since you have not mentioned your stream i assume it from EE or ME the vacancies in BHEL lies somewhere around 30 for ELECTRICAL and 20 in MECHANICAL

The GATE cutoff needed is on the higher side and only those in the top ranks stand a high chance of being called for the interview. On a general note, the number of candidates called for the interview is 4 times more than the actual requirement. Top rankers choose the company they will join so PSUs always call extra candidates. Above GATE scores is cutoff for a call to interview. Some PSUs like Powergrid also consider the performance of the candidate. Most PSU recruitment depends on GATE scores

These are the PSUs which take gate score for recruitment and if you want to know to apply there after M.Tech then kindly go through the criteria given on their official website.

And to know more about PSUs you can go through below article -

PSU Recruitment through GATE 2017

Hope this helps!!!