results of the experiments conducted on Nickel and Carbon free Co-Cr-Mo alloy by applying heat treatment followed by hot forging process reveal that the yield strength of the material decreases with increase in heat treatment temperature and time [1].The optimal results of mechanical properties were obtained at an ageing temperature of 815 o C for 4 hours and solution at 1120 o C for 1 hour on as-cast Co-Cr-Mo samples. The mechanical tests showed that an excessive time of dissolution reduces Ultimate Tensile Strength [2]. Dense components of Co-Cr-Mo were fabricated using laser deposition method, by optimizing the process parameters.The carbide volume fraction and the hardness were comparable with wrought material, but the abrasive wear resistance of laser deposited samples was less [3].Thephase and shape of the carbide precipitates depend on the carbon content and the type of heat treatment. Shingo Meneta et al have tested ASTM 75 confirming CoCr-Mo alloy samples with four different carbon contents for their microstructures after applying solution heat treatment in the temperature range of 1200 o C to 1275 o C for the time periods of 0 to 12hours. A new π phase has been identified in the alloys with carbon content 0.15, 0.25 and 0.35 mass percentage, after heat treatment at high temperature (...

Weldability Study of LM25/ZrO2 Composites by Using Friction Welding

“…It is observed that as the percentage of reinforcement increases the area fraction also increases as shown in the micrographs. Similar trends have been observed by many other researchers [11].…”

“…It is observed that the hardness values of the material are directly proportional to the presence of ZrO 2 and with the increase in ZrO 2 , the hardness value of the composites increases .The above graph shows the variation of Brinell hardness value for different compositions of ZrO 2 in LM25/ZrO 2 composites. Similar trends have been observed by many other researchers [11,13].…”